I am rigging up a portable test panel, will be using a true-meter APM that will do up to 600 VAC or 600 VDC. I would like to be able to use it to measure typical U.S. 120 VAC or 240 VAC and 480 VAC. Looking for recommendations on how to build a simple economical circuit such that a fuse would blow if input voltage exceeds ~500 VAC or 500 VDC.

For 480 VAC, is that RMS so would peak voltage be 679 V and would that matter or make things more complicated in building a fuse-able circuit that would trip? The sole purpose being I'd rather blow a $1 fuse than my $70 volt meter.

  • \$\begingroup\$ How much current? I've used back to back lnd150's as input protection... good to ~400V, maybe one could put two pair in series? \$\endgroup\$ – George Herold Mar 12 '18 at 16:11
  • \$\begingroup\$ datasheet for apm-volt-apn says the imedance is 1.5 megaohm, so a few milliamps if not microamps. And the max over voltage rating is stated as 800V. \$\endgroup\$ – ron Mar 12 '18 at 16:46
  • \$\begingroup\$ Did you consider ultra rapid cartridge fuses and metal oxide varistors? \$\endgroup\$ – Jeroen3 Mar 12 '18 at 18:58
  • \$\begingroup\$ no i did not, it has been ~20 years since i messed with stuff like this in school \$\endgroup\$ – ron Mar 13 '18 at 15:54

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