Solution
For a full bridge measurement, the 9237 is only measuring differential voltage and is independent of the nominal resistance of the strain gauge. The input impedance of the NI 9237 is essentially an open circuit and should not affect the bridge based measurement.
For the external excitation voltage, there are two versions of the 9237: One with a Dsub connector and one with RJ-50 connectors. You can find the pinout of both connector variants of the device in the NI 9237 Getting Started Guide. The excitation pins for each channel are also noted below:
Dsub
Excitation Voltage Source: V_EX+/V_EX- on pins 10/29
- Ch 0: EX0+/EX0- on pins 2/21
- Ch 1: EX1+/EX1- on pins 6/25
- Ch 2: EX2+/EX2- on pins 12/31
- Ch 3: EX3+/EX3- on pins 16/35
RJ-50
Excitation Voltage Source: EX+/EX- on
NI 9942 connector. It will be used if you are hooking up the external excitation to the NI 9237 module
- Ch 0: EX+/EX- on pins 6/7 on CH0
- Ch 1: EX+/EX- on pins 6/7 on CH1
- Ch 2: EX+/EX- on pins 6/7 on CH2
- Ch 3: EX+/EX- on pins 6/7 on CH3