Hook ammeter to switch without turning off main circuit

I'm building a NIXIE tube clock in a Soviet Steampunk theme, and I've got an old Soviet era voltmeter and ammeter for it. Because they are pretty old I don't want them on all the time, just when I press a test button (one for each meter) on the front panel. I'll probably wire a couple of old Soviet panel lights (with modern LED bulbs) in to light up when the meters are active. The voltmeter isn't a problem. But since the ammeter has to be wired in series with the clock PCB, if I turn it off it will turn off the clock too. So how can I wire the ammeter (0-3 A DC) so it's on a switch that doesn't affect the clock? Will I have to use a CT on a switch or is there some other way? The whole thing runs on a 12 vDC, 500 milliamp power supply.


by shsavage
February 24, 2022

2 Answers

Answer by shsavage

Do you mean like this?

+2 votes
by shsavage
February 24, 2022

Yes, exactly like that. Press the button to take a current reading; release it and it drops to 0.

by OakBloodThree
February 25, 2022


by shsavage
February 25, 2022

Answer by OakBloodThree

To turn off the ammeter, use a normally closed switch that shorts it out.

+1 vote
by OakBloodThree
February 24, 2022

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