Amplitude difference in P0.0 pulse on PXIe-6124

[TCjr]

Hi,

I've been examining the digital output pulse from P0.0 on the PXIe-6124 and noticed a difference in amplitude when measured on an Oscope vs on the PXIe-6124's Analog Input. The pulse measured on the Oscope has a 5vdc amplitude referenced to ground. That same pulse measured on the PXIe-6124's Analog Input is about 2.7vdc in amplitude with the low side at around -10.2vdc and the high side around -7.5vdc.

After that said, my concern is I'm using this P0.0 pulse to drive a solid state relay with a minimum turn-on level of 3.5vdc. I trust the output level of the external scope, but a little doubt is in my mind do to the difference in the amplitude levels measured. I'm just curious about the difference.

Tks, Terry

[crossrulz]

This sounds like you have the Analog Input set up wrong.  How do you have the AI configured and wired?

[TCjr]

Thanks for the reply...

I've attached screen shots of the results and setup of the VI. The VI I'm using to capture the ouput pulse is an example program taken from labview. Also, I get the same pulse values using MAX.

Tks, Terry

[crossrulz]

I am willing to bet that you do not have anything connected to the negative side of your AI (should be AI8).  Change your Terminal Configuration to be RSE (Referenced Single Ended).

[TCjr]

I just spotted the problem....I was hooked on AI GND instead of AI 0- for differential.....DUHHHH....My Bad!

thanks for letting me bounce that off of you....

[TCjr]

Just for information for you to base on....

I'm using the TB-2706 and the pinout description on the inside of the removable panel of the TB-2706 calls out PIN# 68 as AI 0 and Pin#34 as AI 8. Thats what got me thinking that I'm measuring in differential mode not relative to ground. Then I had to go back and reference the pinout drawing through MAX, which was very nice to have, but the labeling on the removable panel on the TB-2706 could have a more descriptive labeling.

Tks Again, Terry