The Ultimate Guide To Using A Multimeter
If you’ve just purchased a multimeter and aren’t quite sure what you’re going to do with it yet, we’ve arranged a handy guide for you here to make sure that you can get the most out of its various functions. We’ll also be discussing some basic safety to prevent you from getting hurt or burning up your meter while you’re working, but with a little bit of practice with a multimeter you’ll rapidly learn how to operate your multimeter like a pro.
Safety
The first thing to keep in mind with any useful tool is, of course, safety. While a multimeter might not have rapidly moving blades or belts to rip off fingers, without a bit of precaution you can certainly end up experiencing electrical shock or damaging your meter.
You’ll need to keep in mind the meter’s safety ratings in order to know what range you’ll be able to operate your meter in. These are usually one of the first listed specifications on your meter and you’ll need to keep them in mind, especially if you often find yourself dealing with high voltage. The ratings are measured as CAT-I to CAT-IV with a secondary rating to show how much transient voltage they’ll be able to handle. Almost all multi-meters will at least have a CAT-III rating, but you’ll want to make absolutely sure if you’re going to be using it for anything but small, low-voltage electronics.
You’ll also want to make sure that you’re not in direct contact with the metallic ends of your probes, electricity takes the easiest way “downhill” in all cases and causing yourself to become the ground of a high voltage system can range from merely painful to the absolute last thing you experience depending on a variety of factors.
The other major concern is the amperage of a circuit, most malfunctions that result in meltdown or damage to the meter and user come from high amperage. While most high-end models will have a cut-off or fuse, you’ll want to be able to rapidly drop the probes from their contact just in case. In the event anything weird starts happening with your meter, immediately remove the probes, this is easier with touch style probes than alligator clamps, so keep that in mind when deciding which leads to use for the job – though most meters will only come with one set of leads.
In any case, it is extremely important that you read the manual that came with your tool. Not every tool is the same, and one you’ve used in the past may have slightly different functionality to the one you’ve purchased. Reading the manual should also provide additional valuable safety advice if you’re unfamiliar with them.
Measuring Voltage with Your Multimeter
Measuring voltage is likely to be one of the most common things you do with your meter. The basic way that a multimeter functions is by causing the current to flow through the meter to allow for measurements, and usage for reading volts is a rather simple affair.
The first thing you’ll want to do is power on your meter and set it the appropriate range. Some meters may have an autoranging ability as well, but even these will usually allow you to select the proper range for what you’re doing. DC voltage will typically be designated with a V next to a straight line on a multimeter’s dial and AC voltage with a V next to a squiggly line. Make sure that you set the device to the proper reading and range, and you’re ready to begin.
After you’ve selected it using the dial, take note of where your points of contact (points you’ll be measuring between) are. On most circuits the points of contact are easily identifiable by having a black mark or the letter N for a neutral or 0 volts, and a red mark or the letters A or L for the active. Once you’ve identified your points of contact simply take your black probe and hold it on the neutral/0 volts point, then take your red test probe and hold it on the active point. The reading should appear on the LCD panel of a digital multimeter rather quickly, high end models like a Fluke 87-V will read much more quickly than a lower quality one.
By doing this you’ll be able to tell if a piece is functioning or exactly how much voltage the part of a board you’re checking is taking, which will allow you to base your repair or further modification upon.
Double check your range before you take any further action, especially if you’re new to using one of these tools.
A quick and easy test to perform, to get a feel for measuring voltage, is to measure the voltage in a AA battery. First set your meter to DC volts, then as we discussed above, you simply hold the black lead of your meter to the bottom of a battery (the flat end of the battery), then place the red lead to the top of the battery. If the battery is new and fully charged, your meter will read 1.5 volts.
Measuring Current with Your Multimeter
There’s two main methods to measure current using your meter, one of which is quite simple and the other of which is more complex.
If you have a clamp-style amp reader on your meter the whole affair is rather simple, once you’ve set your meter’s dial to amperage all you’ll need to do is place the clamp over the line and read the meter. Most people who work in the field will want one of these, as it greatly simplifies matters.
Your meter can still read current without one however. In this case you’ll almost certainly want alligator style clamps, as doing this with regular test probes can be a bit cumbersome although it’s still possible.
Some systems will have test leads specifically for this purpose, in which case you’ll be able to rapidly get your reading without having to do a whole lot of extra work. Unfortunately, quite often the work will be on you, and you’ll need to break the circuit in a place where you can make your multimeter a part of it with your probes. It is extremely important that the power is turned off before breaking the circuit.
Once you’ve carefully broken the circuit, use your clamps to fulfill the broken part of it through your meter, then turn the power back on. If you’ve set it to amperage you’ll soon enough have the information you’ll need to continue after you’ve re-affixed the wires or contacts you’ve opened to allow for your reading.
Measuring Resistance with your Multimeter
The other primary and often vital function available on virtually any multimeter is the ability to measure resistance. This is another quite simple affair, and the first thing you’ll want to do is set your meter to the ohms setting, for those unfamiliar with it the setting will be marked as Ω on your dial. Some meters will offer a range for ohms as well as voltage, so select the appropriate one if this is the case.
As a precaution it is generally advisable to only measure resistance when the part is not directly connected to the circuit, so you may wish to power down the unit or break the circuit in whatever way you can before taking your reading.
After this you’ll simply apply the probes to two contact points and take your reading, giving you the knowledge you need to continue further with your project or repair.
Testing Continuity With Your Multimeter
First check that your multimeter is able to test for continuity, the continuity setting will usually be pair with another setting on your multimeter, most likely the resistance setting and will have a symbol that looks like so ( 
).
Next, de-energize the circuit you wish to test and place the test probes across the two points on which you wish to test.
Your meter will emit a small buzz or tone when it detects continuity (a complete path) between two points – hence why it is also referred to “buzzing a circuit”.
Conclusion And A Final Word On Safety
Once you’re comfortable with using your meter, it is vital that you test that your meter is working correctly before you use it each time. It would be pointless and potentially highly dangerous if you were to test a live circuit with a faulty or flat meter, then thinking it was safe to work after the meter had displayed an incorrect reading.
To test that your meter is working correctly, you simply follow the instructions from above, but on a source that you know the voltage of. The quickest and simplest way is to test the voltage of a standard power socket that you know is in good working order. If your meter is charged and working correctly, it will read around 120v for the USA and Canada, and 230v for the UK. If you do not know the standard voltage for your country, you can find it out easily by searching “your country standard voltage”.
This guide should be able to get you started on using your multimeter efficiently, safely and making the measurements you need. If you’re completely new to taking electrical measurements you may want to read up a bit further on electricity in general, but with a good, functional multimeter in your hands and a bit of knowledge you’ll soon find yourself able to fix almost any electrical problem. Remember to take all the precautions necessary to proceed, and pretty soon all of this will be second nature.
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