In message , Jeff Liebermann
writes



One problem with the thermocouple ammeter. It's slow.

The other problem with the thermocouple ammeter is that it's easy to
burn out the thermocouple.

If you come across one in a sale, before you part with your money first
twist the meter enthusiastically from side to side, and note how the
needle swings. It should be reluctant to move - ie it's well damped by
the almost short circuit of the thermocouple. If it swings freely, it
almost certainly means that the thermocouple is open-circuit.

But if you've been unfortunate to buy a duffer, don't totally despair.
With a simple internal rewire, at least you'll have a usable* 500uA or
1mA FSD moving coil meter.
*Convert to diode type?

.




--
Ian