National Instruments NI 9237E Series User manual

OPERATING INSTRUCTIONS AND SPECIFICATIONS
NI 9237E
4-Channel, 24-Bit Half/Full-Bridge Analog Input Module

NI 9237E Operating Instructions and Specifications 2 ni.com
This document describes how to use the National Instruments 9237E
and includes dimensions, pin assignments, and specifications for the
NI 9237E. In this document, the NI 9237E with RJ-50 connectors
and the NI 9237E with DSUB are referred to inclusively as the
NI 9237E. Visit ni.com/info and enter rdsoftwareversion to
determine which software you need for the modules you are using.
For information about installing, configuring, and programming the
system, refer to the system documentation. Visit ni.com/info and
enter cseriesdoc for information about C Series documentation.
Caution National Instruments makes no electromagnetic
compatibility (EMC) or CE marking compliance claims
for the NI 9237E. The end-product supplier is responsible
for conformity to any and all compliance requirements.
Caution The NI 9237E must be installed inside a suitable
enclosure prior to use. Hazardous voltages may be present.

© National Instruments Corp. 3 NI 9237E Operating Instructions and Specifications
NI 9237E Dimensions
The following figure shows the dimensions of the NI 9237E.
Figure 1. NI 9237E Dimensions in Millimeters (Inches)
73.4 (2.89)
0.0 (0.00)
26.7 (1.05) 58.4 (2.30) 66.0 (2.60)
0.0 (0.00)

NI 9237E Operating Instructions and Specifications 4 ni.com
Connecting the NI 9237E
The NI 9237E has four RJ-50 receptacles or a 37-pin DSUB
connector that provides connections for four half or full bridges,
and an external excitation voltage source.
Figure 2. NI 9237E with RJ-50 Pin Assignments
Ch 0
Ch 1
Ch 2
Ch 3
SC
AI+
AI–
RS+
RS–
EX+
EX–
T+
T–
SC
1
2
3
4
5
6
7
8
9
10
Ch0 – Ch3
EX+ EX+
EX– EX–

© National Instruments Corp. 5 NI 9237E Operating Instructions and Specifications
Figure 3. NI 9237E with DSUB Pin Assignments
1
2
3
4
5
6
7
8
9
10
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
RS0+
EX0+
AI0+
SC0+
RS1+
EX1+
AI1+
SC1+
T–
Vex+
RS2+
EX2+
AI2+
SC2+
RS3+
EX3+
AI3+
SC3+
T–
RS0–/SC0–
EX0–
AI0–
T0+
RS1–/SC1–
EX1–
AI1–
T1+
T–
Vex–
RS2–/SC2–
EX2–
AI2–
T2+
RS3–/SC3–
EX3–
AI3–
T3+

NI 9237E Operating Instructions and Specifications 6 ni.com
When you connect a half bridge to the NI 9237E, you must connect
the AI+, EX+ and EX–, and RS+ and RS– signals, but you do not
need to connect the AI– signal because it is connected internally.
When you connect a full bridge, you must connect the AI+ and
AI–, EX+ and EX–, and RS+ and RS– signals. Refer to Figure 4
for an illustration of how to connect half and full bridges to the
NI 9237E.
Note You can use a quarter bridge with the NI 9237E if
you add a resistor externally to create a half bridge. You
also can use a quarter bridge with the NI 9237E
with RJ-50 if you use the NI 9944 or NI 9945 Quarter
Bridge Completion Accessory. Visit ni.com and search
for the NI 9944 and NI 9945 Quarter Bridge Completion
Accessories for more information about these accessories
and how to purchase them.
Note National Instruments does not recommend using
an RJ-45 cable with the NI 9237E with RJ-50 because it
can physically damage pins 1 and 10 on the device, and
thus permanently disable shunt calibration no matter
what connector you use.

© National Instruments Corp. 7 NI 9237E Operating Instructions and Specifications
Note When you insert or remove a new sensor from the
NI 9237E, slight changes in the excitation voltages can
cause a mismatch between the internal half-bridge
completion resistors and the half-bridge sensors, which
results in a change in the measurement offsets.
National Instruments recommends performing bridge
calibrations of quarter- or half-bridge sensors after
connecting all sensors to the NI 9237E and after
removing or attaching any additional sensor. Visit
ni.com/info and enter the info code rdw9237 for more
information about changes in voltage offsets in the
NI 9237E.

NI 9237E Operating Instructions and Specifications 8 ni.com
Figure 4. Connecting a Half or Full Bridge to the NI 9237E
1NI9237E with DSUB only 2NI9237E with RJ-50 only
EX+
EX–
SC
SC
RS+
RS–
RS– /SC–
T+
T–
AI–
AI+
TEDS
NI 9237E
1
2

© National Instruments Corp. 9 NI 9237E Operating Instructions and Specifications
Each channel on the NI 9237E has an independent 24-bit ADC
and an input amplifier that enable you to sample signals from all
four channels simultaneously.
The NI 9237E is isolated from earth ground. However, the
individual channels are not isolated from each other. The EX+,
EX–, and T– signals are common among all channels. You can
connect the NI 9237E to a device that is biased at any voltage
within the NI 9237E rejection range of earth ground. Refer to the
Specifications section for more information about the
common-mode rejection ratio (CMRR).
You also can connect floating signals to the NI 9237E. If you
connect floating signals to the NI 9237E, National Instruments
recommends connecting the EX– signal to the earth ground or
shield for better noise rejection.
The NI 9237E also includes filters to prevent aliasing. The filters
on the NI 9237E filter according to the data rate. Refer to the
Understanding NI 9237E Filtering section for more information
about filtering.

NI 9237E Operating Instructions and Specifications 10 ni.com
Wiring TEDS Channels
Ensure that neither the TEDS data (T+) nor the TEDS return (T–)
signal is tied in common to any AI signals on the NI 9237E. The
NI 9237E connects all the T– signals together internally. The
NI 9237E with DSUB has only three T– pins. To connect four
TEDS sensors to the NI 9237E with DSUB, wire the TEDS return
signals of two of the sensors to one of the T– pins. Visit
ni.com/info and enter the info code rdteds for more
information about TEDS sensors.
Connection Options to Correct for Resistance Errors
Wiring resistance can create errors in bridge circuits. The
NI 9237E provides two mechanisms to correct for these errors:
remote sensing and shunt calibration.
Remote Sensing
Remote sensing continuously and automatically corrects for errors
in excitation leads, and generally is most appropriate for half- and
full-bridge sensors.
Long wire and small gauge wire have greater resistance, which can
result in gain error. The resistance in the wires that connect the
excitation voltage to the bridge causes a voltage drop, which is a