Connecting Strain Gauges, Shunt Resistors and Quarter Bridge Accessory to the NI-9237

Updated May 8, 2024

Reported In


  • NI-9237
  • NI-9944
  • NI-9945
  • NI-9949

Issue Details

  • What external connections do I need to make in order to take readings from my strain gauges or load cell?
  • How do I connect the NI-9237 to my strain gauge or bridge-based sensor?
  • How do I perform shunt calibration with NI-9237?
  • How do I connect the NI-9944/9945 accessory to my strain gauge or bridge-based sensor?


The NI-9237 is a bridge and strain measurement module. It can be configured for quarter, half, and full bridge measurements for both 120Ω and 350Ω bridge completion. Accessories are needed for quarter bridge measurements (see Quarter Bridge section below). A shunt resistor and half-bridge competition resistors are built into the NI-9237.


This module is designed for Wheatstone bridge measurements as seen in the image below:


It is important to note that the numbering of the Wheatstone bridge arms is not arbitrary.  The resistor values are used in complex equations to calculate the strain or expected voltage.  The resistor name definition can be summarized as follows:

  • R1 is defined between EX + & AI - 
  • R2 is defined between EX - & AI -
  • R3 is defined between EX - & AI +
  • R4 is defined between EX + & AI +

The NI-9237 has 10 pins for each channel. These pins, with either the DSUB connector or the NI-9949 accessory, correspond to:

Pin 1SCShunt Resistor end 1
Pin 2AI+Channel Input +
Pin 3AI- Channel Input -
Pin 4RS+Remote Sense +
Pin 5RS-Remote Sense -
Pin 6EX+Excitation +
Pin 7EX-Excitation -
Pin 8T+TEDS+
Pin 9T-TEDS-
Pin 10SCShunt Resistor end 2

Below we illustrate the external connections necessary to take measurements from various types of strain gauges and the external connections needed for shunt calibration.

Full Bridge:

  • Note: We can see the internal shunt resistor (Rs). It does not matter which SC pin is connected to which side of R3. When shunt calibration is being performed, the internal switch closes to connect the resistor. During normal operation of the module, the switch remains open.
  • Note: You can use remote sensing to continuously and automatically correct for errors in excitation leads which generally is most appropriate for half- and full-bridge sensors. Connect remote sense terminals (RS+ and RS-) to the points where the excitation voltage wires connect to the bridge circuit. For additional details on the remote sensing, configuration refer to the NI-9237 Datasheet.
  • Note: You can program the NI-9237 to supply 2.5 V, 3.3 V, 5 V, or 10 V of excitation voltage. The maximum excitation power for internal excitation is 150 mW. If you need to supply higher than that, please use external excitation, for additional details on how to configure it please refer to the following article: Use External Excitation with the NI-9237 Module.
  • Note: If your strain gauges only has 4 wires, then you do not need to connect the two wires for shunt calibration.
  • Note: The NI-9949 accessory can be used with the NI-9237 RJ50 front connector as a feed-through terminal adapter.

Half Bridge / QuarterBridge II:


  • Note: We can see the NI-9237’s internal bridge completion resistors.  EX+, EX-, and AI+ will still need to be connected by the user.
  • Note: Quarter Bridge II configuration is connected to the NI-9237 as if it were a Half Bridge. R4 is the active quarter bridge strain gauge. R3 is a dummy resistor placed perpendicular to the direction of strain, and will therefore exhibit changes in resistance only due to temperature drift. When configuring the strain measurement task in software, you will need to select Quarter Bridge II in the task setup.
  • Note: The NI-9949 accessory can be used with the NI-9237 RJ50 front connector as a feed-through terminal adapter.


Quarter Bridge:


Additional Information

Read our white paper on measuring strain with strain gauges to learn more about bridge configuration options and which one best meets your needs

Shunt calibration is a process used to correct the system gain error of the NI-9237, which is introduced by the analog-to-digital converter. A strain is simulated by placing a shunt resistor of known value, Rs across one leg of a bridge sensor. The change in the total resistance of that leg will create a change in the voltage difference between the legs of the bridge, AI+, and AI-. The measured signal levels can then be compared with the expected signal levels, allowing software adjustments to be made to compensate for the gain errors. Typically, the shunt resistor is connected across R3, however, it is possible to use any of the Wheatstone bridge arms as long as it is specified as an input for the shunt calibration VI. See Shunt Calibration (Gain Adjustment)  for more information. The NI-9237 has an internal shunt resistor of 100kΩ.