Save Your Meter

Any multimeter, when set on current, becomes a low resistance. If you accidentally put the probes across a supply, it shorts out the supply!

Let’s go over the reason that the meter is low resistance on amps. To measure current, the meter must go in series with the part or wire that is carrying the current. You have to open up a place to stick in the meter. This is usually bothersome to do, so we don’t measure current very often, we prefer measuring voltage across a resistor and calculate the current.

Better meters have a fuse to protect you if you mistakenly let a lot of current through on the amps setting. Industrial technicians are sometimes killed by accidentally having their meter on amps when they intend to measure 220 volts or 600 volts.

Warning—do not clip-lead your probes into a circuit, intending to measure voltage, then sweep the selector dial across amps or mA on your way to volts.

A tricky thing about "in-circuit" measurements—for ohms or capacitance measuring, the meter is probably confused by "parallel paths," including semiconductor junctions.