On Mon, 16 Nov 2020 19:59:42 +0000, Andy Burns wrote:

It has no means of measuring the voltage

isn't it powered from a wall-wart?

It is.

if that is a straight transformer type with internal regulator, it would
have a scaled-down voltage reference

But judging by it's size and weight its not got much iron in it...

--
Cheers
Dave.