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AC current measurement question

  1. Mar 8, 2008 #1
    Please excuse my rather dim question but I'm very familiar with homebrewing all manner of DC powered circuits but when it comes to AC..I'm in the dark, sorry.

    I'm building a firing circuit for oilfield perforating. We will have AC (Generator) so I'm using a variac to slowly build-up voltage to fire the cap/pcord.
    I have a AC voltmeter downstream of variac and have an AC ammeter but I've been told that you can't wire it in the circuit in series as you would in a DC circuit???
    It is an old simpson panel meter and I'd like to wire it in but I don't want to fry it accidently.

    My wiring sequence is:
    AC>switch>variac>switch(safety)>voltmeter>cable to well

    Does this make sense?
  2. jcsd
  3. Mar 9, 2008 #2


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    It depends on the meter. Some have an internal shunt and can be connected directly (in series of course), some require an external shunt. If yours requires the latter, it will indeed fry without it.

  4. Mar 9, 2008 #3
    Thanks moo,
    I didn't know a shunt was applicable in AC current measurement.
    I'll see if I can find a part # on meter and google some.
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