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Level Sensor Output Signal: 240-30Ω, Is it possible to measure with PXIe 4300?

Hello,

 

We have an electrical motor that we run at roughly 50HZ which creates signal interference with several sensors we have connected to our DAQ systems whenever the motor is turned on. 

 

Is there anything that can be done to reduce this interference? The motor is controlled by a controller which are connected via a shielded cable, and all of the instruments are grounded and connected using a shielded cable as well. 

 

Thank you!

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The first thing to do is a documentation of all(!) wires and and contacts (grounding) you have in your setup.

Start with the power lines on one side and work to the other side to the DUT.

Mark ground connections you can't change (savety, (stupid desingned) sensors that connect power supply to GND/housing,...)  

Collect all datasheets ...

 

 

Motor SPSUs are prone to create EMI. A filter between SPSU and motor can help, together with a grounding strategy (central, depending where the ground currents flow...)

Electric motors create (and work withSmiley Wink ) magnetic fields, you can't shield with copper. Reduce wire loops, use twisted pair cables, route the cables crossing less magnetic field lines and finally use IRON to shield (change mag field lines).

 

Greetings from Germany
Henrik

LV since v3.1

“ground” is a convenient fantasy

'˙˙˙˙uıɐƃɐ lɐıp puɐ °06 ǝuoɥd ɹnoʎ uɹnʇ ǝsɐǝld 'ʎɹɐuıƃɐɯı sı pǝlɐıp ǝʌɐɥ noʎ ɹǝqɯnu ǝɥʇ'


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Hey mjed,

 

I think Henrik_Volkers provided some great next steps. I just wanted to provide you with some documentation to read over that might help make the wiring of your system better or how to deal with the noise if the wiring cannot be helped.

 

Field Wiring and Noise Considerations for Analog Signals

http://www.ni.com/white-paper/3344/en/

 

Five Tips to Reduce Measurement Noise

http://www.ni.com/newsletter/50262/en/

 

Working with LabVIEW Filtering VIs and the LabVIEW Digital Filter Design Toolkit VIs

http://www.ni.com/white-paper/4851/en/

 

Hope these help!

Gerald M.
Applications Engineer
National Instruments
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