05-17-2023 06:43 AM
I have a cDAQ-9178 with NI 9221 connected taking 3 pressure readings.
If a known pressure is applied to any channel, I get 5V
If the same pressure is applied to 2 channels, I get 2.5V
Everything is wired correctly.
Could someone point me in the right direction for next steps troubleshooting please?
Solved! Go to Solution.
05-17-2023 08:53 AM
It sounds like a ghosting issue. Try How Do I Eliminate Ghosting from My Measurements?
05-17-2023 09:34 AM
@ZYOng wrote:
It sounds like a ghosting issue. Try How Do I Eliminate Ghosting from My Measurements?
They're not adjacent, the channels are currently separated (using 0, 2 and 4) with 1 and 3 being left blank. It was previously connected to 0,1,2, but I spaced them to try and prevent any ghosting.
Setup is 3 x 1Bar pressure transducers on a 10V supply, max 5V output.
Sample rate is 1Hz Sample size 1
05-17-2023 09:36 AM
Could you please explain the connections and how you apply the signal?
05-17-2023 09:51 AM
@santo_13 wrote:
Could you please explain the connections and how you apply the signal?
Each pressure transducer has a 4 pin connector.
1&2 are 9-32Vdc supply voltage pins.
3 is a +ve signal output
4 in earth.
1+2 connected to uninterruptible power supply currently set to 10V
3 is connected to ai0 (and ai2 & ai4 respectively)
4 on all three are commoned into the ai9 NI9221 ground connector
05-18-2023 02:29 AM
So it would appear that it's a fault with the the grounding on the NI 9221.
When connected to the supply ground, instead of the NI 9221, the ghosting disappears.