Is electrostatic instruments measure ac and dc?

I don't quite understand what you mean... :( I know the Van de Graaff generator producing static electricity...

I did a search and found electrometer, also called an electrostatic voltmeter. It can therefore measure the voltage.

Here's a link:

Electrometer - Wikipedia, the free encyclopedia

I don't understand, either. But, electrostatic implies positive and negative poles and that implies DC only.