A device that anyone tinkering with electricity and electronics must have is a VOM, or ‘Volt-Ohm Meter’.

You can buy one, or you can build one.

Then you can measure voltage and resistance. More sophisticated ones can measure also inductance, capacitance, frequency, diode voltages, transistor gain, and all kinds of other things. Some can even plug into a computer.

Naturally, as is true of most test equipment, you get what you pay for. You can buy a cheap one, but it’s not going to be very good, and you can buy a good one, but it’s not going to be very cheap.

This has led to hobbyists with more time than money trying to build one, one that is better than the cheap ones and cheaper than the good ones. Some of these hobbyists really do know what they’re doing, and sometimes they see a little success, but by and large it’s far more hassle than it’s worth. They run through endless trials, tribulations, and trouble.

I’d recommend you buy one.

You see, it is not an easy thing to make your meter.