Try the analog memory trick with CMOS gates or an opamp. The floating
capacitor can hold charge for a minute or more if care is taken. By care I
mean that the charge/discharge paths are to be buffered with a suitable
bipolar trz. connected such that it does not leak when the power is off.
The CMOS sense input can be connected through a very large value R like
4.7M (this is whay it has to be CMOS).

Peter

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