Best Grounding Scheme For Pwm Electromagnet, Pwm electromagnet digital/analog signals

[fernandomierhicks]

Hi:

I have a setup were I run a electromagnet with a PWM signal using 20 volts, usually at low dutycyles < 20%. PWM frequency in the low kHz range.

Around this electromagnet I have various sensors, cirucits etc.All of this (electromagnet and circuits) is inside a metal chamber (faraday Cage). I need to run some signals outside this chamber, analogue and digital.

The power supplies for the Electromagnet and the other circuitry are ground-isolated.

I want to reduce the noise that the Electromagnet is going to produce on my signals both because of the pulsing and the EM interference.

I was thinking of using coaxial cables for all my signals, using a star scheme once the wires are inside the chamber, so I will have a dedicated ground wire.

Should I also use coaxial cable for the electromagnet leads? Should I ground the shield on this wire to my general "signal ground"?

Should I ground both ends of my signal wires shield?, lets say to the frame?

Any other suggestion recommendation is appreciated, wire types are flexible.

Thanks

Fernando

 

[(*steve*)]

If you use coaxial cable, I think the best bet is to connect the coax shield to the cage where it enters/exits.

On the other hand, you *may* be able to get away with a simple twisted pair.

If your signal level is reasonably high, and the impedance low, you will obviously have less problems than in the reverse case. Understanding the signals is key.