Filtering in Noisy AI Circuit

[diarmaede]

Hi All,

I am using an NI-9205 Compact DAQ module to monitor multiple pressure lines.  I have the pressure transducers connected to the DAQ module via more that 50' of unshielded cable per line.  There are a couple noisy components in the test fixture, a heat strip with an automatic on/off function and a sparking ignitor.  Both of these items are causing large amounts of offset in my pressure readings.

I am going to order shielded cable right away, and I am going to wire them to cut my cable lengths down to ~20' each.  Is there anything else I should do to shield the transducers from the noise?  Do I need to connect the cable shield to ground on both sides of the cable?  Sorry to be such a gumby here, but as you can see, I am far from an EE.

Thanks in advance for your help.

- FB

[AnalogKid2DigitalMan · Accepted solution]

Use shielded twisted pair, ground the shield at one end only. Using a differential analog input configuration can reduce the effects of external noise too.

Keep the signal cable away from others if possible, if it crosses paths of other 'noisy' cables, cross at 90 degrees where they intersect.

Using shielded cabling for the heater and sparker or even grounded metallic conduit can't hurt either, if feasible.

EDIT: Refer to this white paper:

https://www.ni.com/en/shop/data-acquisition/measurement-fundamentals/field-wiring-and-noise-consider...

-AK2DM