Hello Kai,
Thanks very much for such a detailed description you have given me.
Your justification for using the intended circuit also satisfies me.

Now having gone through the description would like to get few things clarified.

Kai said:
Ureed,ss and Ux,ss is just the AC components of this modulation.

Here Ureed,ss and Ux,ss are going to be the difference voltage experienced by the reed, and the point where Ux exists.
Which is going to be a 'DC' voltage of very small value.
So i couldnt get resonable info on why you have said that difference voltage as AC components of this modulation.

Kai Said:
Take the average of several succeeding readings to cancel noise and hum interference.

So i think this would also give the VCR (Variable Contact Resistance).
To do this, can the successive readings be taken by 1)running a for loop in the software part or, 2) should the coil that drives the switch be subjected to some frequency for a short period?

But it also comes to my mind that only for DCR (Dynamic contact Resistance) measurement a suitable frequency would be passed to the coil and hence CR would be measured when the switch operates (known as DCR).
So, i would like to get some useful suggestions on the above mentioned issues (VCR and DCR) in order to proceed further.


Thanking you,
Suresh.