I have a complicated digital multimeter and a tiny analog one and a cheap new digital that gives weird high readings, I don't trust it.
I understand how to use one for automotive parts and that's about it.
the good quality one has 2 adjusting dials.
there are 6 settings
30 MΩ 10A
Then the second dial
I checked with settings of 3 and AC mA
The other setting AC V doesn't seem right (open circuit)
Using a sears analog tester set at V AC 50 it moves slightly about .2 volts
and about .1 volts in the small tanks.
In a glass of water zero.
Looks like there is measurable current from all electrical items and living creatures.
Some heaters put out too much and lights do too.