🚀 go-pugleaf

Nathan Stewart was worried about frying his multimeter while working around
tube circuits with typical 350V - 500V plate supplies.

Not to worry, guy.  PROVIDED THAT YOUR MULTIMETER has an appropriate voltage
range, you are not gonna draw enough current to hurt it.  The typical DVM
has an input resistance of around 10 Megohms.  The typical old-style VOM
used a 50 uA meter movement (20,000 ohms/volt) and the internal voltage
dividers were sized to allow the meter to draw that current at full-scale
voltage.  If you hit the meter with a higher voltage than the current
range, you can hurt it, which is why MODERN DVMs say OUCH when their input
protection circuits clamp.

The usual problem is that your meter draws enough current from the circuit
to throw it off.  You usually won't see this, unless you are working on something
REALLY touchy.  (I had a couple of megohms in series with a big electrolytic
capacitor a few years ago: I was trying to observe RC time constant in action.
With a 20,000 ohm/volt meter, on a 3V scale, I was effectively shunting my
capacitor with a 60K resistor.  Made a nice voltage divider.  I bought a DVM
that day, right after I realized what I was doing wrong.)