Take a look at page 9 of this link. http://www.ni.com/pdf/manuals/323493b.pdf
It's not clear, but I am going to guess that the extra power cable is designed for the V and C terminals that would be present if you were using a CB-1 connector block?
Seeing this question came at just the right time for me. For my latest cFP system, I decided to use the 37 pin cable and a socket to terminal board on DIN rail
|778672-01||CB-37FV 37-Pin Screw Terminal Block, Vertical, DIN Rail Mount|
I just got into really connecting everything up and testing out the cFP operation with the external devices and sensors. I discovered I forgot to hook up voltage and common to the boards so that digital inputs and outputs would work right. If I had seen the cable with power cord before now, I could have bought that and used it.
In then end, I realized that the terminal board only goes up to 32 (so there are 5 unused numbers) I discovered that V is on pins 33 and 34. Common is on pins 35 and 36 on the terminal board and in the cable. (I still don't know what pin 37 is for.)
I had to discover this with a continuity checker on my CB1 terminal block. I wasn't able to find on NI's documentation online any good wiring diagram of a cable or CB1 board to describe the functions of all 37 pins. The module manuals were fine for telling what pins 1 through 32 did. But nothing I have yet discovered showed pins 33 through 37. I just thing there could be some better documentation either with the terminal board or in the I/O module manuals as to what pin numbers are associated with the "extra" pins.
Thanks all, My question was answered.
BTW, I believe pin 37 is used in the special case where thermocouples are used as inputs and need a cold junction compensation.
Hi Ravens Fan,
I will enter a product suggestion to improve the documentation for the cables. Thank you for your suggestion.
Page 7 of the Compact FieldPoint Operating instructions lists what pins 33-37 do. You are right in saying that pins 33/34 are V and 35/36 are common. Pin 37 is a CJC terminal.
Let me know if you need more detailed information.
Thank you Karunya.
For some reason I had not seen that documentation page before.
JDowell, that was a good pickup on pin 37 being the CJC!