Multi-meter is useful in the tattoo studio

You should become familiar with a digital voltmeter or multimeter.
It is recommended that all tattoo artists own a multi-meter
as it will allow you to troubleshoot a lot of components of your
tattoo machine and power supply. You can test the continuity of
your machine and any wire on the machine with a pretty basic
multi-meter. You can also figure out which lead on your clip cord
is negative or positive by using the multi-meter. If you recall the
section in this text about capacitors, it is important to make sure
your DC current is running in the correct direction in relation to
the capacitor.