National Instruments Network Card SCXI 1503 User Manual

TM  
SCXI  
SCXI-1503 User Manual  
March 2007  
374271A-01  
 
 
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Conventions  
The following conventions are used in this manual:  
<>  
Angle brackets that contain numbers separated by an ellipsis represent a  
range of values associated with a bit or signal name—for example,  
P0.<3..0>.  
»
The » symbol leads you through nested menu items and dialog box options  
to a final action. The sequence File»Page Setup»Options directs you to  
pull down the File menu, select the Page Setup item, and select Options  
from the last dialog box.  
This icon denotes a note, which alerts you to important information.  
This icon denotes a caution, which advises you of precautions to take to  
avoid injury, data loss, or a system crash. When this symbol is marked on  
the product, refer to the Read Me First: Safety and Radio-Frequency  
Interference document, shipped with the product, for precautions to take.  
When symbol is marked on a product it denotes a warning advising you to  
take precautions to avoid electrical shock.  
When symbol is marked on a product it denotes a component that may be  
hot. Touching this component may result in bodily injury.  
bold  
Bold text denotes items that you must select or click in the software, such  
as menu items and dialog box options. Bold text also denotes parameter  
names.  
italic  
Italic text denotes variables, emphasis, a cross-reference, hardware labels,  
or an introduction to a key concept. Italic text also denotes text that is a  
placeholder for a word or value that you must supply.  
monospace  
Text in this font denotes text or characters that you should enter from the  
keyboard, sections of code, programming examples, and syntax examples.  
This font is also used for the proper names of disk drives, paths, directories,  
programs, subprograms, subroutines, device names, functions, operations,  
variables, filenames, and extensions.  
 
 
Chapter 1  
National Instruments Documentation ............................................................................1-2  
Installing Application Software, NI-DAQ, and the E/M Series DAQ Device ..............1-4  
Installing the Terminal Block..........................................................................1-4  
Chapter 2  
Analog Input Signal Connections..................................................................................2-1  
Ground-Referencing the Signals .....................................................................2-2  
3-Wire Resistive Sensor Configuration...........................................................2-5  
Lead-Resistance Compensation Using a 3-Wire Resistive Sensor  
Front Connector .............................................................................................................2-7  
Chapter 3  
Auto-Zero..........................................................................................3-2  
Configurable Settings in MAX......................................................................................3-2  
NI-DAQmx......................................................................................................3-3  
Creating a Global Channel or Task...................................................3-3  
Verifying the Signal.......................................................................................................3-4  
Verifying the Signal in NI-DAQmx Using a Task or Global Channel ...........3-4  
© National Instruments Corporation  
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SCXI-1503 User Manual  
 
Contents  
Chapter 4  
RTDs ............................................................................................................... 4-5  
RTD Measurement Errors ................................................................ 4-6  
Thermistors ..................................................................................................... 4-10  
Chapter 5  
Specifying Channel Strings in NI-DAQmx .................................................... 5-11  
Text Based ADEs ............................................................................. 5-11  
Programmable NI-DAQmx Properties ............................................. 5-13  
Calibration..................................................................................................................... 5-13  
Internal/Self-Calibration ................................................................................. 5-13  
External Calibration ........................................................................................ 5-13  
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Contents  
Appendix A  
Specifications  
Appendix B  
Common Questions  
Glossary  
Index  
Figures  
Figure 2-3.  
3-Wire Resistive Sensor Configuration.................................................2-5  
Figure 4-1.  
Figure 4-3.  
Block Diagram of SCXI-1503...............................................................4-2  
Resistance-Temperature Curve for a 100 Ω Platinum RTD,  
Resistance-Temperature Curve for a 2,252 Ω Thermistor....................4-11  
Figure 4-4.  
Figure 5-1.  
Typical Program Flowchart for Voltage Measurement Channels.........5-2  
Figure A-1. SCXI-1503 Dimensions ........................................................................A-5  
Figure B-1. Removing the SCXI-1503.....................................................................B-2  
© National Instruments Corporation  
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Contents  
Tables  
Table 1-1.  
Supported SCXI-1503 Terminal Blocks............................................... 1-4  
Table 2-1.  
Front Signal Pin Assignments .............................................................. 2-8  
Table 5-2.  
Table 5-3.  
Table 5-4.  
Table 5-5.  
NI-DAQmx RTD Measurement Properties ......................................... 5-5  
NI-DAQmx Thermistor Measurement Properties ............................... 5-6  
NI-DAQmx Thermocouple Measurement Properties .......................... 5-7  
Programming a Task in LabVIEW ...................................................... 5-8  
Table A-1.  
RTD Measurement Accuracy ............................................................... A-2  
SCXI-1503 User Manual  
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1
About the SCXI-1503  
This manual describes the electrical and mechanical aspects of the  
SCXI-1503 module and contains information concerning its installation  
and operation. The SCXI-1503 module provides 16 differential input  
channels and 16 channels of 100 μA current excitation and one cold  
junction sensor channel. The SCXI-1503 is ideally suited for measuring  
resistive transducers, such as RTDs or thermistors.  
Each channel has an amplifier with a selectable gain of 1 or 100 and a  
lowpass filter with a 5 Hz cutoff frequency to reject 50/60 Hz noise.  
The SCXI-1503 can programmatically connect each input to ground, which  
greatly improves its accuracy by enabling a self-calibration of each input to  
reduce offset drift errors.  
You can multiplex several SCXI-1503 modules and other SCXI modules  
into a single channel on the DAQ device, greatly increasing the number of  
analog input signals that you can digitize.  
Detailed specifications of the SCXI-1503 modules are listed in  
Appendix A, Specifications.  
What You Need to Get Started  
To set up and use the SCXI-1503, you need the following items:  
Hardware  
SCXI-1503 module  
One of the following terminal blocks:  
SCXI-1306—front-mount terminal block with screw  
terminal connectivity.  
SCXI-1310—custom kit for custom connectivity.  
TBX-96—DIN EN mount terminal block with screw terminal  
connectivity.  
SCXI or PXI/SCXI combo chassis  
© National Instruments Corporation  
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SCXI-1503 User Manual  
 
   
Chapter 1  
About the SCXI-1503  
One of the following:  
SCXI-1600  
E/M Series DAQ device  
Computer  
Cabling, cable adapter, and sensors as required for your  
application  
Software  
NI-DAQ 8.1 or later  
Application software, such as LabVIEW, LabWindows/CVI,  
Measurement Studio, or other programming environments  
Documentation  
Read Me First: Safety and Radio-Frequency Interference  
DAQ Getting Started Guide  
SCXI Quick Start Guide  
SCXI-1503 User Manual  
Terminal block installation guide  
Documentation for your software  
Tools  
Wire cutter  
Wire stripper  
Phillips screwdriver  
National Instruments Documentation  
The SCXI-1503 User Manual is one piece of the documentation set for data  
acquisition (DAQ) systems. You could have any of several types of  
manuals depending on the hardware and software in the system. Use the  
manuals you have as follows:  
The SCXI Quick Start Guide—This document contains a quick  
overview for setting up an SCXI chassis, installing SCXI modules and  
terminal blocks, and attaching sensors. It also describes setting up the  
SCXI system in MAX.  
SCXI-1503 User Manual  
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Chapter 1  
About the SCXI-1503  
SCXI or PXI/SCXI chassis manual—Read this manual for  
maintenance information on the chassis and for installation  
instructions.  
The DAQ Getting Started Guide—This document has information on  
installing NI-DAQ and the E/M Series DAQ device. Install these  
before you install the SCXI module.  
The SCXI hardware user manuals—Read these manuals for detailed  
information about signal connections and module configuration. They  
also explain, in greater detail, how the module works and contain  
application hints.  
Accessory installation guides or manuals—Read the terminal block  
and cable assembly installation guides. They explain how to physically  
connect the relevant pieces of the system. Consult these guides when  
you are making the connections.  
The E/M Series DAQ device documentation—This documentation has  
detailed information about the DAQ device that plugs into or is  
connected to the computer. Use this documentation for hardware  
installation and configuration instructions, specification information  
about the DAQ device, and application hints.  
Software documentation—You may have both application software  
and NI-DAQ software documentation. National Instruments (NI)  
application software includes LabVIEW, LabWindows/CVI, and  
Measurement Studio. After you set up the hardware system, use either  
your application software documentation or the NI-DAQ  
documentation to help you write your application. If you have a large,  
complex system, it is worthwhile to look through the software  
documentation before you configure the hardware.  
One or more of the following help files for software information:  
Start»Programs»National Instruments»NI-DAQ»  
NI-DAQmx Help  
Start»Programs»National Instruments»NI-DAQ»  
Traditional NI-DAQ User Manual  
Start»Programs»National Instruments»NI-DAQ»  
Traditional NI-DAQ Function Reference Help  
You can download NI documents from ni.com/manuals. To download  
the latest version of NI-DAQ, click Drivers and Updates at ni.com.  
© National Instruments Corporation  
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Chapter 1  
About the SCXI-1503  
Installing Application Software, NI-DAQ, and the  
E/M Series DAQ Device  
Refer to the DAQ Getting Started Guide packaged with the NI-DAQ  
software to install your application software, NI-DAQ driver software, and  
the DAQ device to which you will connect the SCXI-1503. NI-DAQ 8.1 or  
later is required to configure and program the SCXI-1503 module. If you  
do not have NI-DAQ 8.1 or later, you can either contact an NI sales  
representative to request it on a CD or download the latest NI-DAQ version  
from ni.com.  
Note Refer to the Read Me First: Radio-Frequency Interference document before  
removing equipment covers or connecting or disconnecting any signal wires.  
Installing the SCXI-1503 Module into the SCXI Chassis  
Refer to the SCXI Quick Start Guide to install your SCXI-1503 module.  
Installing the Terminal Block  
Table 1-1 shows the supported SCXI-1503 terminal blocks. Refer to the  
SCXI Quick Start Guide and the terminal block installation guide for more  
information about the terminal block.  
Table 1-1. Supported SCXI-1503 Terminal Blocks  
Terminal Block  
CJC Sensor  
Measurement Type  
SCXI-1306  
Yes  
Resistive temperature  
measurements  
TBX-96  
No  
No  
Custom signals  
SCXI-1310  
Configuring the SCXI System Software  
Refer to the SCXI Quick Start Guide and the user manuals of the modules  
in your application to configure and verify them in software.  
SCXI-1503 User Manual  
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Chapter 1  
About the SCXI-1503  
Verifying the SCXI-1503 Installation  
Refer to the SCXI Quick Start Guide, for details about testing the SCXI  
chassis and module installation in software. Refer to Chapter 3,  
Configuring and Testing, for details about setting up a task and verifying  
the input signal.  
© National Instruments Corporation  
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SCXI-1503 User Manual  
 
 
2
Connecting Signals  
This chapter describes the input and output signal connections to the  
SCXI-1503 module with the module front connector and rear signal  
connector. This chapter also includes connection instructions for the  
signals on the SCXI-1503 module when using the SCXI-1306 terminal  
block.  
In addition to this section, refer to the installation guide of the terminal  
block for detailed information regarding connecting the signals. If you are  
using a custom cable or connector block, refer to the Front Connector  
section.  
Analog Input Signal Connections  
Each differential input (AI+ and AI–) goes to a separate filter and amplifier  
that is multiplexed to the module output buffer. If the terminal block has a  
temperature sensor, the sensor output—connected to pins A3 and/or A4  
(CJ SENSOR)—is also filtered and multiplexed to the module output  
buffer.  
The differential input signal range of an SCXI-1503 module input channel  
is 10 V when using a gain of 1 or 0.1 V when using a gain of 100. This  
differential input range is the maximum measurable voltage difference  
between the positive and negative channel inputs. The common-mode input  
signal range of an SCXI-1503 module input channel is 10 V. This  
common-mode input range for either positive or negative channel input is  
the maximum input voltage that results in a valid measurement. Each  
channel includes input protection circuitry to withstand the accidental  
application of voltages up to 42 VDC powered on or 25 VDC  
powered off.  
Caution Exceeding the input damage level ( 42 VDC powered on or 25 VDC powered  
off between input channels and chassis ground) can damage the SCXI-1503 module, the  
SCXIbus, and the DAQ device. NI is not liable for any injuries resulting from such signal  
connections.  
© National Instruments Corporation  
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Chapter 2  
Connecting Signals  
Note Exceeding the differential or common-mode input channel ranges results in a  
distorted signal measurement, and can also increase the settling time requirement of the  
connected E/M Series DAQ device.  
Ground-Referencing the Signals  
Do not ground signals that are already ground-referenced; doing so results  
in a ground loop, which can adversely affect the measurement accuracy.  
Directly grounding floating signals to the chassis ground without using a  
bias resistor is not recommended as this can result in noisy readings  
Connecting Resistive Devices to the SCXI-1503  
You can connect resistive devices to the SCXI signal conditioning system  
in a 4-, 2-, or 3-wire configuration. Figures 2-1 through 2-4 illustrate  
various ways to connect sensors for current excitation and voltage  
measurements using the SCXI-1503 with the SCXI-1306 terminal block.  
Refer to the appropriate ADE and SCXI documentation for information  
concerning setting appropriate voltage gains for the analog inputs.  
You can use the SCXI-1306 terminal block to make signal connections to  
the SCXI-1503. When using the SCXI-1306 terminal block, refer to the  
SCXI-1306 Terminal Block Installation Guide.  
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Chapter 2  
Connecting Signals  
4-Wire Configuration  
The 4-wire configuration, also referred to as a Kelvin connection, is shown  
in Figure 2-1. The 4-wire configuration uses one pair of wires to deliver the  
excitation current to the resistive sensor and uses a separate pair of wires to  
sense the voltage across the resistive sensor. Because of the high input  
impedance of the differential amplifier, negligible current flows through  
the sense wires. This results in a very small lead-resistance voltage drop  
error. The main disadvantage of the 4-wire connection is the greater  
number of field wires required.  
External Sensor  
RL1  
SCXI-1306  
SCXI-1503  
Channel X  
RL2  
IEX+  
AI+  
+
I = 100 µA  
RT  
AI–  
RL4  
RL3  
IEX–  
CH X  
ON  
Figure 2-1. 4-Wire Resistive Sensor Connected in a 4-Wire Configuration  
© National Instruments Corporation  
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SCXI-1503 User Manual  
 
     
Chapter 2  
Connecting Signals  
2-Wire Configuration  
The basic 2-wire configuration is shown in Figure 2-2. In this configuration  
an error voltage (VE) is introduced into the measurement equal to the  
excitation current (IEX) times the sum of the two lead resistances, RL1 and  
RL2. If we assume equal lead resistances, RL1 = RL2 = RL, the magnitude of  
the error voltage is:  
VE = 2RLIEX  
This is the most commonly used configuration for connecting thermistors  
to a signal conditioning system because the large sensitivity of thermistors  
usually results in the introduction of a negligible error by the lead  
resistances.  
RTDs typically have a much smaller sensitivity and nominal resistance than  
thermistors, therefore a 2-wire configuration usually results in the  
introduction of larger errors by the lead resistance.  
External Sensor  
RL1  
SCXI-1306  
SCXI-1503  
Channel X  
IEX+  
AI+  
+
I = 100 µA  
RT  
AI–  
RL2  
IEX–  
CH X  
ON  
Figure 2-2. 2-Wire Resistive Sensor Connected in a 2-Wire Configuration  
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Chapter 2  
Connecting Signals  
3-Wire Resistive Sensor Configuration  
If you are using a 3-wire resistive sensor, you can reduce the error voltage  
by one-half over the 2-wire measurement by connecting the device as  
shown in Figure 2-3. In this configuration, very little current flows through  
RL3 and therefore RL2 is the only lead resistance that introduces an error into  
the measurement. The resulting measurement error is:  
VE = RL2IEX  
External Sensor  
RL1  
SCXI-1306  
SCXI-1503  
Channel X  
IEX+  
AI+  
RL3  
+
RT  
I = 100 µA  
AI–  
RL2  
IEX–  
CH X  
ON  
Figure 2-3. 3-Wire Resistive Sensor Configuration  
© National Instruments Corporation  
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SCXI-1503 User Manual  
 
     
Chapter 2  
Connecting Signals  
Lead-Resistance Compensation Using a 3-Wire Resistive Sensor and  
Two Matched Current Sources  
You can compensate for the errors introduced by lead-resistance voltage  
drops by using a 3-wire resistive sensor and two matched current sources  
connected as shown in Figure 2-4.  
External Sensor  
RL1  
SCXI-1306  
SCXI-1503  
EX0+  
AI0+  
AI0–  
+
I = 100 µA  
EX0–  
RT  
ON  
RL2  
RL3  
EX1+  
AI1+  
AI1–  
+
I = 100 µA  
EX1–  
ON  
Figure 2-4. 3-Wire Configuration Using Matched Current Sources  
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Chapter 2  
Connecting Signals  
In this configuration, the lead-resistance voltage drop across RL3 is  
converted into a common-mode voltage that is rejected by the differential  
amplifier. Also, the polarity of the lead-resistance voltage drops across RL1  
and RL2 are series opposing, relative to the inputs of the differential  
amplifier, eliminating their effect on the voltage measured across RT.  
Note RL1 and RL2 are assumed to be equal.  
The effectiveness of this method depends on the matching of the current  
sources. Each current source on the SCXI-1503 has an accuracy of 0.05%.  
This accuracy results in a worst-case matching of 0.1%. Refer to the  
Chapter 4, Theory of Operation, for accuracy considerations of RTDs and  
thermistors.  
Front Connector  
The pin assignments for the SCXI-1503 front signal connector are shown  
in Table 2-1.  
Note Do not make any connections to RSVD pins.  
© National Instruments Corporation  
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SCXI-1503 User Manual  
 
 
Chapter 2  
Connecting Signals  
Table 2-1. Front Signal Pin Assignments  
Front Connector Diagram  
Pin Number  
Column A  
GND  
GND  
GND  
GND  
RSVD  
RSVD  
RSVD  
RSVD  
NC  
Column B  
AI0–  
Column C  
AI0+  
32  
31  
30  
29  
28  
27  
26  
25  
24  
23  
22  
21  
20  
19  
18  
17  
16  
15  
14  
13  
12  
11  
10  
9
Column  
AI1–  
AI1+  
A
B
C
AI2–  
AI2+  
32  
31  
30  
29  
28  
27  
26  
25  
24  
23  
22  
21  
20  
19  
18  
17  
16  
15  
14  
13  
12  
11  
10  
9
AI3–  
AI3+  
AI4–  
AI4+  
AI5–  
AI5+  
AI6–  
AI6+  
AI7–  
AI7+  
IEX0–  
IEX1–  
IEX2–  
IEX3–  
IEX4–  
IEX5  
IEX0+  
IEX1+  
IEX2+  
IEX3+  
IEX4+  
IEX5+  
IEX6+  
IEX7+  
AI8+  
NC  
NC  
NC  
RSVD  
RSVD  
NC  
IEX6–  
IEX7–  
AI8–  
NC  
GND  
GND  
GND  
GND  
NC  
AI9–  
AI9+  
AI10–  
AI11–  
AI12–  
AI13–  
AI14–  
AI15–  
IEX8–  
IEX9–  
IEX10–  
IEX11–  
IEX12–  
IEX13–  
IEX14–  
IEX15–  
AI10+  
AI11+  
AI12+  
AI13+  
AI14+  
AI15+  
IEX8+  
IEX9+  
IEX10+  
IEX11+  
IEX12+  
IEX13+  
IEX14+  
IEX15+  
NC  
NC  
8
NC  
7
8
NC  
6
5
7
NC  
4
6
NC  
3
5
NC  
2
4
CJ SENSOR  
CJ SENSOR  
CGND  
+5 V  
1
3
NC—no connection  
RSVD—reserved  
2
1
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Table 2-2. Signal Descriptions  
Pin  
Signal Name  
+5 V  
Description  
A1  
+5 VDC Source—Used to power circuitry on the  
terminal block. 0.1 mA of source not protected.  
A13 – A16,  
A29 – A32  
GND  
Ground—Tied to the SCXI module ground.  
A1, A19, A20,  
A25 – A28  
RSVD  
C GND  
Reserved—This pin is reserved. Do not connect  
any signal to this pin.  
A2  
Chassis Ground—Connects to the SCXI chassis.  
B24 – B17,  
B8 – B1  
IEX<0..7> –,  
IEX<8..15> –  
Negative Excitation—Connects to the channel  
ground reference. This is the return path for the  
corresponding IEX+ channel.  
C24 – C17,  
C8 – C1  
IEX<0..7> +,  
IEX<8..15> +  
Positive Excitation—Connects to the positive  
current output of the channel.  
A3, A4  
CJ SENSOR  
Cold-Junction Temperature Sensor  
Input—Connects to the temperature sensor of  
the terminal block.  
B30 – B 25,  
B16 – B9  
AI <0..7> –,  
AI <8..15> –  
Negative Input Channels—Negative side of  
differential input channels.  
C32 – C25,  
C16 – C9  
AI <0..7> +,  
AI <8..15> +  
Positive Input Channels—Positive side of  
differential input channels.  
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Connecting Signals  
Rear Signal Connector  
Table 2-3 shows the SCXI-1503 module rear signal connector pin  
assignments.  
Table 2-3. Rear Signal Pin Assignments  
Rear Connector Diagram  
Signal Name  
AI GND  
AI 0 +  
NC  
Pin Number  
Pin Number  
Signal Name  
1
2
AI GND  
3
4
AI 0 –  
5
6
NC  
1
3
5
7
9
2
4
NC  
7
8
NC  
NC  
9
10  
12  
14  
16  
18  
20  
22  
24  
26  
28  
30  
32  
34  
36  
38  
40  
42  
44  
46  
48  
50  
NC  
6
8
NC  
11  
13  
15  
17  
19  
21  
23  
25  
27  
29  
31  
33  
35  
37  
39  
41  
43  
45  
47  
49  
NC  
10  
NC  
NC  
11 12  
13 14  
15 16  
17 18  
19 20  
21 22  
23 24  
25 26  
27 28  
29 30  
31 32  
33 34  
35 36  
37 38  
39 40  
41 42  
43 44  
45 46  
47 48  
49 50  
NC  
NC  
NC  
NC  
NC  
NC  
NC  
NC  
NC  
DIG GND  
SER DAT IN  
DAQ D*/A  
SLOT 0 SEL*  
NC  
SER DAT OUT  
NC  
NC  
NC  
DIG GND  
NC  
NC  
SCAN CLK  
NC  
SER CLK  
NC  
NC  
NC  
NC  
RSVD  
NC  
NC  
RSVD  
NC  
NC means no connection.  
RSVD means reserved.  
NC  
NC  
NC  
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Chapter 2  
Connecting Signals  
Rear Signal Connector Descriptions  
The rear signal connector on the cabled module is the interface between  
the DAQ device and all modules in the SCXI chassis. AI 0 is used to  
differentially multiplex all 16 channels, the CJ sensor, and analog signals  
from the modules to the connected DAQ device.  
The communication signals between the DAQ device and the SCXI system  
are listed in Table 2-4. If the DAQ device is connected to the SCXI-1503,  
these digital lines are unavailable for general-purpose digital I/O.  
Table 2-4. SCXI-1503 50-Pin Rear Connector Signals  
NI-DAQmx  
SCXI  
Device Signal  
Pin  
Signal Name  
Name  
Direction  
Description  
1, 2  
AI GND  
AI GND  
Analog input ground—connects to  
the analog input ground of the DAQ  
device.  
3
4
AI 0 +  
AI 0 +  
AI 0 –  
D GND  
P0.0  
Input  
Input  
Channel 0 positive—used to  
differentially multiplex all  
16 channels, the CJ sensor, and  
analog signals from the modules to  
the connected DAQ device.  
AI 0 –  
Channel 0 negative—used to  
differentially multiplex all  
16 channels, the CJ sensor, and  
analog signals from the modules to  
the connected DAQ device.  
24, 33  
DIG GND  
SER DAT IN  
Digital ground—these pins supply  
the reference for E/M Series DAQ  
device digital signals and are  
connected to the module digital  
ground.  
25  
Input  
Serial data in—this signal taps into  
the SCXIbus MOSI line to send  
serial input data to a module or  
Slot 0.  
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Chapter 2  
Connecting Signals  
Table 2-4. SCXI-1503 50-Pin Rear Connector Signals (Continued)  
NI-DAQmx  
Device Signal  
Name  
SCXI  
Signal Name  
Pin  
Direction  
Description  
26  
SER DAT OU  
T
P0.4  
Output  
Serial data out—this signal taps  
into the SCXIbus MISO line to  
accept serial output data from a  
module.  
27  
DAQ D*/A  
P0.1  
Input  
Board data/address line—this  
signal taps into the SCXIbus D*/A  
line to indicate to the module  
whether the incoming serial stream  
is data or address information.  
29  
36  
SLOT 0 SEL*  
SCAN CLK  
P0.2  
Input  
Input  
Slot 0 select—this signal taps into  
the SCXIbus INTR* line to indicate  
whether the information on MOSI  
is being sent to a module or Slot 0.  
AI HOLD COMP,  
AI HOLD  
Scan clock—a rising edge indicates  
to the scanned SCXI module that  
the E/M Series DAQ device has  
taken a sample and causes the  
module to advance channels.  
37  
SER CLK  
RSVD  
EXTSTROBE*  
RSVD  
Input  
Input  
Serial clock—this signal taps into  
the SCXIbus SPICLK line to clock  
the data on the MOSI and MISO  
lines.  
43, 46  
Reserved.  
Note: All other pins are not connected.  
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Configuring and Testing  
This chapter discusses configuring the SCXI-1503 in MAX using  
NI-DAQmx, creating and testing a virtual channel, global channel,  
and/or task.  
Notes You must have NI-DAQmx 8.1 or later installed.  
Refer to the SCXI Quick Start Guide if you have not already configured the chassis.  
SCXI-1503 Software-Configurable Settings  
This section describes how to set the gain/input signal range and how to  
configure your software for compatible sensor types. It also describes how  
to perform configuration of these settings for the SCXI-1503 in  
NI-DAQmx. For more information on the relationship between the settings  
and the measurements and how to configure settings in your application,  
refer to Chapter 4, Theory of Operation.  
Common Software-Configurable Settings  
This section describes the most frequently used software-configurable  
settings for the SCXI-1503. Refer to Chapter 5, Using the SCXI-1503,  
for a complete list of software-configurable settings.  
Gain/input range is a software-configurable setting that allows you to  
choose the appropriate amplification to fully utilize the range of the  
E/M Series DAQ device. In most applications NI-DAQ chooses and sets  
the gain for you determined by the input range. This feature is described in  
Chapter 5, Using the SCXI-1503. Otherwise, you should determine the  
appropriate gain using the input signal voltage range and the full-scale  
limits of the SCXI-1503 output. You can select a gain of 1 or 100 on a per  
channel basis.  
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Chapter 3  
Configuring and Testing  
The front end of the SCXI-1503 includes a software configurable switch  
that allows you to programmatically connect the input channels of the  
SCXI-1503 to either the front connector or internal ground. When using  
autozero, the coupling mode is set automatically. Refer to Table 5-1,  
NI-DAQmx Voltage Measurement Properties, for details about the  
available input coupling modes supported by the SCXI-1503.  
CJC Source/Value  
When using a terminal block that has a CJ sensor for thermocouple  
measurements, you can set the CJC source as internal, which scans the  
sensor at the beginning of each measurement and scales the readings  
accordingly.  
Auto-Zero  
Setting the Auto-zero mode to Once improves the accuracy of the  
measurement. With auto-zero enabled, the inputs of the SCXI-1503 are  
internally grounded. The driver makes a measurement when the task begins  
and then subtracts the measured offset from all future measurements.  
Configurable Settings in MAX  
Note If you are not using an NI ADE or are using an unlicensed copy of an NI ADE,  
additional dialog boxes from the NI License Manager appear allowing you to create a task  
or global channel in unlicensed mode. These messages continue to appear until you install  
version 8.1 or later of an NI ADE.  
This section describes where you can access each software-configurable  
setting in MAX. The location of the settings varies depending on the  
version of NI-DAQmx you use. Refer to the DAQ Getting Started Guide  
and the SCXI Quick Start Guide for more information on installing and  
configuring the hardware. You can use DAQ Assistant to graphically  
configure common measurement tasks, channels, or scales.  
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Chapter 3  
Configuring and Testing  
NI-DAQmx  
Using NI-DAQmx, you can configure software settings such as sensor type  
and gain/input signal range in the following ways:  
Task or global channel in MAX  
Functions in your application  
Note All software-configurable settings are not configurable both ways. This section only  
discusses settings in MAX. Refer to Chapter 5, Using the SCXI-1503, for information on  
using functions in your application.  
Dependent upon the terminal block configuration use, you can use the  
SCXI-1503 module to make the following types of measurements:  
Voltage input  
Thermocouple  
RTD  
Thermistors  
Creating a Global Channel or Task  
To create a new voltage, temperature, or current input NI-DAQmx global  
task or channel, complete the following steps:  
1. Double-click Measurement & Automation on the desktop.  
2. Right-click Data Neighborhood and select Create New.  
3. Select NI-DAQmx Task or NI-DAQmx Global Channel, and click  
Next.  
4. Select Analog Input.  
5. Select one of the following:  
Voltage  
Temperature and then select one of the following:  
Iex Thermistor  
RTD  
Thermocouple  
Vex Thermistor  
6. If you are creating a task, you can select a range of channels by holding  
down the <Shift> key while selecting the channels. You can select  
multiple individual channels by holding down the <Ctrl> key while  
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Configuring and Testing  
selecting channels. If you are creating a channel, you can only select  
one channel. Click Next.  
7. Name the task or channel and click Finish.  
8. Select the channel(s) you want to configure. You can select a range of  
channels by holding down the <Shift> key while selecting the  
channels. You can select multiple individual channels by holding down  
the <Ctrl> key while selecting channels.  
Note If you want to add channels of various measurement types to the same task, click  
the Add Channels button to select the measurement type for the additional channels.  
9. Enter the specific values for your application in the Settings tab.  
Context help information for each setting is provided on the right  
side of the screen. Configure the input signal range using either  
NI-DAQmx Task or NI-DAQmx Global Channel. When you set the  
minimum and maximum range of NI-DAQmx Task or NI-DAQmx  
Global Channel, the driver selects the best gain for the measurement.  
You also can set it through your application.  
10. If you are creating a task and want to set timing or triggering controls,  
enter the values in the Task Timing and Task Triggering tabs.  
11. Click Device and select Auto Zero mode if desired.  
Verifying the Signal  
This section describes how to take measurements using test panels in order  
to verify signal, and configuring and installing a system in NI-DAQmx.  
Verifying the Signal in NI-DAQmx Using a Task or Global Channel  
You can verify the signals on the SCXI-1503 using NI-DAQmx by  
completing the following steps:  
1. Expand Data Neighborhood.  
2. Expand NI-DAQmx Tasks.  
3. Click the task you created in the Creating a Global Channel or Task  
section.  
4. Select the channel(s) you want to verify. You can select a block of  
channels by holding down the <Shift> key or multiple channels by  
holding down the <Ctrl> key. Click OK.  
5. Enter the appropriate information on the Settings and Device tab.  
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Configuring and Testing  
6. Click the Test button.  
7. Click the Start button.  
8. After you have completed verifying the channels, click the Stop  
You have now verified the SCXI-1503 configuration and signal connection.  
Note For more information on how to further configure the SCXI-1503, or how to use  
LabVIEW to configure the module and take measurements, refer to Chapter 5, Using the  
SCXI-1503.  
© National Instruments Corporation  
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Theory of Operation  
This chapter provides a brief overview and a detailed discussion of the  
circuit features of the SCXI-1503 module. Refer to Figure 4-1 while  
reading this section.  
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Chapter 4  
Theory of Operation  
Rear Signal Connector  
SCXIbus Connector  
Mux  
32-to-1 Mux  
Gain 0  
Gain 31  
Front Signal Connector  
Figure 4-1. Block Diagram of SCXI-1503  
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Chapter 4  
Theory of Operation  
The major components of the SCXI-1503 modules are as follows:  
Rear signal connector  
SCXIbus connector  
SCXIbus interface  
Digital control circuitry  
Analog circuitry  
The SCXI-1503 modules consist of 16 multiplexed input channels, each  
with a software-programmable gain of 1 or 100. Each input channel has its  
own lowpass filter. Each channel has a fixed 100 μA current excitation. The  
SCXI-1503 modules also have a digital section for automatic control of  
channel scanning, temperature sensor selection, gain selection, and  
auto-zero mode.  
Rear Signal Connector, SCXIbus Connector, and  
SCXIbus Interface  
The SCXIbus controls the SCXI-1503 module. The SCXIbus interface  
connects the rear signal connector to the SCXIbus, allowing a DAQ device  
to control the SCXI-1503 module and the rest of the chassis.  
Digital Control Circuitry  
The digital control circuitry consists of the Address Handler and registers  
that are necessary for identifying the module, reading/setting calibration  
information, setting the gain, and selecting the appropriate channel.  
Analog Circuitry  
The analog circuitry per channel consists of a fixed lowpass filter and an  
amplifier with a software selectable gain of 1 or 100. The CJ SENSOR  
channel has a lowpass filter buffered by a unity gain amplifier. The  
channels and CJ SENSOR are multiplexed to a single output buffer.  
Analog Input Channels  
Each of the 16 differential analog input channels feeds to a separate  
instrumentation amplifier with a programmable gain of 1 or 100. Each  
channel has a fixed 100 μA current excitation. Then the signal passes  
through a fixed 2-pole, 5 Hz lowpass filter.  
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Chapter 4  
Theory of Operation  
The CJ SENSOR input channel is used to read the sensor temperature from  
the terminal block. The temperature sensor is for cold-junction  
compensation of thermocouple measurements. The CJ SENSOR channel  
also passes through a 5 Hz lowpass filter to reject unwanted noise on the  
SCXI-1503. Along with the other 16 input channels, the CJ SENSOR is  
multiplexed to the output buffer, where it can be read by the DAQ device.  
Operation of the Current Sources  
The current sources on the SCXI-1503 continuously provide 16 channels  
of 100 μA current excitation. These current sources are on whenever the  
SCXI chassis is powered-on. The current sources on the SCXI-1503 are  
designed to be accurate to within 0.05% of the specified value with a  
temperature drift of no more than 5 ppm/°C. The high accuracy and  
stability of these current sources makes them especially well suited to  
measuring resistance to a high degree of accuracy.  
Theory of Multiplexed Operation  
In multiplexed mode, all input channels of an SCXI module are  
multiplexed into a single analog input channel of the DAQ device.  
Multiplexed mode operation is ideal for high channel count systems.  
Multiplexed mode is typically used for performing scanning operations  
with the SCXI-1503. The power of SCXI multiplexed mode scanning is its  
ability to route many input channels to a single channel of the DAQ device.  
The multiplexing operation of the analog input signals is performed  
entirely by multiplexers in the SCXI modules, not inside the DAQ device  
or SCXI chassis. In multiplexed mode the SCXI-1503 scanned channels are  
kept by the NI-DAQ driver in a scan list. Immediately prior to a multiplexed  
scanning operation, the SCXI chassis is programmed with a module scan  
list that controls which module sends its output to the SCXIbus during a  
scan through the cabled SCXI module.  
The list can contain channels in any physical order and the multiplexer can  
sequence the channel selection from the scan list in any order. The ordering  
of scanned channels need not be sequential. Channels can occur multiple  
times in a single scan list. The scan list can contain an arbitrary number of  
channels for each module entry in the scan list, limited to a total of  
512 channels per DAQ device. This is referred to as flexible scanning  
(random scanning). Not all SCXI modules provide flexible scanning.  
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Theory of Operation  
The module includes first-in first-out (FIFO) memory for storing the  
channel scan list defined in your application code. NI-DAQ drivers load the  
FIFO based on the channel assignments you make in your application. You  
need not explicitly program the module FIFO as this is done automatically  
for you by the NI-DAQ driver.  
When you configure a module for multiplexed mode operation, the routing  
of multiplexed signals to the DAQ device depends on which module in the  
SCXI system is cabled to the DAQ device. There are several possible  
scenarios for routing signals from the multiplexed modules to the DAQ  
device.  
If the scanned SCXI-1503 module is not directly cabled to the DAQ device,  
the module sends its signals through the SCXIbus to the cabled module.  
The cabled module, whose routing is controlled by the SCXI chassis, routes  
the SCXIbus signals to the DAQ device through the AI 0 pin on its rear  
signal connector.  
If the DAQ device scans the cabled module, the module routes its input  
signals through the AI 0 pin on its rear signal connector to a single channel  
on the DAQ device.  
Measuring Temperature with Resistive Transducers  
This section discusses RTDs and thermistors, and describes accuracy  
considerations when connecting resistive transducers to the signal  
conditioning system.  
RTDs  
A resistive-temperature detector (RTD) is a temperature-sensing device  
whose resistance increases with temperature. An RTD consists of a wire  
coil or deposited film of pure metal. RTDs are made of different metals and  
have different resistances, but the most popular RTD is made of platinum  
and has a nominal resistance of 100 Ω at 0 °C.  
RTDs are known for their excellent accuracy over a wide temperature  
range. Some RTDs have accuracies as high as 0.01 Ω (0.026 °C) at 0 °C.  
RTDs are also extremely stable devices. Common industrial RTDs drift less  
than 0.1 °C/year, and some models are stable to within 0.0025 °C/year.  
RTDs are sometimes difficult to measure because they have relatively low  
nominal resistance (commonly 100 Ω) that changes only slightly with  
temperature (less than 0.4 Ω/°C). To accurately measure these small  
© National Instruments Corporation  
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Chapter 4  
Theory of Operation  
changes in resistance, you must use special configurations that minimize  
measured errors caused by lead-wire resistance.  
RTD Measurement Errors  
Because the RTD is a resistive device, you must pass a current through the  
device and monitor the resulting voltage. However, any resistance in the  
lead wires that connect the measurement system to the RTD adds error to  
the readings. For example, consider a 2-wire RTD element connected to a  
measurement system that also supplies a constant current, IEX, to excite the  
RTD. As shown in Figure 4-2, the voltage drop across the lead resistances  
(labeled RL) adds an error voltage to the measured voltage.  
IEX  
RL  
+
V0  
RT  
RL  
Figure 4-2. 2-Wire RTD Measurement  
For example, a lead resistance of 0.3 Ω in each wire adds a 0.6 Ω error to  
the resistance measurement. For a platinum RTD at 0 °C with α = 0.00385,  
the lead resistance equates to an error of approximately  
0.6 Ω  
---------------------------- = 1.6 °C  
0.385 Ω/°C  
Chapter 2, Connecting Signals, describes different ways of connecting  
resistive devices to the SCXI system.  
The Relationship Between Resistance and  
Temperature in RTDs  
Compared to other temperature-measurement devices, the output of an  
RTD is relatively linear with respect to temperature. The temperature  
coefficient, called alpha (α), differs between RTD curves. Although  
various manufacturers specify alpha differently, alpha is most commonly  
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Theory of Operation  
defined as the change in RTD resistance from 0 to 100 °C, divided by the  
resistance at 0 °C, divided by 100 °C:  
R100 R0  
α(Ω/Ω/°C) = -----------------------------  
R0 × 100 °C  
where  
R100 is the resistance of the RTD at 100 °C.  
R0 is the resistance of the RTD at 0 °C.  
For example, a 100 Ω platinum RTD with α = 0.003911 has a resistance of  
139.11 Ω at 100 °C.  
Figure 4-3 displays a typical resistance-temperature curve for a 100 Ω  
platinum RTD.  
480  
400  
320  
240  
160  
80  
0
80 160 240 320 400 480 560 640 720 800 880 960  
Figure 4-3. Resistance-Temperature Curve for a 100 Ω Platinum RTD, α = 0.00385  
© National Instruments Corporation  
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Chapter 4  
Theory of Operation  
Although the resistance-temperature curve is relatively linear, accurately  
converting measured resistance to temperature requires curve fitting. The  
following Callendar-Van Dusen equation is commonly used to approximate  
the RTD curve:  
RT = R0[1 + AT + BT2 + C(T 100)3]  
where  
RT is the resistance of the RTD at temperature T.  
R0 is the resistance of the RTD at 0 °C.  
A, B, and C are the Callendar-Van Dusen coefficients shown in  
Table 4-1.  
T is the temperature in °C.  
Table 4-1 lists the RTD types and their corresponding coefficients.  
Table 4-1. Platinum RTD Types  
Temperature  
Coefficient of  
Resistance  
(TCR, PPM)  
Typical  
R0  
Callendar-Van  
Dusen Coefficient  
Standard  
IEC-751  
DIN 43760  
BS 1904  
ASTM-E1137  
EN-60751  
3851  
100 Ω  
1000 Ω  
A = 3.9083 × 10–3  
B = –5.775 × 10–7  
C = –4.183 × 10–12  
Low cost  
vendor  
3750  
3916  
3920  
1000 Ω  
100 Ω  
100 Ω  
A = 3.81 × 10–3  
B = –6.02 × 10–7  
C = –6.0 × 10–12  
A = 3.9739 × 10–3  
B = –5.870 × 10–7  
C = –4.4 × 10–12  
A = 3.9787 × 10–3  
B = –5.8686 × 10–7  
C = –4.167 × 10–12  
compliant1  
JISC 1604  
US Industrial  
Standard D-100  
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Theory of Operation  
Table 4-1. Platinum RTD Types (Continued)  
Temperature  
Coefficient of  
Resistance  
(TCR, PPM)  
Typical  
R0  
Callendar-Van  
Standard  
Dusen Coefficient  
A = 3.9692 × 10–3  
B = –5.8495 × 10–7  
C = –4.233 × 10–12  
A = 3.9888 × 10–3  
B = –5.915 × 10–7  
C = –3.85 × 10–12  
US Industrial  
Standard  
American  
3911  
100 Ω  
ITS-90  
3928  
100 Ω  
1 No standard. Check TCR.  
For temperatures above 0 °C, coefficient C equals 0, reducing this equation  
to a quadratic. If you pass a known current, IEX, through the RTD and  
measure the output voltage developed across the RTD, V0, you can solve  
for T as follows:  
V0  
R0 -------  
IEX  
T = ------------------------------------------------------------------------------------------------  
V0  
2
2
–0.5 R A + R0 A 4R0B R0 -------  
0
IEX  
where  
V0 is the measured RTD voltage.  
IEX is the excitation current.  
© National Instruments Corporation  
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SCXI-1503 User Manual  
 
Chapter 4  
Theory of Operation  
Thermistors  
A thermistor is a piece of semiconductor made from metal oxides, pressed  
into a small bead, disk, wafer, or other shape, sintered at high temperatures,  
and finally coated with epoxy or glass. The resulting device exhibits an  
electrical resistance that varies with temperature.  
There are two types of thermistors: negative temperature coefficient (NTC)  
thermistors, whose resistance decreases with increasing temperature, and  
positive temperature coefficient (PTC) thermistors, whose resistance  
increases with increasing temperature. NTC thermistors are more  
commonly used than PTC thermistors, especially for temperature  
measurement applications.  
A main advantage of thermistors for temperature measurement is their  
extremely high sensitivity. For example, a 2,252 Ω thermistor has a  
sensitivity of –100 Ω/°C at room temperature. Higher resistance  
thermistors can exhibit temperature coefficients of –10 kΩ/°C or more.  
In comparison, a 100 Ω platinum RTD has a sensitivity of only 0.4 Ω/°C.  
Also, the physically small size and low thermal mass of a thermistor bead  
allows a very fast response to temperature changes.  
Another advantage of the thermistor is its relatively high resistance.  
Thermistors are available with base resistances (at 25 °C) ranging from  
hundreds to millions of ohms. This high resistance diminishes the effect of  
inherent resistances in the lead wires, which can cause significant errors  
with low resistance devices such as RTDs. For example, while RTD  
measurements typically require 3- or 4-wire connections to reduce errors  
caused by lead-wire resistances, 2-wire connections to thermistors are  
usually adequate.  
The major trade-off for the high resistance and sensitivity of the thermistor  
is its highly nonlinear output and relatively limited operating range.  
Depending on the type of thermistor, the upper range is typically limited to  
around 300 °C. Figure 4-4 shows the resistance-temperature curve for a  
2,252 Ω thermistor. The curve of a 100 Ω RTD is also shown for  
comparison.  
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,
Figure 4-4. Resistance-Temperature Curve for a 2,252 Ω Thermistor  
The thermistor has been used primarily for high-resolution measurements  
over limited temperature ranges. However, continuing improvements in  
thermistor stability, accuracy, and interchangeability have prompted  
increased use of thermistors in a variety of applications.  
Thermistor Measurement Circuits  
This section details information about thermistor measurement circuits.  
The most common technique is to use a current-source, and measure the  
voltage developed across the thermistor. Figure shows the measured  
voltage V0 equals RT × IEX.  
IEX  
+
RT  
V0  
Thermistor  
V0 = IEX x RT  
Figure 4-5. Thermistor Measurement with Constant Current Excitation  
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Theory of Operation  
The maximum resistance of the thermistor is determined from the current  
excitation value and the maximum voltage range of the input device. When  
using the SCXI-1503, the maximum measurable resistance is 100 kΩ.  
The level of the voltage output signal depends directly on the thermistor  
resistance and magnitude of the current excitation. Do not use a higher level  
of current excitation in order to produce a higher level output signal  
because the current causes the thermistor to heat internally, leading to  
temperature-measurement errors. This phenomena is called self-heating.  
When current passes through the thermistor, power dissipated by the  
thermistor equaling (IEX2RT), heats the thermistor.  
Thermistors, with their small size and high resistance, are particularly  
prone to these self-heating errors. Manufacturers typically specify this  
self-heating as a dissipation constant, which is the power required to heat  
the thermistor 1 °C from ambient temperature (mW/°C). The dissipation  
constant depends heavily on how easily heat is transferred away from the  
thermistor, so the dissipation constant can be specified for different  
media—in still air, water, or oil bath. Typical dissipation constants range  
anywhere from less than 0.5 mW/°C for still air to 10 mW/°C or higher for  
a thermistor immersed in water. A 2,252 Ω thermistor powered by a  
100 μA excitation current dissipates:  
I2R = 100 μA2 × 2,252 Ω = 0.0225 mW  
If this thermistor has a dissipation constant of 10 mW/°C, the thermistor  
self-heats 0.00225 °C so the self-heating from the 100 μA source of the  
SCXI-1503 is negligible for most applications. It is still important to  
carefully read self-heating specifications of the thermistors.  
Resistance/Temperature Characteristic of  
Thermistors  
The resistance-temperature behavior of thermistors is highly dependent  
upon the manufacturing process. Therefore, thermistor curves are not  
standardized to the extent that thermocouple or RTD curves are  
standardized. Typically, thermistor manufacturers supply the  
resistance-versus-temperature curves or tables for their particular devices.  
You can, however, approximate the thermistor curve relatively accurately  
with the Steinhart-Hart equation:  
1
T(°K) = -----------------------------------------------------------------  
a + b[ln(RT)] + c[ln(RT)]3  
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where  
T(°K) is the temperature in degrees Kelvin, equal to T(°C) + 273.15.  
RT is the resistance of the thermistor.  
a, b, and c are coefficients obtained from the thermistor manufacturer  
or calculated from the resistance-versus-temperature curve.  
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5
Using the SCXI-1503  
This chapter makes suggestions for developing your application and  
provides basic information regarding calibration.  
Developing Your Application in NI-DAQmx  
Note If you are not using an NI ADE, using an NI ADE prior to version 8.1, or are using  
an unlicensed copy of an NI ADE, additional dialog boxes from the NI License Manager  
appear allowing you to create a task or global channel in unlicensed mode. These messages  
continue to appear until you install version 8.1 or later of an NI ADE.  
This section describes how to configure and use NI-DAQmx to control the  
SCXI-1503 in LabVIEW, LabWindows/CVI, and Measurement Studio.  
These ADEs provide greater flexibility and access to more settings than  
MAX, but you can use ADEs in conjunction with MAX to quickly create a  
customized application.  
Typical Program Flowchart  
Figure 5-1 shows a typical program voltage measurement flowchart for  
creating a task to configure channels, take a measurement, analyze the data,  
present the data, stop the measurement, and clear the task.  
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No  
Yes  
Create Task Using  
DAQ Assistant?  
Create a Task  
Programmatically  
Create Task in  
DAQ Assistant  
or MAX  
Yes  
Create Channel  
Create Another  
Channel?  
No  
Hardware  
Timing/Triggering?  
No  
No  
Further Configure  
Channels?  
Yes  
Adjust Timing Settings  
Yes  
Configure Channels  
Yes  
Analyze Data?  
No  
Process  
Data  
Start Measurement  
Read Measurement  
Yes  
Display Data?  
No  
Graphical  
Display Tools  
Yes  
Continue Sampling?  
No  
Stop Measurement  
Clear Task  
Figure 5-1. Typical Program Flowchart for Voltage Measurement Channels  
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General Discussion of Typical Flowchart  
The following sections briefly discuss some considerations for a few of the  
steps in Figure 5-1. These sections are meant to give an overview of some  
of the options and features available when programming with NI-DAQmx.  
Creating a Task Using DAQ Assistant or  
Programmatically  
When creating an application, you must first decide whether to create the  
appropriate task using the DAQ Assistant or programmatically in the ADE.  
Developing your application using DAQ Assistant gives you the ability to  
configure most settings such as measurement type, selection of channels,  
excitation voltage, signal input limits, task timing, and task triggering. You  
can access the DAQ Assistant through MAX or your NI ADE. Choosing to  
use the DAQ Assistant can simplify the development of your application.  
NI recommends creating tasks using the DAQ Assistant for ease of use,  
when using a sensor that requires complex scaling, or when many  
properties differ between channels in the same task.  
If you are using an ADE other than an NI ADE, or if you want to explicitly  
create and configure a task for a certain type of acquisition, you can  
programmatically create the task from your ADE using functions or VIs.  
If you create a task using the DAQ Assistant, you can still further configure  
the individual properties of the task programmatically with functions  
or property nodes in your ADE. NI recommends creating a task  
programmatically if you need explicit control of programmatically  
adjustable properties of the DAQ system.  
Programmatically adjusting properties for a task created in the DAQ  
Assistant overrides the original, or default, settings only for that session.  
The changes are not saved to the task configuration. The next time you load  
the task, the task uses the settings originally configured in the DAQ  
Assistant.  
Adjusting Timing and Triggering  
There are several timing properties that you can configure through the  
DAQ Assistant or programmatically using function calls or property nodes.  
If you create a task in the DAQ Assistant, you can still modify the timing  
properties of the task programmatically in your application.  
When programmatically adjusting timing settings, you can set the task to  
acquire continuously, acquire a buffer of samples, or acquire one point at a  
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time. For continuous acquisition, you must use a while loop around the  
acquisition components even if you configured the task for continuous  
acquisition using MAX or the DAQ Assistant. For continuous and buffered  
acquisitions, you can set the acquisition rate and the number of samples to  
read in the DAQ Assistant or programmatically in your application. By  
default, the clock settings are automatically set by an internal clock based  
on the requested sample rate. You also can select advanced features such as  
clock settings that specify an external clock source, internal routing of the  
clock source, or select the active edge of the clock signal.  
Configuring Channel Properties  
All ADEs used to configure the SCXI-1503 access an underlying set of  
NI-DAQmx properties. Table 5-1 shows some of these properties. You can  
use Table 5-1 to determine what kind of properties you need to set to  
configure the module for your application. For a complete list of  
NI-DAQmx properties, refer to your ADE help file.  
Note You cannot adjust some properties while a task is running. For these properties, you  
must stop the task, make the adjustment, and re-start the application. Tables 5-1  
through 5-3 assume all properties are configured before the task is started.  
Table 5-1. NI-DAQmx Voltage Measurement Properties  
DAQ  
Assistant  
Property  
Short Name  
Description  
Accessible  
Analog Input»Maximum AI.Max  
Value  
Specifies the maximum value  
you expect to measure. The  
SCXI-1503 gain and E/M  
Series DAQ device range are  
computed automatically from  
this value.  
Yes  
Analog Input»Minimum  
Value  
AI.Min  
Specifies the minimum value  
you expect to measure. The  
SCXI-1503 gain and E/M  
Series DAQ device range are  
computed automatically from  
this value.  
Yes  
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Table 5-1. NI-DAQmx Voltage Measurement Properties (Continued)  
DAQ  
Assistant  
Accessible  
Property  
Short Name  
AI.Gain  
Description  
Analog Input»General  
Properties»Advanced»  
Gain and Offset»Gain  
Value  
Specifies a gain factor to apply  
to the signal conditioning  
portion of the channel. The  
SCXI-1503 supports 1 or 100.  
No  
Analog Input»General  
Properties»Advanced»  
High Accuracy Settings»  
Auto Zero Mode  
AI.AutoZeroMode Specifies when to measure  
ground. NI-DAQmx subtracts  
the measured ground voltage  
from every sample. The  
Yes  
SCXI-1503 supports None or  
Once.  
Analog Input»General  
Properties»Advanced»  
Input Configuration»  
Coupling  
AI.Coupling  
Specifies the input coupling of  
the channel. The SCXI-1503  
supports DC and GND  
coupling.  
No  
Table 5-2. NI-DAQmx RTD Measurement Properties  
DAQ  
Assistant  
Accessible  
Property  
Short Name  
Description  
Analog Input»Temperature»  
RTD»Type  
AI.RTD.Type  
Specifies the type of  
RTD connected to the  
channel.  
Yes  
Yes  
Analog Input»Temperature»  
RTD»R0  
AI.RTD.R0  
Specifies the  
resistance in ohms of  
the sensor at 0 °C.  
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Table 5-2. NI-DAQmx RTD Measurement Properties (Continued)  
DAQ  
Assistant  
Accessible  
Property  
Short Name  
AI.RTD.A  
AI.RTD.B  
AI.RTD.C  
Description  
Analog Input»Temperature»  
RTD»Custom»A, B, C  
Specifies the A, B, or  
C constant of the  
Callendar-Van Dusen  
equation when using a  
custom RTD type.  
Yes  
Analog Input»General  
Properties»Signal  
AI.Resistance.Cfg Specifies the  
resistance  
Yes  
Conditioning»Resistance  
Configuration  
configuration for the  
channel, such as  
2-wire, 3-wire, or  
4-wire.  
Table 5-3. NI-DAQmx Thermistor Measurement Properties  
DAQ  
Assistant  
Accessible  
Property  
Short Name  
Description  
Analog Input»Temperature»  
Thermistor»R1  
AI.Thrmistr.R1  
Specifies the resistance in  
ohms of the sensor at 0 °C.  
Yes  
Analog Input»Temperature»  
Thermistor»Custom»A, B, C  
AI.Thrmistr.A  
AI.Thrmistr.B  
AI.Thrmistr.C  
Specifies the A, B, or C  
constant of the Steinhart-Hart  
thermistor equation, which  
NI-DAQmx uses to scale  
thermistors.  
Yes  
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Table 5-4. NI-DAQmx Thermocouple Measurement Properties  
DAQ  
Assistant  
Accessible  
Property  
Short Name  
Description  
Analog Input»Temperature»  
Thermocouple»Type  
AI.Thermcpl.Type  
Specifies the type of  
thermocouple  
connected to the  
channel.  
Yes  
Analog Input»Temperature»  
Thermocouple»CJC Source  
AI.Thermcpl.CJCSrc  
AI.Thermcpl.CJCVal  
Indicates the source of  
cold-junction  
compensation.  
Yes  
Yes  
Analog Input»Temperature»  
Thermocouple»CJC Value  
Specifies the  
temperature of the  
cold-junction if the  
CJC source is constant  
value.  
Analog Input»Temperature»  
Thermocouple»CJC Channel  
AI.Thermcpl.CJCChan Indicates the channel  
that acquires the  
Yes  
temperature of the  
cold junction if CJC is  
channel.  
Note This is not a complete list of NI-DAQmx properties and does not include every  
property you may need to configure your application. It is a representative sample of  
important properties to configure for voltage measurements. For a complete list of  
NI-DAQmx properties and more information about NI-DAQmx properties, refer to your  
ADE help file.  
Acquiring, Analyzing, and Presenting  
After configuring the task and channels, you can start the acquisition, read  
measurements, analyze the data returned, and display it according to the  
needs of your application. Typical methods of analysis include digital  
filtering, averaging data, performing harmonic analysis, applying a custom  
scale, or adjusting measurements mathematically.  
NI provides powerful analysis toolsets for each NI ADE to help you  
perform advanced analysis on the data without requiring you to have a  
programming background. After you acquire the data and perform any  
required analysis, it is useful to display the data in a graphical form or log  
it to a file. NI ADEs provide easy-to-use tools for graphical display, such as  
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charts, graphs, slide controls, and gauge indicators. NI ADEs have tools  
that allow you to easily save the data to files such as spread sheets for easy  
viewing, ASCII files for universality, or binary files for smaller file sizes.  
Completing the Application  
After you have completed the measurement, analysis, and presentation of  
the data, it is important to stop and clear the task. This releases any memory  
used by the task and frees up the DAQ hardware for use in another task.  
Note In LabVIEW, tasks are automatically cleared.  
Developing an Application Using LabVIEW  
This section describes in more detail the steps shown in the typical program  
flowchart in Figure 5-1, such as how to create a task in LabVIEW and  
configure the channels of the SCXI-1503. If you need more information or  
for further instructions, select Help»VI, Function, & How-To Help from  
the LabVIEW menu bar.  
Note Except where otherwise stated, the VIs in Table 5-5 are located on the Functions»  
All Functions»NI Measurements»DAQmx - Data Acquisition subpalette and  
accompanying subpalettes in LabVIEW.  
Table 5-5. Programming a Task in LabVIEW  
Flowchart Step  
VI or Program Step  
Create Task in DAQ Assistant  
Create a DAQmx Task Name Controllocated on the  
Controls»All Controls»I/O»DAQmx Name Controls  
subpalette, right-click it, and select New Task (DAQ  
Assistant).  
Create a Task  
Programmatically  
(optional)  
DAQmx Create Task.vilocated on the Functions»All  
Functions»NI Measurements»DAQmx - Data Acquisition»  
DAQmx Advanced Task Options subpalette—This VI is  
optional if you created and configured the task using the DAQ  
Assistant. However, if you use it in LabVIEW, any changes you  
make to the task are not saved to a task in MAX.  
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Table 5-5. Programming a Task in LabVIEW (Continued)  
VI or Program Step  
Flowchart Step  
Create Virtual Channel(s)  
DAQMX Create Virtual Channel.vilocated on the  
Functions»All Functions»NI Measurements»DAQmx - Data  
Acquisition subpalette—Use this VI to add virtual channels to  
the task. Select the type of virtual channel based on the  
measurement you plan to perform.  
Adjust Timing Settings  
(optional)  
DAQmx Timing.vi(Sample Clock by default)—This VI is  
Assistant. Any timing settings modified with this VI are not  
saved in the DAQ Assistant. They are only available for the  
present session.  
Configure Channels  
(optional)  
NI-DAQmx Channel Property Node, refer to the Using a  
NI-DAQmx Channel Property Node in LabVIEW section for  
more information. This step is optional if you created and fully  
configured the channels using the DAQ Assistant. Any channel  
modifications made with a channel property node are not saved  
in the task in the DAQ Assistant. They are only available for the  
present session.  
Start Measurement  
Read Measurement  
Analyze Data  
DAQmx Start Task.vi  
DAQmx Read.vi  
Some examples of data analysis include filtering, scaling,  
harmonic analysis, or level checking. Some data analysis tools  
are located on the Functions»Signal Analysis subpalette and on  
the Functions»All Functions»Analyze subpalette.  
Display Data  
You can use graphical tools such as charts, gauges, and graphs  
to display the data. Some display tools are located on the  
Controls»All Controls»Numeric»Numeric Indicator  
subpalette and Controls»All Controls»Graph subpalette.  
Continue Sampling  
For continuous sampling, use a While Loop. If you are using  
hardware timing, you also need to set the DAQmx Timing.vi  
sample mode to Continuous Samples. To do this, right-click the  
terminal of the DAQmx Timing.vilabeled sample mode and  
click Create»Constant. Click the box that appears and select  
Continuous Samples.  
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Table 5-5. Programming a Task in LabVIEW (Continued)  
Flowchart Step  
VI or Program Step  
Stop Measurement  
DAQmx Stop Task.vi(This VI is optional, clearing the task  
automatically stops the task.)  
Clear Task  
DAQmx Clear Task.vi  
Using a NI-DAQmx Channel Property Node in  
LabVIEW  
You can use property nodes in LabVIEW to manually configure the  
channels. To create a LabVIEW property node, complete the following  
steps:  
1. Launch LabVIEW.  
2. Create the property node in a new VI or in an existing VI.  
3. Open the block diagram view.  
4. From the Functions toolbox, select All Functions»NI  
Measurements»DAQmx - Data Acquisition, and select DAQmx  
Channel Property Node.  
5. The ActiveChans property is displayed by default. This allows you to  
specify exactly what channel(s) you want to configure. If you want to  
configure several channels with different properties, separate the lists  
of properties with another Active Channels box and assign the  
appropriate channel to each list of properties.  
Note If you do not use Active Channels, the properties are set on all of the channels in  
the task.  
6. Right-click ActiveChans, and select Add Element. Left-click the new  
ActiveChans box. Navigate through the menus, and select the  
property you wish to define.  
7. Change the property to read or write to either get the property or write  
a new value. Right-click the property, go to Change To, and select  
Write, Read, or Default Value.  
8. After you have added the property to the property node, right-click the  
terminal to change the attributes of the property, add a control,  
constant, or indicator.  
9. To add another property to the property node, right-click an existing  
property and left-click Add Element. To change the new property,  
left-click it and select the property you wish to define.  
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Note Refer to the LabVIEW Help for information about property nodes and specific  
NI-DAQmx properties.  
Specifying Channel Strings in NI-DAQmx  
Use the channel input of DAQmx Create Channel to specify the  
SCXI-1503 channels. The input control/constant has a pull-down menu  
showing all available external channels. The strings take one of the  
following forms:  
single device identifier/channel number—for example SC1Mod1/ai0  
multiple, noncontinuous channels—for example SC1Mod1/ai0,  
SC1Mod1/ai4.  
multiple continuous channels—for example SC1Mod1/ai0:4  
(channels 0 through 4)  
When you have a task containing SCXI-1503 channels, you can set the  
properties of the channels programmatically using the DAQmx Channel  
Property Node.  
Text Based ADEs  
You can use text based ADEs such as LabWindows/CVI, Measurement  
Studio, Visual Basic 6, .NET, and C# to create code for using the  
SCXI-1503.  
LabWindows/CVI  
LabWindows/CVI works with the DAQ Assistant in MAX to generate  
code for an voltage measurement task. You can then use the appropriate  
function call to modify the task. To create a configurable channel or task in  
LabWindows/CVI, complete the following steps:  
1. Launch LabWindows/CVI.  
2. Open a new or existing project.  
3. From the menu bar, select Tools»Create/Edit DAQmx Tasks.  
4. Choose Create New Task In MAX or Create New Task In Project  
to load the DAQ Assistant.  
5. The DAQ Assistant creates the code for the task based on the  
parameters you define in MAX and the device defaults. To change  
a property of the channel programmatically, use the  
DAQmxSetChanAttributefunction.  
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Note Refer to the NI LabWindows/CVI Help for more information on creating NI-DAQmx  
tasks in LabWindows/CVI and NI-DAQmx property information.  
Measurement Studio (Visual Basic 6, .NET, and C#)  
When creating an voltage measurement task in Visual Basic 6, .NET and  
C#, follow the general programming flow in Figure 5-1. You can then use  
the appropriate function calls to modify the task. This example creates a  
new task and configures an NI-DAQmx voltage measurement channel on  
the SCXI-1503. You can use the same functions for Visual Basic 6, .NET  
and C#.  
The following text is a function prototype example:  
void AIChannelCollection.CreateVoltageChannel(  
System.String physicalChannelName,  
System.String nameToAssignChannel,  
System.Double minVal,  
System.Double maxVal);  
To actually create and configure the channel, you would enter something  
resembling the following example code:  
Task myTask = new  
NationalInstruments.DAQmx.Task(“myTaskName”);  
MyTask.DAQmxCreateAIVoltageChan (  
“SC1Mod1/ai0”, // System.String physicalChannelName  
“Voltage0”, // System.String nameToAssignChannel  
-10.0, // System.Double minVal  
10.0); // System.Double maxVal  
// setting attributes after the channel is created  
AIChannel myChannel = myTask.AIChannels[“Voltage0”];  
myChannel.AutoZeroMode = kAutoZeroTypeOnce;  
Modify the example code above or the code from one of the shipping  
examples as needed to suit your application.  
Note You can create and configure the voltage measurement task in MAX and  
load it into your application with the function call  
NationalInstruments.DAQmx.DaqSystem.Local.LoadTask.  
Refer to the NI Measurement Studio Help for more information on creating NI-DAQmx  
tasks in LabWindows/CVI and NI-DAQmx property information.  
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Programmable NI-DAQmx Properties  
All of the different ADEs that configure the SCXI-1503 access an  
underlying set of NI-DAQmx properties. Tables 5-1 through 5-4 provide a  
list of some of the properties that configure the SCXI-1503. You can use  
this list to determine what kind of properties you need to set to configure  
the device for your application. For a complete list of NI-DAQmx  
properties, refer to your ADE help file.  
Note Tables 5-1 through 5-4 are not complete lists of NI-DAQmx properties and do not  
include every property you may need to configure voltage measurements. It is a  
representative sample of important properties to configure voltage measurements. For a  
complete list of NI-DAQmx properties and more information on NI-DAQmx properties,  
refer to your ADE help file.  
Calibration  
The SCXI-1503 is shipped with a calibration certificate and is calibrated at  
the factory to the specifications described in Appendix A, Specifications.  
Calibration constants are stored inside the calibration EEPROM and  
provide software correction values your application development software  
uses to correct the measurements for both offset and gain errors in the  
module.  
Internal/Self-Calibration  
You can self-calibrate the SCXI-1503 in MAX by right-clicking the  
module and selecting Self Calibrate. The NI-DAQmx Self Calibrate Device  
function does the same. A self-calibration of the SCXI-1503 grounds all the  
input channels and stores the resulting measurement as an offset correction  
constant on the module. You should perform a self-calibration every time  
you install the SCXI-1503 to a new system.  
Note You should self-calibrate the connected DAQ device before self-calibrating the  
SCXI-1503.  
External Calibration  
If you have an accurate calibrator and DMM, you can externally calibrate  
the SCXI-1503 gain and offset constants using NI-DAQmx functions. You  
can also calibrate the 100 μA current excitation.  
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The functions that are required for externally calibrating the SCXI-1503 are  
available in NI-DAQmx 8.1 or later. Refer to the NI-DAQmx Help for  
details about these functions.  
Most external calibration documents for SCXI modules are available to  
download from ni.com/calibrationby clicking Manual Calibration  
Procedures. For external calibration of modules not listed there, Basic  
Calibration Service or Detailed Calibration Service is recommended. You  
can get information about both of these calibration services from  
ni.com/calibration. NI recommends performing an external  
calibration once a year.  
Note Performing an external calibration of the SCXI-1503 permanently overwrites the  
factory calibration settings, which impacts the accuracy of the inputs.  
SCXI-1503 User Manual  
5-14  
ni.com  
 
A
Specifications  
This appendix lists the specifications for the SCXI-1503 modules.  
These specifications are typical at 25 °C unless otherwise noted.  
Analog Input  
Input Characteristics  
Number of channels ............................... 16 differential  
Input coupling ........................................ DC  
Input signal ranges ................................. 100 mV (gain = 100) or  
10 V (gain = 1)  
Input overvoltage protection  
Powered on ..................................... 42 VDC  
Powered off..................................... 25 V  
Inputs protected............................... AI<0..15>  
CJ sensor input protection............... 15 VDC powered on or off  
Transfer Characteristics  
Nonlinearity ........................................... 0.005% FSR  
Input offset error (RTI)  
Gain = 1  
Calibrated 1 .............................. 650 μV max  
250 μV typ  
With autozero enabled 2 ........... 300 μV max  
150 μV typ  
1
Assumes 1,000 point average, 25 °C 10 °C over one year.  
Assumes 1,000 point average, 1 °C of autozero temperature.  
2
© National Instruments Corporation  
A-1  
SCXI-1503 User Manual  
 
           
Appendix A  
Specifications  
Gain = 100  
Calibrated1................................ 25 μV max  
10 μV typ  
With autozero enabled2 ............ 10 μV max  
5 μV typ  
Gain error (relative to calibration reference)  
Gain = 1 or 100  
Calibrated1................................0.074% of reading max  
0.02% of reading typ  
RTD Measurement Accuracy  
Table A-1. RTD Measurement Accuracy  
Measured  
Temperature °C  
100 Ω Max °C  
100 Ω Typ °C  
0.23  
1000 Ω Max °C  
1000 Ω Typ °C  
–100 to 0  
0.60  
0.62  
0.69  
1.11  
2.06  
1.09  
1.11  
1.20  
1.68  
2.81  
0.46  
0.47  
0.49  
0.65  
1.04  
0 to 25  
0.23  
25 to 100  
0.25  
100 to 500  
500 to 1200  
0.37  
0.65  
Notes: The accuracies in this table reflect using the module in4-wire mode. They do not include errors from the RTD  
including lead-wire errors when using 2- or 3-wire connection.  
The accuracies assume auto-zero is enabled and the environmental conditions are 25 °C 10 °C over a one year period.  
These accuracies were computed using a standard RTD with a TCR of 3851.  
Amplifier Characteristics  
Input coupling.........................................DC  
Input impedance  
Normal powered on.........................>1 GΩ  
Input bias current.................................... 2.8 nA  
1
2
Assumes 1,000 point average, 25 °C 10 °C over one year.  
Assumes 1,000 point average, 1 °C of autozero temperature.  
SCXI-1503 User Manual  
A-2  
ni.com  
 
   
Appendix A  
Specifications  
CMRR characteristics (DC to 60 Hz)  
Gain 1.............................................. –75 dB min  
–90 dB typ  
Gain 100.......................................... –106 dB min  
–110 dB typ  
Output range........................................... 10 V  
Output impedance .................................. 91 Ω  
Dynamic Characteristics  
Minimum scan interval (per channel, any gain)  
0.012% accuracy........................... 3 μs  
0.0061% accuracy......................... 10 μs  
0.0015% accuracy......................... 20 μs  
Noise characteristics (RTI)  
Gain = 1  
10 Hz to 1 MHz .............................. 100 μVrms  
Gain = 100  
10 Hz to 1 MHz .............................. 1 μVrms  
0.1 to 10 Hz..................................... 0.5 μVp-p  
Filter  
Cutoff frequency (–3 dB)....................... 5 Hz  
NMR (60 Hz) ......................................... –40 dB min  
Step response characteristics (gain 1 or 100)  
To 0.0015%..................................... 0.6 s  
Stability  
Recommended warm-up time ................ 20 min  
Offset temperature coefficient  
Gain = 1 .......................................... 35 μV/°C max  
10 μV/°C typ  
Gain = 100 ...................................... 1.5 μV/°C max  
0.5 μV/°C typ  
© National Instruments Corporation  
A-3  
SCXI-1503 User Manual  
 
     
Appendix A  
Specifications  
Gain temperature coefficient  
(gain 1 or 100) ........................................ 15 ppm/°C max  
5 ppm/°C typ  
Excitation  
Channels .................................................16 single-ended outputs  
Current output.........................................100 μA  
Accuracy................................................. 0.05%  
Temperature drift.................................... 5 ppm/°C  
Output voltage compliance.....................10 V  
Maximum resistive load .........................100 kΩ  
Overvoltage protection ........................... 40 VDC  
Measurement Category...........................CAT I  
Power Requirements From SCXI Backplane  
V+ ...........................................................18.5 to 25 VDC, 170 mA  
V– ...........................................................–18.5 to –25 VDC, –170 mA  
+5 V ........................................................+4.75 to 5.25 VDC, 50 mA  
Environmental  
Operating temperature ............................0 to 50 °C  
Storage temperature................................–20 to 70 °C  
Humidity.................................................10 to 90% RH, noncondensing  
Maximum altitude...................................2,000 meters  
Pollution Degree (indoor use only) ........2  
SCXI-1503 User Manual  
A-4  
ni.com  
 
     
Appendix A  
Specifications  
Physical  
3.0 cm  
(1.2 in.)  
17.2 cm  
(6.8 in.)  
18.8 cm  
(7.4 in.)  
Figure A-1. SCXI-1503 Dimensions  
Weight.................................................... 745 g (26.3 oz)  
Maximum Working Voltage  
Maximum working voltage refers to the signal voltage plus the  
common-mode voltage.  
Signal + common mode ......................... Each input should remain  
within 10 V of AI GND  
© National Instruments Corporation  
A-5  
SCXI-1503 User Manual  
 
     
Appendix A  
Specifications  
Safety  
This product is designed to meet the requirements of the following  
standards of safety for electrical equipment for measurement, control,  
and laboratory use:  
IEC 61010-1, EN-61010-1  
UL 61010-1, CSA 61010-1  
Note For UL and other safety certifications, refer to the product label or visit  
ni.com/certification, search by model number or product line, and click the  
appropriate link in the Certification column.  
Electromagnetic Compatibility  
This product is designed to meet the requirements of the following  
standards of EMC for electrical equipment for measurement, control,  
and laboratory use:  
EN 61326 EMC requirements; Minimum Immunity  
EN 55011 Emissions; Group 1, Class A  
CE, C-Tick, ICES, and FCC Part 15 Emissions; Class A  
Note For EMC compliance, operate this device according to product documentation.  
CE Compliance  
This product meets the essential requirements of applicable European  
Directives, as amended for CE marking, as follows:  
73/23/EEC; Low-Voltage Directive (safety)  
89/336/EEC; Electromagnetic Compatibility Directive (EMC)  
Note Refer to the Declaration of Conformity (DoC) for this product for any additional  
regulatory compliance information. To obtain the DoC for this product, visit  
ni.com/certification, search by model number or product line, and click the  
appropriate link in the Certification column.  
Waste Electrical and Electronic Equipment (WEEE)  
EU Customers At the end of their life cycle, all products must be sent to a WEEE recycling  
center. For more information about WEEE recycling centers and National Instruments  
WEEE initiatives, visit ni.com/environment/weee.htm.  
SCXI-1503 User Manual  
A-6  
ni.com  
 
     
B
Removing the SCXI-1503  
This appendix explains how to remove the SCXI-1503 from MAX and an  
SCXI chassis or PXI/SCXI combination chassis.  
Removing the SCXI-1503 from MAX  
To remove a module from MAX, complete the following steps after  
launching MAX:  
1. Expand Devices and Interfaces.  
2. Click the + next to NI-DAQmx to expand the list of installed chassis.  
3. Click the + next to the appropriate chassis to expand the list of installed  
modules.  
4. Right-click the module or chassis you want to delete and click Delete.  
5. A confirmation window opens. Click Yes to continue deleting the  
module or chassis or No to cancel this action.  
Note Deleting the SCXI chassis deletes all modules in the chassis. All configuration  
information for these modules is also lost.  
The SCXI chassis and/or SCXI module(s) should now be removed from the  
list of installed devices in MAX.  
Removing the SCXI-1503 from a Chassis  
Consult the documentation for the chassis and accessories for additional  
instructions and precautions. To remove the SCXI-1503 module from a  
chassis, complete the following steps while referring to Figure B-1:  
1. Power off the chassis. Do not remove the SCXI-1503 module from a  
chassis that is powered on.  
2. If the SCXI-1503 is the module cabled to the E/M Series DAQ device,  
disconnect the cable.  
3. Remove any terminal block that connects to the SCXI-1503.  
© National Instruments Corporation  
B-1  
SCXI-1503 User Manual  
 
     
Appendix B  
Removing the SCXI-1503  
4. Rotate the thumbscrews that secure the SCXI-1503 to the chassis  
counterclockwise until they are loose, but do not completely remove  
the thumbscrews.  
Remove the SCXI-1503 by pulling steadily on both thumbscrews until the  
module slides completely out.  
6
5
®
1
5
4
3
2
1
ARDES  
4
SCXI  
M
A
IN  
F
R
A
M
E
S
C
X
I
1
1
0
0
2
3
1
2
Cable  
SCXI Module Thumbscrews  
3
4
SCXI-1503  
Terminal Block  
5
6
SCXI Chassis Power Switch  
SCXI Chassis  
Figure B-1. Removing the SCXI-1503  
SCXI-1503 User Manual  
B-2  
ni.com  
 
   
C
Common Questions  
This appendix lists common questions related to the use of the SCXI-1503.  
Which version of NI-DAQ works with the SCXI-1503, and how do I get  
the most current version of NI-DAQ?  
You must have NI-DAQ 8.1 or later. Visit the NI Web site at ni.comand  
select Download Software»Drivers and Updates»Search Drivers and  
Updates. Enter the keyword NI-DAQto find the latest version of NI-DAQ  
for your operating system.  
I cannot correctly test and verify that my SCXI-1503 is working. What  
should I do?  
Unfortunately, there is always the chance that one or more components in  
the system are not operating correctly. You may have to call or email a  
technical support representative. The technical support representative often  
suggests troubleshooting measures. If requesting technical support by  
phone, have the system nearby so you can try these measures immediately.  
NI contact information is listed in the Technical Support Information  
document.  
Can the SCXI-1503 current outputs be interactively controlled in  
MAX or programmatically controlled using NI-DAQ function calls,  
LabVIEW, or Measurement Studio?  
No. The current-output level is 100 μA as long as the chassis is powered on.  
You cannot power off or adjust the current output using MAX, NI-DAQ  
function calls, or an ADE such as LabVIEW or Measurement Studio. If you  
require this functionality, consider using an SCXI-1124 module or NI 670X  
device instead.  
How can I ground a floating voltage measurement?  
You can use the IEX– terminal of each channel as a ground reference. Refer  
to the SCXI-1306 Terminal Block Installation Guide for details about using  
the SCXI-1306 DIP switches to control ground referencing.  
© National Instruments Corporation  
C-1  
SCXI-1503 User Manual  
 
         
Appendix C  
Common Questions  
Can I connect N current-output channels in parallel to create a  
precision current source that provides N × 100 μA?  
Yes, you can connect the current output in parallel. When connecting the  
output in parallel, connect the appropriate IEX+ terminals together and the  
corresponding IEX– terminals together.  
Can I connect N current-output channels in series to achieve a higher  
terminal-voltage compliance limit?  
No. Each current source is ground referenced. Therefore, you cannot place  
multiple current-outputs in series.  
Are the SCXI-1503 channels isolated with respect to each other, the  
E/M Series DAQ device, or ground?  
No. The SCXI-1503 does not contain any isolation circuitry. If you require  
isolation, consider the SCXI-1124 or SCXI-1125 module instead.  
Can I modify the SCXI-1503 circuitry to generate current at a level  
different than 100 μA?  
No. Do not attempt to modify any circuitry in the SCXI-1503.  
Are there any user-serviceable parts inside the SCXI-1503?  
No. There are no fuses, potentiometers, switches, socketed resistors, or  
jumpers inside the module. Disassembly of the module for any reason can  
void its warranty and nullify its accuracy specification.  
Can I access the unused analog-input channels of the E/M Series DAQ  
device if it is directly cabled to the SCXI-1503 in a single-chassis  
system?  
Yes. E/M Series DAQ device channels 1 through 7 are available to measure  
unconditioned signals. Use an SCXI-1180 or the 50-pin breakout connector  
on the SCXI-1346 or SCXI-1349 cable adapter to route signals to these  
channels.  
Which digital lines are unavailable on the E/M Series DAQ device if I  
am cabled to an SCXI-1503 module?  
Table 2-4 shows the digital lines that are used by the SCXI-1503 for  
communication and scanning. These lines are unavailable for  
general-purpose digital I/O if the SCXI-1503 is connected to the  
E/M Series DAQ device.  
SCXI-1503 User Manual  
C-2  
ni.com  
 
   
Appendix C  
Common Questions  
Does short-circuiting a current-output channel do any damage to the  
SCXI-1503?  
No. The SCXI-1503 delivers 100 μA into any load from 0 Ω to 100 kΩ.  
Does open-circuiting a current-output channel damage the  
SCXI-1503? What is the open-circuit voltage level?  
No. An SCXI-1503 current-output channel is not damaged if no load is  
connected. The open-circuit voltage is 12.4 VDC.  
© National Instruments Corporation  
C-3  
SCXI-1503 User Manual  
 
 
Glossary  
Symbol  
Prefix  
micro  
milli  
Value  
10– 6  
10–3  
103  
µ
m
k
kilo  
M
mega  
106  
Numbers/Symbols  
%
percent  
+
positive of, or plus  
negative of, or minus  
plus or minus  
less than  
<
/
per  
°
degree  
Ω
ohms  
+5 V (signal)  
+5 VDC source signal  
A
A
amperes  
ADE  
application development environment such as LabVIEW,  
LabWindows/CVI, Visual Basic, C, and C++  
AI  
analog input  
AI GND  
analog input ground signal  
© National Instruments Corporation  
G-1  
SCXI-1503 User Manual  
 
 
Glossary  
B
bit  
one binary digit, either 0 or 1  
C
CE  
European emissions control standard  
chassis ground signal  
C GND  
channel  
pin or wire lead to which you apply, or from which you read, an analog or  
digital signal. Analog signals can be single-ended or differential. For digital  
signals, channels (also known as lines) are grouped to form ports.  
chassis  
the enclosure that houses, powers, and controls SCXI modules  
clock input signal  
CLK  
common-mode voltage  
current excitation  
voltage that appears on both inputs of a differential amplifier  
a source that supplies the current needed by a sensor for its proper operation  
D
D/A  
D*/A  
DAQ  
digital-to-analog  
Data/Address  
data acquisition—(1) collecting and measuring electrical signals from  
sensors, transducers, and test probes or fixtures and processing the  
measurement data using a computer; (2) collecting and measuring the same  
kinds of electrical signals with A/D and/or DIO devices plugged into a  
computer, and possibly generating control signals with D/A and/or DIO  
devices in the same computer  
DAQ device  
DAQ D*/A  
a data acquisition device. Examples are E/M Series data acquisition devices  
the data acquisition device data/address line signal used to indicate whether  
the SER DAT IN pulse train transmitted to the SCXI chassis contains data  
or address information  
device  
a plug-in data acquisition device, module, card, or pad that can contain  
multiple channels and conversion devices. SCXI modules are distinct from  
devices, with the exception of the SCXI-1200, which is a hybrid.  
SCXI-1503 User Manual  
G-2  
 
ni.com  
Glossary  
D GND  
digital ground signal  
differential amplifier  
an amplifier with two input terminals, neither of which are tied to a ground  
reference, whose voltage difference is amplified  
DIN  
DIO  
DoC  
Deutsche Industrie Norme (German Industrial Standard)  
digital input/output  
Declaration of Conformity  
drivers/driver  
software  
software that controls a specific hardware device such as an E/M Series  
DAQ device  
E
EMC  
electromagnetic compliance  
electromagnetic interference  
EMI  
excitation  
EXT CLK  
a voltage or current source used to energize a sensor or circuit  
external clock signal  
G
gain  
the factor by which a signal is amplified, sometimes expressed in decibels  
I
ID  
identifier  
IEX+  
positive excitation channel  
negative excitation channel  
inch or inches  
IEX–  
in.  
input impedance  
the measured resistance and capacitance between the input terminals of a  
circuit  
© National Instruments Corporation  
G-3  
SCXI-1503 User Manual  
 
Glossary  
J
jumper  
a small rectangular device used to connect two adjacent posts on a circuit  
board. Jumpers are used on some SCXI modules and terminal blocks to  
either select certain parameters or enable/disable circuit functionality.  
L
lead resistance  
the small resistance of a lead wire. The resistance varies with the lead  
length and ambient temperature. If the lead wire carries excitation current,  
this varying resistance can cause measurement error.  
M
m
meters  
M
(1) Mega, the standard metric prefix for 1 million or 106, when used with  
units of measure such as volts and hertz; (2) mega, the prefix for 1,048,576,  
or 220, when used with B to quantify data or computer memory  
MISO  
master-in-slave-out signal  
MOSI  
master-out-slave-in signal  
multiplex  
multiplexed mode  
to route one of many input signals to a single output  
an SCXI operating mode in which analog input channels are multiplexed  
into one module output so that the cabled E/M Series DAQ device has  
access to the multiplexed output of the module as well as the outputs of all  
other multiplexed modules in the chassis  
N
NC  
not connected (signal)  
NI-DAQ  
the driver software needed in order to use National Instruments E/M Series  
DAQ devices and SCXI components  
NI-DAQmx  
The latest NI-DAQ driver with new VIs, functions, and development tools  
SCXI-1503 User Manual  
G-4  
ni.com  
 
Glossary  
O
output voltage  
compliance  
the largest voltage that can be generated across the output of a current  
source without the current going out of specification  
OUT REF  
output reference signal  
P
ppm  
parts per million  
PXI  
PCI eXtensions for Instrumentation—an open specification that builds on  
the CompactPCI specification by adding instrumentation-specific features  
R
RL  
lead resistance  
RMA  
Return Material Authorization  
RSVD  
RTD  
reserved bit, pin, or signal  
resistance-temperature detector  
S
s
seconds  
samples  
S
scan  
one or more analog samples taken at the same time, or nearly the same time.  
Typically, the number of input samples in a scan is equal to the number of  
channels in the input group. For example, one scan, acquires one new  
sample from every analog input channel in the group.  
SCAN CLK  
scan clock signal used to increment to the next channel after each  
E/M Series DAQ device analog-to-digital conversion  
SCXI  
Signal Conditioning eXtensions for Instrumentation  
SCXIbus  
located in the rear of an SCXI chassis, the SCXIbus is the backplane that  
connects modules in the same chassis to each other  
© National Instruments Corporation  
G-5  
SCXI-1503 User Manual  
 
Glossary  
sensor  
a type of transducer that converts a physical phenomenon into an electrical  
signal  
SER CLK  
serial clock signal used to synchronize digital data transfers over the  
SER DAT IN and SER DAT OUT lines  
SER DAT IN  
SER DAT OUT  
signal conditioning  
Slot 0  
serial data input signal  
serial data output signal  
the manipulation of signals to prepare them for digitizing  
refers to the power supply and control circuitry in the SCXI chassis  
slot 0 select signal  
SLOT 0 SEL  
SPI CLK  
serial peripheral interface clock signal  
T
thermistor  
a thermally sensitive resistor  
Traditional NI-DAQ  
(Legacy)  
An upgrade to the earlier version of NI-DAQ. Traditional NI-DAQ  
(Legacy) has the same VIs and functions and works the same way as  
NI-DAQ 6.9.x. You can use both Traditional NI-DAQ (Legacy) and  
NI-DAQmx on the same computer, which is not possible with NI-DAQ  
6.9.x.  
transducer  
a device capable of converting energy from one form to another  
U
UL  
Underwriters Laboratory  
V
V
volts  
VAC  
VDC  
volts, alternating current  
volts, direct current  
SCXI-1503 User Manual  
G-6  
ni.com  
 
Glossary  
VI  
virtual instrument—(1) a combination of hardware and/or software  
elements, typically used with a PC, that has the functionality of a classic  
stand-alone instrument; (2) a LabVIEW software module (VI), which  
consists of a front panel user interface and a block diagram program  
virtual channels  
channel names that can be defined outside the application and used without  
having to perform scaling operations  
W
W
watts  
© National Instruments Corporation  
G-7  
SCXI-1503 User Manual  
 
Index  
Numerics  
2-wire configuration of resistive devices, 2-4  
3-wire resistive sensor  
cables, custom, 2-1  
connected in 2-wire configuration, 2-5  
circuitry  
digital control, 4-3  
A
adjusting timing and triggering, 5-3  
AI 0 signal, multiplexing, 2-11  
amplifier characteristics specifications, A-2  
analog circuitry  
CJC source/value, 3-2  
common questions, C-1  
common software-configurable settings  
CJC source/value, 3-2  
analog input channels, 4-3  
CJ SENSOR, 4-3  
gain/input range, 3-1  
configuration, 3-1  
analog input channels, 4-3  
analog input signal connections, 2-1  
ground-referencing of signals, 2-2  
analog input signals, multiplexed, 4-4  
analog input specifications, A-1  
amplifier characteristics, A-2  
applications  
task, 3-3  
verifying signal, 3-4  
NI-DAQmx, 3-4  
configuring channel properties, 5-4  
connecting resistive devices to SCXI-1503, 2-2  
2-wire configuration, 2-4  
configuration, 2-5  
presenting, 5-7  
completing, 5-8  
LabVIEW, 5-8  
program flowchart (figure), 5-2  
programmable properties, 5-13  
specifying channel strings, 5-11  
4-wire configuration, 2-3  
lead-resistance compensation  
using 3-wire resistive sensor  
and two matched current  
sources, 2-6  
© National Instruments Corporation  
I-1  
SCXI-1503 User Manual  
 
 
Index  
DAQ Assistant, 5-3  
developing an application, 5-8  
programmatically, 5-3  
current output channels, questions  
about, C-1, C-3  
current sources, operating, 4-4  
custom cables, 2-1  
programming a task (table), 5-8  
using a NI-DAQmx channel property  
LabWindows/CVI  
D
DAQ device  
maximum working voltage specifications, A-5  
Measurement & Automation Explorer  
configurable settings, 3-2  
removing the SCXI-1503, B-1  
measurement properties, NI-DAQmx  
RTD (table), 5-5  
accessing unused analog input  
channels, C-2  
DAQ devices  
digital control circuitry, 4-3  
thermistor (table), 5-6  
thermocouple (table), 5-7  
voltage (table), 5-4  
Measurement Studio  
E
creating code for using SCXI-1503, 5-12  
multiplexed mode operation  
theory, 4-4  
E/M Series DAQ devices, 4-4  
electromagnetic compatibility  
multiplexing  
environment specifications, A-4  
SCXI-1503, 4-4  
F
front connector  
NI-DAQmx  
pin assignments (table), 2-8  
developing applications, 5-1  
acquiring, analyzing, and  
presenting, 5-7  
G
gain/input range, configuration, 3-1  
adjusting timing and triggering, 5-3  
completing, 5-8  
configuring channel properties, 5-4  
LabVIEW, 5-8  
I
input characteristics specifications, A-1  
installation into SCXI chassis, 1-4  
SCXI-1503 User Manual  
I-2  
 
ni.com  
Index  
NI-DAQmx channel property  
program flowchart (figure), 5-2  
specifying channel strings, 5-11  
thermistor measurement properties  
(table), 5-6  
two matched current sources, 2-6  
RTDs (resistive-temperature detectors)  
measurement errors, 4-6  
overview, 4-5  
thermocouple measurement properties  
temperature, 4-6  
voltage measurement properties  
(table), 5-4  
O
safety specifications, A-6  
calibration, 5-13  
common questions, C-1  
common software settings, 3-1  
communication signals (table), 2-11  
configuration settings, 3-1  
major components, 4-3  
measurements, 3-3  
P
physical specifications, A-5  
pin assignments  
power requirements from SCXI  
backplane, A-4  
removing (figure), B-2  
taking measurements. See measurements  
using  
Q
questions and answers, C-1  
Measurement Studio to create  
code, 5-12  
R
descriptions, 2-11  
removing the SCXI-1503  
Explorer, B-1  
SCXIbus  
connector, 4-3  
interface, 4-3  
resistive devices, connecting to SCXI-1503  
2-wire configuration, 2-4  
3-wire resistive sensor connected to  
2-wire configuration, 2-5  
4-wire configuration, 2-3  
self-test verification, troubleshooting, C-1  
signal connections  
analog input, 2-1  
front connector  
pin assignments (table), 2-8  
© National Instruments Corporation  
I-3  
SCXI-1503 User Manual  
 
Index  
signals  
(figure), 4-7  
thermistors  
verifying, 3-4  
NI-DAQmx, 3-4  
overview, 4-10  
software, NI-DAQ version required, C-1  
specifications  
(figure), 4-11  
analog input, A-1  
CE compliance, A-6  
electromagnetic compatibility, A-6  
theory of multiplexed operation, 4-4  
theory of operation  
filters, A-3  
maximum working voltage, A-5  
analog circuitry, 4-3  
digital circuitry, 4-3  
rear signal connector, 4-3  
theory of multiplexed operation, 4-4  
(table), 5-6  
backplane, A-4  
safety, A-6  
stability, A-3  
NI-DAQmx, 5-11  
thermistors  
measurement circuits, 4-11  
resistance-temperature curve  
T
taking measurements. See measurements  
transducers, 4-5  
connecting resistive devices to  
SCXI-1503, 2-2  
thermocouple, measurement properties  
(table), 5-7  
3-wire resistive sensor connected in  
lead resistance compensation  
matched current sources, 2-6  
RTDs  
timing and triggering, adjusting, 5-3  
transfer characteristics specifications, A-1  
V
verifying  
signal, 3-4  
measurement errors, 4-6  
overview, 4-5  
temperature, 4-6  
NI-DAQmx, 3-4  
troubleshooting, C-1  
Visual Basic  
creating code for the SCXI-1503, 5-11  
SCXI-1503 User Manual  
I-4  
 
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