[Radio Wrangler]

Many valve voltmeters have resistive range attenuators before the first valve, and so have finite loading resistance on the circuit being tested.

The same goes for transistorised meters.

With modern DMVs there is usually a need to arrange the input range attenuation to allow autorange switching with the electronic switchhes at conveniently low voltages. This usually means having the attenuators designed with constant input resistance, not maximum input resistance.

This is a design style thing, not a valve versus semiconductor thing.

Oh, there is a technique using matched varactor diodes measured with oscillators that allows voltage measurement with only the DC leakave of a reverse biased diode and a couple of capacitors. Solid state electrometers can be made this way.

David