scb 68 terminal block (5 V between D GND and pfi)

[scchae]

I'm using two daq boards, 6036e and 6731 with a SCB 68 terminal block. If I check the voltage between D GND and PFI line of the SCB 68 terminal block for both daq boards, I can see 5 V difference between them for any GND and PFI lines. so, I can not use the trigger using GND and PFI line. Is it broken or normal? 

FYI, so I'm using two PFI lines, which are not biased with 5 V, for the trigger. In that case, the only falling edge works no matter what i choose the rasing or falling edge for the trigger. 

[GerdW]

Hi scchae,

why don't you read the manual of your DAQ devices?

They mention some "pull-ip to +5Vdc" for the digital IO lines (for the 6036e): no wonder you will measure +5V between PFI and DGND…

[scchae]

Dear GerdW,

Thank you for your reply. So, the hardware is normal. That is, any GND are referenced with +5 Vdc.(Q, why do they give a +5 Vdc pin more?) If I need real electric ground, I have to couple the terminal block with a real device which sends the trigger signal, not use any GND pin. Am I right?

Thank you for advance

SC

[GerdW · Accepted solution]

Hi scchae,

That is, any GND are referenced with +5 Vdc.

No, GND is GND. All other pins are referenced to GND…

Do you know the meaning of "pull-up resistors"?

why do they give a +5 Vdc pin more?

Because that +5Vdc pin can be used as a (small) power supply to external devices.

If I need real electric ground, I have to couple the terminal block with a real device which sends the trigger signal, not use any GND pin. Am I right?

No.

You should connect GND with your external device GND.

There are manuals from NI describing several possible connections!

[scchae]

Dear GerdW

Thank you for all your replies. Now, I understood how to measure the signal using DAQ board. 

Best regards,

SC