I plan to permanently mount a multimeter in a circuit to measure current.

  1. Since the multimeter is put in series in the circuit, will the circuit be open if the multimeter is turned off?

  2. The print on the multimeter states "5 A max, unfused, max 10 sec every 15 min". Since the current is around 350 mA, it only generates about (0.35/5)^2 < 0.5% of the max allowed power, can I leave the multimeter permanently in series?

  • \$\begingroup\$ No and yes......The multimeter has something along the line to measure current but it doesn't open anything when powered off (let's just say for argument sakes it's a very small resistor that it measures the voltage across to determine current) so current can still flow. \$\endgroup\$
    – DKNguyen
    Feb 28, 2021 at 5:04
  • \$\begingroup\$ I had a digital meter once that DID open the circuit when power was turned off. So they exist, but yes most do not open the circuit. \$\endgroup\$
    – Kyle B
    Feb 28, 2021 at 17:09

1 Answer 1

  1. No, the circuit will not open when you turn off the meter.
  2. Yes, you can leave it in series without damaging the shunt as long as your ambient temperature is such that the shunt resistor can dissipate enough heat to prevent damage or fire.

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