I have an HP200CD that needs some loving care. The manual says to measure
the difference in the voltage between two different points in the circuit --
it shouldn't be all that much but the voltages between these points and
ground is in the hundreds of volts range. The manual also says that I
should be using a meter with 220M ohm or greater input impedance to make the
voltage measurements. Any suggestions where such a beast could be
bought/rented/stolen?

TIA
Norm