A valve power supply has two outputs, V1 is 700Vdc and V2 is 450Vdc.
I want to switch a 300mA ammeter between the two without interrupting either supply.
I attempted to use relays to switch the ammeter in and out of either circuit, but the switching action causes a supply interruption.
I now want to put a low value resistor, say 1ohm, in series with each supply and then use the 300mA meter as a voltmeter to measure the voltage across the resistor. This way I can switch the meter between the two supplies without interrupting either.
The voltmeter should have its own supply (say 12V which is available) for the 300mA meter.
The reason for wanting to use the 300mA meter (and complicating the issue) is because its what I have on hand (old style antique) and I have already cut the hole in the chassis for it. Oh dear.