National Instruments SCXI-1503 User Manual

TM

SCXI

SCXI-1503 User Manual

March 2007
374271A-01

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The SCXI-1503 is warranted against defects in materials and workmanship for a period of one year from the date of shipment, as evidenced
by receipts or other documentation. National Instruments will, at its option, repair or replace equipment that proves to be defective during the
warranty period. This warranty includes parts and labor.

The media on which you receive National Instruments software are warranted not to fail to execute programming instructions, due to defects
in materials and workmanship, for a period of 90 days from date of shipment, as evidenced by receipts or other documentation. National
Instruments will, at its option, repair or replace software media that do not execute programming instructions if National Instruments receives
notice of such defects during the warranty period. National Instruments does not warrant that the operation of the software shall be
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A Return Material Authorization (RMA) number must be obtained from the factory and clearly marked on the outside of the package before
any equipment will be accepted for warranty work. National Instruments will pay the shipping costs of returning to the owner parts which are
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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.

Contents

Chapter 1
About the SCXI-1503

What You Need to Get Started ......................................................................................1-1

National Instruments Documentation ............................................................................1-2

Installing Application Software, NI-DAQ, and the E/M Series DAQ Device ..............1-4

Installing the SCXI-1503 Module into the SCXI Chassis...............................1-4

Installing the Terminal Block..........................................................................1-4

Configuring the SCXI System Software .........................................................1-4

Verifying the SCXI-1503 Installation............................................................................1-5

Chapter 2
Connecting Signals

Analog Input Signal Connections ..................................................................................2-1

Ground-Referencing the Signals .....................................................................2-2

Connecting Resistive Devices to the SCXI-1503 ..........................................................2-2

4-Wire Configuration ......................................................................................2-3

2-Wire Configuration ......................................................................................2-4

3-Wire Resistive Sensor Configuration...........................................................2-5

Lead-Resistance Compensation Using a 3-Wire Resistive Sensor

and Two Matched Current Sources ..............................................................2-6

Front Connector .............................................................................................................2-7

Rear Signal Connector ...................................................................................................2-10

Rear Signal Connector Descriptions ...............................................................2-11

Chapter 3
Configuring and Testing

SCXI-1503 Software-Configurable Settings .................................................................3-1

Common Software-Configurable Settings ......................................................3-1

Gain/Input Range ..............................................................................3-1

Input Coupling ..................................................................................3-2

CJC Source/Value .............................................................................3-2

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 v SCXI-1503 User Manual

Contents

Chapter 4
Theory of Operation

Rear Signal Connector, SCXIbus Connector, and SCXIbus Interface.......................... 4-3

Digital Control Circuitry ............................................................................................... 4-3

Analog Circuitry............................................................................................................ 4-3

Analog Input Channels.................................................................................... 4-3

Operation of the Current Sources .................................................................................. 4-4

Theory of Multiplexed Operation.................................................................................. 4-4

Measuring Temperature with Resistive Transducers .................................................... 4-5

RTDs ............................................................................................................... 4-5

RTD Measurement Errors ................................................................ 4-6

The Relationship Between Resistance and Temperature in RTDs... 4-6

Thermistors ..................................................................................................... 4-10

Thermistor Measurement Circuits .................................................... 4-11

Resistance/Temperature Characteristic of Thermistors.................... 4-12

Chapter 5
Using the SCXI-1503

Developing Your Application in NI-DAQmx............................................................... 5-1

Typical Program Flowchart ............................................................................ 5-1

General Discussion of Typical Flowchart....................................................... 5-3

Creating a Task Using DAQ Assistant or Programmatically ........... 5-3

Adjusting Timing and Triggering..................................................... 5-3

Configuring Channel Properties ....................................................... 5-4

Acquiring, Analyzing, and Presenting.............................................. 5-7

Completing the Application.............................................................. 5-8

Developing an Application Using LabVIEW ................................................. 5-8

Using a NI-DAQmx Channel Property Node in LabVIEW ............. 5-10

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

SCXI-1503 User Manual vi ni.com

Appendix A
Specifications

Appendix B
Removing the SCXI-1503

Appendix C
Common Questions

Glossary

Index

Figures

Figure 2-1. 4-Wire Resistive Sensor Connected in a 4-Wire Configuration ...........2-3

Figure 2-2. 2-Wire Resistive Sensor Connected in a 2-Wire Configuration ...........2-4

Figure 2-3. 3-Wire Resistive Sensor Configuration.................................................2-5

Figure 2-4. 3-Wire Configuration Using Matched Current Sources........................2-6

Contents

Figure 4-1. Block Diagram of SCXI-1503...............................................................4-2

Figure 4-2. 2-Wire RTD Measurement....................................................................4-6

Figure 4-3. Resistance-Temperature Curve for a 100 Ω Platinum RTD,

α = 0.00385 ...........................................................................................4-7

Figure 4-4. Resistance-Temperature Curve for a 2,252 Ω Thermistor ....................4-11

Figure 4-5. Thermistor Measurement with Constant Current Excitation ................4-11

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 vii SCXI-1503 User Manual

Contents

Tables

Table 1-1. Supported SCXI-1503 Terminal Blocks ............................................... 1-4

Table 2-1. Front Signal Pin Assignments .............................................................. 2-8

Table 2-2. Signal Descriptions ............................................................................... 2-9

Table 2-3. Rear Signal Pin Assignments................................................................ 2-10

Table 2-4. SCXI-1503 50-Pin Rear Connector Signals ........................................ 2-11

Table 4-1. Platinum RTD Types ............................................................................ 4-8

Table 5-1. NI-DAQmx Voltage Measurement Properties ..................................... 5-4

Table 5-2. NI-DAQmx RTD Measurement Properties ......................................... 5-5

Table 5-3. NI-DAQmx Thermistor Measurement Properties ............................... 5-6

Table 5-4. NI-DAQmx Thermocouple Measurement Properties .......................... 5-7

Table 5-5. Programming a Task in LabVIEW ...................................................... 5-8

Table A-1. RTD Measurement Accuracy ............................................................... A-2

SCXI-1503 User Manual viii ni.com

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.

1

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 1-1 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

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

™

/CVI™,

❑ Tools

– Wire cutter

– Wire stripper

– Flathead screwdriver

– 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 1-2 ni.com

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
the latest version of NI-DAQ, click Drivers and Updates at

© National Instruments Corporation 1-3 SCXI-1503 User Manual

ni.com/manuals. To download

ni.com.

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 Ye s Resistive temperature

measurements

TBX-96 No Custom signals

SCXI-1310 No

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 1-4 ni.com

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.

Chapter 1 About the SCXI-1503

© National Instruments Corporation 1-5 SCXI-1503 User Manual

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.

2

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 2-1 SCXI-1503 User Manual

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.

SCXI-1503 User Manual 2-2 ni.com

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.

Chapter 2 Connecting Signals

+
–

SCXI-1503

Channel X

I = 100 µA

External Sensor SCXI-1306

R

L1

R

L2

R

T

R

L4

R

L3

IEX+

AI+

AI–

IEX–

CH X

ON

Figure 2-1. 4-Wire Resistive Sensor Connected in a 4-Wire Configuration

© National Instruments Corporation 2-3 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 (V
excitation current (I

R

the error voltage is:

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.

) is introduced into the measurement equal to the

E

) times the sum of the two lead resistances, RL1 and

EX

. If we assume equal lead resistances, RL1= RL2= RL, the magnitude of

L2

V

2RLI

=

E

SCXI-1306External Sensor SCXI-1503

R

L1

R

T

R

L2

IEX+

AI+

AI–

IEX–

EX

Channel X

+
–

I = 100 µA

CH X

ON

Figure 2-2. 2-Wire Resistive Sensor Connected in a 2-Wire Configuration

SCXI-1503 User Manual 2-4 ni.com

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

R

and therefore RL2 is the only lead resistance that introduces an error into

L3

the measurement. The resulting measurement error is:

VE RL2I

=

Chapter 2 Connecting Signals

EX

SCXI-1306External Sensor

R

L1

R

R

T

L3

R

L2

IEX+

AI+

AI–

IEX–

CH X

ON

+
–

SCXI-1503

Channel X

I = 100 µA

Figure 2-3. 3-Wire Resistive Sensor Configuration

© National Instruments Corporation 2-5 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.

SCXI-1306External Sensor

R

L1

R

T

R

L2

R

L3

EX0+

AI0+

AI0–

EX0–

ON

EX1+

AI1+

AI1–

EX1–

ON

+
–

+
–

SCXI-1503

I = 100 µA

I = 100 µA

Figure 2-4. 3-Wire Configuration Using Matched Current Sources

SCXI-1503 User Manual 2-6 ni.com

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 R
and R

are series opposing, relative to the inputs of the differential

L2

amplifier, eliminating their effect on the voltage measured across R

L1

.

T

Note R

and RL2 are assumed to be equal.

L1

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 2-7 SCXI-1503 User Manual

Chapter 2 Connecting Signals

Table 2-1. Front Signal Pin Assignments

Front Connector Diagram Pin Number Column A Column B Column C

32 GND AI0– AI0+

Column

A B C

32

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

NC—no connection

RSVD—reserved

31 GND AI1– AI1+

30 GND AI2– AI2+

29 GND AI3– AI3+

28 RSVD AI4– AI4+

27 RSVD AI5– AI5+

26 RSVD AI6– AI6+

25 RSVD AI7– AI7+

24 NC IEX0– IEX0+

23 NC IEX1– IEX1+

22 NC IEX2– IEX2+

21 NC IEX3– IEX3+

20 RSVD IEX4– IEX4+

19 RSVD IEX5 IEX5+

18 NC IEX6– IEX6+

17 NC IEX7– IEX7+

16 GND AI8– AI8+

15 GND AI9– AI9+

14 GND AI10– AI10+

13 GND AI11– AI11+

12 NC AI12– AI12+

11 NC AI13– AI13+

10 NC AI14– AI14+

9 NC AI15– AI15+

8 NC IEX8– IEX8+

7 NC IEX9– IEX9+

6 NC IEX10– IEX10+

5 NC IEX11– IEX11+

4 CJ SENSOR IEX12– IEX12+

3 CJ SENSOR IEX13– IEX13+

2 CGND IEX14– IEX14+

1 +5 V IEX15– IEX15+

SCXI-1503 User Manual 2-8 ni.com

Chapter 2 Connecting Signals

Table 2-2. Signal Descriptions

Pin Signal Name Description

A1 +5 V +5 VDC Source—Used to power circuitry on the

terminal block. 0.1 mA of source not protected.

A13 – A16,

GND Ground—Tied to the SCXI module ground.

A29 – A32

A1, A19, A20,
A25 – A28

RSVD Reserved—This pin is reserved. Do not connect

any signal to this pin.

A2 C GND 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

C32 – C25,
C16 – C9

AI <0..7> –,
AI <8..15> –

AI <0..7> +,
AI <8..15> +

Negative Input Channels—Negative side of
differential input channels.

Positive Input Channels—Positive side of
differential input channels.

© National Instruments Corporation 2-9 SCXI-1503 User Manual

Chapter 2 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 Pin Number Pin Number Signal Name

AI GND 1 2 AI GND

AI 0 + 3 4 AI 0 –

NC 5 6 NC

12

34

56

78

910

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 7 8 NC

NC 9 10 NC

NC 11 12 NC

NC 13 14 NC

NC 15 16 NC

NC 17 18 NC

NC 19 20 NC

NC 21 22 NC

NC 23 24 DIG GND

SER DAT IN 25 26 SER DAT OUT

DAQ D*/A 27 28 NC

SLOT 0 SEL* 29 30 NC

NC 31 32 NC

DIG GND 33 34 NC

NC 35 36 SCAN CLK

SER CLK 37 38 NC

NC 39 40 NC

NC 41 42 NC

RSVD 43 44 NC

NC 45 46 RSVD

NC means no connection.

RSVD means reserved.

SCXI-1503 User Manual 2-10 ni.com

NC 47 48 NC

NC 49 50 NC

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

Pin

Signal Name

1, 2 AI GND AI GND — Analog input ground—connects to

3 AI 0 + AI 0 + Input Channel 0 positive—used to

Device Signal

Name

Direction Description

the analog input ground of the DAQ
device.

differentially multiplex all
16 channels, the CJ sensor, and
analog signals from the modules to
the connected DAQ device.

4 AI 0 – AI 0 – Input 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 D GND — Digital ground—these pins supply

the reference for E/M Series DAQ
device digital signals and are
connected to the module digital
ground.

25 SER DAT IN P0.0 Input Serial data in—this signal taps into

the SCXIbus MOSI line to send
serial input data to a module or
Slot 0.

© National Instruments Corporation 2-11 SCXI-1503 User Manual