Getting a Multimeter for repair
One of the most versatile tools for repairs is the venerable multimeter. As the name implies, it can measure (-meter) several (multi-) different things. Most of which are required to find faults. You can use it to measure batteries, cables that should work and many more things.
What is it
A multimeter is a device which can be used to measure voltage, resistance, continuity and several other things. It can help you understand the state of an electronic device and help you find faults. Most of the multimeters you can find are battery powered and come in a rugged case. It is one of the things you never know you need and once you have one, you can’t imagine living without it.
What do you use it for
The most prominent use for a multimeter is to measure voltages. Is the battery still ok or is it dead? Does my radio no longer work because the power brick is dead or is the fault in the radio? Many such questions can be answered with a quick voltage measurement.
If the light on your bike does not work, you can measure the so called continuity. With this mode you can “see” whether the wire is broken somewhere or not.
If you are building a light for your dollhouse with a LED, you can measure whether you have it installed the right way.
These are only a few examples of things you can do with a multimeter. I always have one beside me on my workbench and use it all the time.
What do you need
Now that you are persuaded that you need one, you will notice that there are hundreds of different multimeters to choose from. To picture above shows you two quite different options. The multimeters to the left cost 20$, the one to the right 500$.
To keep it short, if you do not intend to measure voltages higher than about 50V (which you shouldn’t anyway when you learn something from this post) you can buy one of the cheapest multimeter you can find.
There are some differences in usability but all the cheap ones do enough for initial low voltage repairs.
How to choose one
If you do not want to buy the first multimeter you find on ebay, here are some things you could look out for. Most of them are present in a device such as the Aneng 8008 which you can see to the left in the first picture.
Autorange is a very useful features. This means, that you do not have to choose the correct range of the unit you would like to measure. On the cheap multimeter in the picture, you have to select whether you want to measure below 20V, 200V etc. all the others in the picture just have a position Volt and they select the range automatically.
A continuity checker that beeps is almost a must in my eyes (the very cheap one in the picture above doesn’t have one). And a FAST continuity checker ist very handy. When set to continuity mode, the multimetter will beep as soon as there is contact between the two probes. This can be almost immediate (good) or sluggish (bad). This behavior can often not be seen from the listing in an online shop, but you can search for a test of the multimeter you want on youtube and the tester will certainly test this.
Some (very) cheap multimeters have rather stiff cables. This is very annoying. If you pull a little on a cable when measuring, your multimeter can topple over. Take one with softer leads and if you’re at it, check that they are removable.
The best way is to have a look at some of the multimeter tests on youtube.
Safety notes
As I noted above, don’t measure anything above 50V with your cheap multimeter. This means, do not stick it into a mains plug and do not work on devices which are directly connected to mains. If there is a AC adapter that supplies your device, you should be safe (but read the voltage on the label just to be safe).
A cheap multimeter will not immediately harm you if you plug it into mains. It will probably even show the correct voltage. BUT: In some unwanted situations they can explode or give you an electric shock. A lot of the higher price of more expensive multimeters goes into safety features. Do NOT believe the rating labels on cheap multimeters (e.g. 1000V Cat II), they are wrong!
Conclusion
A multimeter is a very useful tool and can be had for little money. It is an invaluable tool for any electronic repair. Its use is not hard, but has to be learned and needs some practice. My seven year old daughter can use it already to measure batteries and check whether she needs to charge them.
It takes time to understand all the functions of this measuring device and many of them are rarely used. I will write the different things you can measure in the future. Just stay away from high(er) voltages unless you are confident about what you are doing.
