Electrical Engineering/Measuring impedance


permanent magnet+electromagnet combination
permanent magnet+elect  
Hi Cleggsan,

Genki desu ka? I hope you have been well. I have, as always, been busy. I have been working on something and I am wondering if you could give me your advice. I have a mechanism consisting of permanent magnet held between two sheets of rubber, with an electromagnet directly underneath. If the electromagnet is switched on, the permanent magnet is repelled and pushed up. The permanent magnet may also be physically pushed down towards the electromagnet where it may actually come into contact with the electromagnet (with the rubber sheet in between of course)
My question is this- as the permanent magnet moves closer to the electromagnet, I am assuming that this will cause a change n the impedance of the electromagnet circuit - is this correct?
I want to incorporate something into the circuit that will let me measure this change. I am going to have a lot of these permanent magnet+electromagnet combinations packed densely together, can you suggest how can this change be measured?

I hope this message finds you well. Almost typhoon season here in Japan. Not looking forward to that, but at least the rice will grow!

Best regards,

Domo, domo.  Doing well thank you.

ONE: If there are other magnet assemblies near by it may effect the influence on the electromagnet more than the change from the permanent magnet being sucked in - unless there are some shielding material helping to isolate the the adjacent coils and fields.

TWO: Yes, there will be an change in electro-dymanics of the coil by virtue of the change in the magnetic field.  Depending upon the proximity of the two magnets the change may be small; even too small to reliably measure.  That is my worry. The greater effect might be at the moment of energizing the electromagnet as that is when a transient condition is activated; it quickly settles to a quiescent state.

The most simple way of measuring is to monitor the current waveform passing through the coil. With an oscilloscope you could instrument it easily and get a visual take on the size of current changes to then determine if it needs an amplifier to bring up the gain to a more detectable level.

Hope this  helps.  

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