Is measuring 220v AC current from wall socket with multimeter safe?

Question

I've purchased a cheap Aneng multimeter (model SZ08). Since I'm not an expert in electronics, I have some questions related to the usage of this device. For instance, I wonder if measuring 220v AC current from wall socket (as the seller shows in his video on aliexpress (photo) ) actually safe? Won't the probes overheat?

Answer 1

It is safe if you are aware of what you are doing.

The probes won't overheat when used within the ranges specified.

Don't touch the metal parts of the probes when they are in contact with live wires - or any wire until you are sure it is not live.

I measure mains voltages with my DMMs all the time - what they are designed for, BUT I have bought one Fluke meter and another AVO meter which are both good quality.

There are some cheap meters around that I would hesitate to use on anything over 50V...

Answer 2

There are several hazards to be aware of.

• Probes overheating? The probes, like the current input on the meter, are good for the rated 10 amps. The meter is reading 1.6 amps, so there is plenty of margin in hand.
• Mains voltage on the meter? The probes appear to be well constructed, so touching the plastic of the probes, or the meter, should be safe. We can expect transients of up to 1500 V from mains. However, any plastic insulation that's thick enough to support itself mechanically can handle that voltage. The other 4mm connections on the meter will be potentially live as well, do not touch them or connect leads to them while measuring mains current.
• Measuring mains voltage with the meter? That is unsafe, whatever the CAT rating on the meter suggests. I strongly doubt whether the voltage dropping components in the meter are rated for the full expected 1500 V transients. The failure mode (very rare, but very possible) would go like this. A high voltage mains transient breaks the input voltage-dropping resistor, causing it to arc. An arc is a short circuit, so the input fuse of the meter would expected to open to handle this. I strongly doubt whether the small fuse on the meter input is properly rated to handle mains, so might fail to open, causing a full fault current to flow through the leads and meter. We are now relying on the house distribution box to open a fuse or breaker to protect the wiring, which it may or may not do, given that its expected protection current would be well above the 10 A rating of the probe leads, possibly 20 or 30 A. I will see if I can find a link to what can happen if you measure mains voltage with an under-rated meter (explosion, technician killed, distribution cabinet demolished).