National Instruments 24-Bit Half/Full-Bridge Analog Input Module NI... User manual

OPERATING INSTRUCTIONS AND SPECIFICATIONS
NI 9237
4-Channel, 24-Bit Half/Full-Bridge Analog Input Module
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NI 9237 Operating Instructions and Specifications 2 ni.com
This document describes how to use the National Instruments 9237
and includes specifications and pin assignments for the NI 9237.
Visit ni.com/info and enter rdsoftwareversion to determine
which software youneed for the modules youare 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.
Note The safety guidelines and specifications in this
document are specific to the NI 9237. The other
components in the system might not meet the same safety
ratings and specifications. Refer to the documentation for
each component in the system to determine the safety
ratings and specifications for the entire system. Visit
ni.com/info and enter cseriesdoc for information
about C Series documentation.

© National Instruments Corp. 3 NI 9237 Operating Instructions and Specifications
Safety Guidelines
Operate the NI 9237 only as described in these operating
instructions.
Hot Surface This icon denotes that the component may be
hot. Touching this component may result in bodily injury.
Safety Guidelines for Hazardous Locations
The NI 9237 is suitable for use in Class I, Division 2, Groups A, B,
C, D, T4 hazardous locations; Class I, Zone 2, AEx nC IIC T4, and
Ex nC IIC T4 hazardous locations; and nonhazardous locations
only. Follow these guidelines if youare installing the NI 9237 in a
potentially explosive environment. Not following these guidelines
may result in serious injury or death.
Caution Do not disconnect I/O-side wires or connectors
unless power has been switched off or the area is known
to be nonhazardous.
Caution Do not remove modules unless power has been
switched off or the area is known to be nonhazardous.

NI 9237 Operating Instructions and Specifications 4 ni.com
Caution Substitution of components may impair
suitability for Class I, Division 2.
Caution For Zone 2 applications, install the system
in an enclosure rated to at least IP 54 as defined by
IEC 60529 and EN 60529.
Caution For Zone 2 applications, connected signals must
be within the following limits:
Capacitance .......................... 0.2 μF max
Inductance ............................ 80 mH max
Special Conditions for Hazardous Locations Use in Europe
This equipment has been evaluated as EEx nC IIC T4 equipment
under DEMKO Certificate No. 03 ATEX 0324020X. Each module
is marked II 3G and is suitable for use in Zone 2 hazardous
locations. If youare using the NI 9237 in Gas Group IIC hazardous
locations or in ambient temperatures of –40 °C ≤Ta ≤70 °C, you
must use the device in an NI chassis that has been evaluated as
EEx nC IIC T4, Ex nA IIC T4, or Ex nL IIC T4 equipment.

© National Instruments Corp. 5 NI 9237 Operating Instructions and Specifications
Special Conditions for Marine Applications
Some modules are Lloyd’s Register (LR) Type Approved for
marine applications. To verify Lloyd’s Register certification, visit
ni.com/certification and search for the LR certificate, or
look for the Lloyd’s Register mark on the module.
Caution To meet radio frequency emission requirements
for marine applications, use shielded cables and install
the system in a metal enclosure. Suppression ferrites
must be installed on power supply inputs near power
entries to modules and controllers. Power supply and
module cables must be separated on opposite sides of the
enclosure and must enter and exit through opposing
enclosure walls.

NI 9237 Operating Instructions and Specifications 6 ni.com
Connecting the NI 9237
The NI 9237 has four RJ-50 receptacles that provide connections
for four half or full bridges.
Figure 1. NI 9237 Pin Assignments
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–
Ch 0
Ch 1
Ch 2
Ch 3

© National Instruments Corp. 7 NI 9237 Operating Instructions and Specifications
When youconnect a half bridge to the NI 9237, youmust connect
the AI+, EX–, and RS– signals, but youdo not connect the AI–
signal. When youconnect a full bridge, youmust connect the AI+,
AI–, EX–, and RS– signals. Refer to Figure 2 for an illustration of
how to connect half and full bridges to the NI 9237.
Note Youcan use a quarter bridge with the NI 9237 if
youadd a resistor externally to create a half bridge. You
also can use a quarter bridge with the NI 9237 if youuse
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 9237 because it can physically
damage pins 1 and 10 on the device, and thus
permanently disable shunt calibration no matter what
connector youuse.

NI 9237 Operating Instructions and Specifications 8 ni.com
The NI 9237 has a four-terminal external excitation voltage source
connector. Youcan use the EX+ and EX– terminals on the
connector to connect one external excitation voltage source to the
module. Youcan use the additional EX+ and EX– terminals on the
connector to wire multiple NI 9237 modules together in a daisy
chain.
Note When youinsert or remove a new sensor from the
NI 9237, 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 9237 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 9237.

© National Instruments Corp. 9 NI 9237 Operating Instructions and Specifications
Figure 2. Connecting a Half or Full Bridge to the NI 9237
EX+
EX–
SC
SC
RS+
RS–
T+
T–
AI–
AI+
TEDS
NI 9237

NI 9237 Operating Instructions and Specifications 10 ni.com
Each channel on the NI 9237 has an independent 24-bit ADC
and an input amplifier that enable youto sample signals from all
four channels simultaneously.
The NI 9237 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. Youcan connect the
NI 9237 to a device that is biased at any voltage within the NI 9237
rejection range of earth ground. Refer to the Specifications section
for more information about the common-mode rejection
ratio (CMRR).
Yo ualso can connect floating signals to the NI 9237. If you
connect floating signals to the NI 9237, National Instruments
recommends connecting the EX– signal to the earth ground or
shield for better noise rejection.
The NI 9237 also includes filters to prevent aliasing. The filters
on the NI 9237 filter according to the data rate. Refer to the
Understanding NI 9237 Filtering section for more information
about filtering.