Unwanted Signal During Daytime

[DonTheMagnet]

Hello All,

I have got a PXIe-4303 input module for voltage measurements. My data acquisition system shares AC power with a machine shop that has heavy machineries, such as EDM and CNC. I see a lot of unwanted signals in daytime, when the machine shop is active. Can electrical noise introduced by inductive loads of the machine shop affect the PXIe system's measurement ability? Moreover, will a power conditioner help fix this problem? Any other advice will be greatly appreciated. 

Thanks,

Don

[santo_13]

In reality, the interference from other equipment on AC lines does not significantly impact the power supply of the PXIe chassis rather it can enter through EMI due to unshielded and ground loop issues in your signal wiring to the instrument.

A power conditioner for the input AC supply of the PXIe chassis may not help improve your noise at the input of the instrument. You need to shield and isolate your signal from external noise before it enters the 4303 instrument.

First, figure out what kind of noise enters the signal chain and where, then fix all methods of noise creeping through the signal entering the 4303 instrument.

[Henrik_Volkers]

Know your enemy:

atach a coil (20cm loop, 1-6 windings or what is available) at one input  (magnetic field sensor 🙂 )

 and a 1m unshielded cable ('e-field' antenna 😉 ) on another

, choose highest samplerate , and l have look what your find.  A FFT of the signal usually give good hints on the source.

If you have a scope (higher bandwidth) try it. (I usually start with line trigger)

The 4303 is a high channel count device ... so i assume your setup is prone to (ground) loops (magnetic antenna and noise due to current in the ground)

Use shielded twisted pair cable where possible (CAT6 is nice and cheap)  , connect to ground only on one side, ...

If you disconnect all inputs and replace them with a short (or a 10k resistor)  , do you still see the signals?