In addition to the measurement symbols, one symbol you must always be aware of when using a multimeter is the Ground (GND) ...

we came across this interesting wideband AC millivoltmeter circuit from 1990. The design featured 12 ranges, decent accuracy, 200 µV accuracy, and a frequency range from 20 Hz to more than 2 MHz.

You can use a schematic diagram, a multimeter, or a visual inspection to find out the type, polarity, voltage, and current of each power source. You should also check if there are any switches ...