Solution
There are two versions of the NI 9237, one has a Dsub connector and the other one has RJ-50 connectors. The connection of the external excitation will depend on these variants, you can find the pinout of both connectors on page 10 of the NI 9237 Getting Started Guide. The excitation pins for each channel are also listed below:
Dsub
Excitation Voltage Source: Vex+/Vex- 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- in the front of the module. To access the EX+/EX- for each channel you need the NI 9942 connector:
- 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