More specifically, THIS voltmeter, which is a little bit "under-spec'ed", to say the least: Radio Shack (22-223) https://www.google.de/search?q=radio-shack+22-223&tbm=isch It's set to the 10V-AC range. I'd expect a VC backed company to invest in a little more elaborate measurement equipment than that.
On the other hand, given a a good RMS meter operated in a frequency range where it's spec'ed to work and a knowncircuitimpedance will give you a very good measurement of the power: P=Vrms²/R. And analog meters make for rather pretty demos, to be honest.
On the other hand, given a a good RMS meter operated in a frequency range where it's spec'ed to work and a known circuit impedance will give you a very good measurement of the power: P=Vrms²/R. And analog meters make for rather pretty demos, to be honest.