If you put a 10M resistor in series, and use a 1.2V source (actually, a
1.5V battery would work fine), you'll get 200mV when the resistance is 2M, and about 23mV when it's at 200k ohms. That sounds about right.However, your digital panel meter may have a low resistance itself, thus messing with the reading. Hopefully, it will have a 10M or higher resistance, so it won't interfere too much. If it interferes too much, come back and somebody will help you build a buffer to measure the voltage with.
HOwever, I think this circuit will be fine. Use courier font, or other monospaced font to view.
10MEG ___ + .--|___|---o------o Probe1 | | | | | | | / \ Meter 1.5V --- (_/_) - \_/ | | - '----------o------o Probe2(created by AACircuit v1.28 beta 10/06/04
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If you need to power the meter, use separate batteries.