How can I measure the voltage in a stand alone motor start capacitor with ratings of 440 volts @ 60 uF avoiding destroying the DVM? We were given a formula for determining the power in a cap, but were not told how to measure the capacitor without changing the out the caps conditions or blowing up the multimeter?

  • 1
    \$\begingroup\$ What in the world sort of DMM are you trying to do this with? One of those Horror Fright ones? \$\endgroup\$ Commented Oct 22, 2017 at 22:49

1 Answer 1


Motor start capacitors are only used on AC motors and there will be an AC voltage across it.

  • To measure the voltage across the capacitor use a multimeter or voltmeter with a 1000 V safety rating.
  • Switch the meter to the next AC range higher than 440 V.
  • Connect the probes safely to the capacitor with the power switched off.
  • Stand back, switch on, take the readings and switch off before disconnecting.

Do not try this with a $5 meter. Both meter and probes need to be adequately rated with a recognised safety mark.

  • \$\begingroup\$ No ac this is DC and start caps exist out side of motors and ac circuits thanks though I have a friend who has a pile of DVM'S. From measuring caps .I just was trying to get a head of the problem .jim \$\endgroup\$ Commented Oct 24, 2017 at 6:28
  • \$\begingroup\$ What sort of 440 V DC motor uses a start capacitor? Please put all the information in the question. \$\endgroup\$
    – Transistor
    Commented Oct 24, 2017 at 7:08

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.