Vibration Transducer connection

[maypot]

For some make of vibration transducers, the cable screen is connected to the instrument earth (0V) at the monitor end and not connected to anything at the transducer end to avoid earth loops if the machine earth is at a different potential, that is the positive and negative wires are insulated from ground and the screen is isolated within the transducer.
For some few,the screen is connected to the body of the transducer.
What are the pros and cons of each ?

Bob

 

[GregLocock]

I used to work in a noise and vibration lab, with 12 channels of accelerometers. If I noticed that the data was getting noisy at mains frequency the second port of call was to change the earthing inside the charge amps. This was a switch that coupled the signal earth to casing earth.

I'd say that flicking the switch helped >75% of the time.





Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[itsmoked]

maypot; it is hard to say one is better than the other. As GregLocock said sometimes one is better than the other. Thermocouples are notoriously grounded to their sheaths. In my applications this generally worked fine as long as the instrument end was not connected.

It probably has a lot to do with which end has the quietest inherent earth.

 

[djs]

There is a theory that the shield should be grounded at the input or receiver end. The reason being that the shield is at ground with respect to the input and therefore less common mode voltage is induced into the signal wires.

 

[GregLocock]

yes, that's the theory. The people who designed my amps know what they are doing, that's why they put a switch in.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.