Problem with PCI 6221 Analog input in RSE mode

[Tushar_Jambhekar]

We have a test system built using PCI 6221 and Other NI cards. 6221 is used for Aquiring Analog Inputs. All the AI channels are configured in RSE mode.

The system was working fine for years. and then it stopped working.

when we tested the AI channels in MAX all channels are drifting towards either -10V or +10V as if channel connection is floating.

we tested following things

1. We removed all the wires(coming from test system) connected to SCB68. and then shorted AI0 with AI GND. still AI0 RSE data is drifting towards -10V

2. We replaced the old PCI6221 with the new one still problem persist.

3. We replaced cable connecting PCI6221 and SCB 68, still problem persist.

4. We removed all PCI cards except 6221. Still problem persist.

5. if we short AI0 and digital ground then AI0 in RSE mode shows stable 0V Value

6 if we short AI0 with +5v (pin 😎 then AI0 in RSE mode shows stable 5.11V Value

what might be the problem and how we can resolve it.

[Shreyas]

Hi Tushar,

               I have tried connecting the 6221 in RSE mode from AI0 to AI GND and got 0 volts as the measured value. I would suggest you to use the DAQ diagnostic utility to detect the fault in your card. In case it turns out to be faulty, kindly contact the NI Local support team.

For India: support.india@ni.com

[Philipp Spiegel]

Hi folks,

I have the same problem; channels are drifting to either +10.6 or -10.6 Volts.

I already checked my 6221 with the DAQ diagnostic device, but there is no error.

What can I do?

Thanks for an answer.

Regards,

Philipp

[John_P1]

Hi Philipp,

It is not unusual for an unconnected channel to drift to the positive or negative voltage rail.  Is your channel connected to anything?  Are you in RSE, NRSE, or Differential mode?  Which pins do you have connected and to what?

In the case of the Original Poster, I would suggest to check for bent pins on his SCB-68.

Best Regards,

[Tushar_Jambhekar]

Thanks for the Reply

Actually i cant test it immidiately, as the system is with my client. and he is located in other city.

However when we tested the system we tried shorting several AIGND and DGND pins with AI0 (one by one), none of the AIGND pins showed 0V and all the DGND showed 0V.

We also tried this on other channels like AI1, AI2 etc. and results were same.

[kekin]

If you get chance to test it again at customer site do following:

Measure the 5V supply with respect DGND & AGND. IF with respect to AGND it does not show 5V, then DGND & AGND are not internally shorted & problem lies there.

2. As you said that connecting DGND to AI0 give 0V. So try to short DGND to AGND externally & then connect some other AGND line to AI0.'I think this is issue of AGND. Either problem with card or PCI supply.

3.If you have some other card(not 6221) with AGND & DGND on it then try to check for its shorting.

4.Put this 6221 card in some other slot & then try.

Hope this helps. Kudos are welcomed.

[Tushar_Jambhekar]

Thanks for your response

We also tried shorting AGND and DGND, but it affected the counter measurements. so we skipped that idea. also AI measurements were not accurate either.

we also tried changing PCI slot and changin the PC, nothing worked.

I will try to measure internal 5V supply wrt to AIGND

[chakko]

Hello Tushar,

Have you solved the problem? If yes could you please share it because I am currently having the same problem with my NI-daq 6221. I need your help on this.

Thanks...