Channels got influenced by each other

[Noob_Labviewer]

Hi guys,

I'm quite new to LabVIEW, recently i'm setting up a small system to measure the pressure and temperature simultaneously. A PCI-6071E card is used, AI0 and AI1 are connected to pressure transducer and thermocouple output respectively. The actual voltages of the two channels should be 1.67 and 0.23 . When I activate only one input, both signals are accurate. But when I activate the two signals together, the pressure terminal reading is OK as 1.67, but the temperature terminal reading will increase to 0.26(but the actual voltage is still 0.23 as measured by multimeter), when i deactivate the pressure transducer, the temperature voltage will be 0.23 again.

Anyone can tell me why?

Cheers,

Pengcheng

[crossrulz]

Sounds like the MUX is not given enough time to settle before the ADC takes it measurement.  Try slowing down your sample rate.  Another trick would be to add a channel that is grounded and have the DAQ measure that grounded signal between your two channels.

[Noob_Labviewer]

Thanks for your reply. I set the sample rate to 1Hz and also tried the other way, but I'm afraid that they didn't work. It's reaaaly weird.

[SFuller]

Hi,

The issue sounds like ghosting between channels. Please find the following resources which may solve this issue:

How Do I Eliminate Ghosting from My Measurements?

Troubleshooting Unexpected Voltages, Floating, or Crosstalk on Analog Input Channels

I hope this helps!