From the question it should be clear I'm no expert. Just want to learn.

I have a digital multimeter.

If I connect the multimeter to hot+ground & hot+neutral on the 240v 50hz (max ~30A) AC wall outlet to get an AC voltage reading, is it safe to do so on the input fused for 250mA? The 10A input doesn't allow voltage readings.

And if I connect the 10A input will it be safe to measure the amperage of the wall outlet? I've already used the 10A input to successfully measure DC current of a 12V 1.25A power adapter, and the 250mA input to measure the voltage of the same device.

Current, in amps, is basically provided based on demand right? So I'm thinking the multimeter won't demand much to measure voltage (microamps) so it won't blow the 250mA fuse? Then when I switch to Amp Mode connected to 10A input it won't demand more than 10A to give a reading, correct?

Please excuse me if I've said anything totally incorrect. I'm an electronics novice just trying to learn the fundamentals.


  • 2
    \$\begingroup\$ Do not try to measure current by inserting the multimeter to the wall socket in the amp setting, this will create a massive short. \$\endgroup\$
    – S.s.
    Commented Dec 8, 2018 at 2:18
  • \$\begingroup\$ I just remembered the warning about this! You have to use in series with a circuit. Okay I won't be doing that part. How come the volt setting won't create a short circuit? \$\endgroup\$ Commented Dec 8, 2018 at 2:23
  • 7
    \$\begingroup\$ If you don't understand why measuring current can create a short circuit while measuring voltage does not, you should not be fooling around with wall outlets. You need to do some studying about the fundamentals of electricity so that you are familiar with the meanings of voltage, current and resistance as a minimum. \$\endgroup\$
    – Barry
    Commented Dec 8, 2018 at 2:56
  • \$\begingroup\$ Which multimeter do you have? Does it have a cat rating on it? \$\endgroup\$
    – Passerby
    Commented Dec 8, 2018 at 3:13
  • \$\begingroup\$ It's a TACKLIFE DM02A, CAT-II rated according to the manual \$\endgroup\$ Commented Dec 8, 2018 at 3:15

1 Answer 1


Yes it is generally safe to use a multimeter to check the voltage on a wall outlet, but use caution on cheaper meters.

The meter will be employing a high resistance when on voltmeter mode (1 MOhm to 100 MOhm), so little actual current will flow.[1]

However, on ammeter mode, the meter will be employing very low resistance[2] and will cause a short circuit if connected to both live and neutral or ground[3]. It would also be very unsafe to touch due to the very high current. In the UK, wall outlets generally supply ~30Amps[4]

When I plugged my meter, on AC voltmeter mode, into an outlet's live and neutral, as well as live and ground, both times I received a reading of 239V on the screen. I did not test on ammeter mode as I did not have a proper circuit to test with in series.

Thank you all for your comments on my original post. Things weren't making sense to me until I wrote here and had your feedback.


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