Whether you are an electrician, a hobbyist or an engineer, you are certain to need one tool: a multimeter. The reason why they are so widely used is that they will measure current, voltage, and resistance for you and can work in both AC and DC settings. And since they are so widespread, you are almost guaranteed to find one at any price-point, all the way from $10 to several hundred dollars. And it is a commonly known fact that the more you spend on a multimeter, you will get a better quality, not only in terms of accuracy and features, but also safety. Let’s compare a range of multimeters and determine how much you spend will affect the quality of multimeter you get.
To fulfill this test, I needed a wide range of multimeters at varying pricepoints, and so I put together a collection of four multimeters to test. Ranging from a pocket meter all the way to a professional grade one. Starting with the professional meter, given to me by my grandfather, is older than I am and it can be bought for about $70 on ebay. This blue one is a dt-9205b+ multimeter and costs $17. The other is this Brymen BM235 multimeter, which costs about $90, also branded by the EEVBlog. Finally, I have this pocket multimeter, which also cost about $17. So, in other words, we have two cheap multimeters and two more expensive ones. Anyways, let’s dive into the testing and what you should look for in a multimeter.
The first thing we can immediately see is that the expensive meters have auto ranging, while the other ones make you select your range manually. The auto ranging capability of these meters is certainly very useful, and will make your life far more convenient, especially if you are probing several different voltage ranges, otherwise, you would have to put your probe down to change the range and then continue testing. And if you do get an autoranging multimeter, make sure that it does allow for manual ranging, because you may find yourself in a situation where you want a range that differs from what the multimeter thinks you want. So, when considering buying a multimeter, definetly take this into consideration, but it is not a deal breaker in my opinion even though it is very, very useful.
The next important aspect is accuracy. For this test we will be comparing the DC voltage accuracy, but you should still keep the other accuracies for current and resistance in mind. The two expensive ones have better accuracies, 0.1% and 0.3% respecively. This cheap one has an error of 0.8%, which is quite high compared to the others. And the blue one has a DC error of 0.5%. Also keep in mind the extra error expressed in digits, which can be found as a plus symbol next to the error. This basically means that the last digit may vary either direction by at most that many. So, a meter with a 2 digit error could read anywhere from 89.8 to 90.2 from a 90 volt input. Both of the more expensive multimeters have a digit error of 2 and the cheap ones have a digit error of three. Adjusting to the proper range will reduce the effect that the error has on your measurement. So, depending on your requirements you probably will have to take error into account, especially if you need very precise measurements. However, most projects do not need an extreme level of accuracy so it is possible to get a cheaper meter to start out.
Another important aspect is going into the micro amp and milivolt ranges. These very small ranges are useful for things like analyzing audio signals and measuring the current draw of a large resistor. The pocket meter already doesn’t have a mode to meausre current so that is a big loss. The cheap blue one can sort of measure microamps, but not at all great compared to the ranges of the better meters. So definetly take the minimum ranges your meter can measure into serious consideration.
For accuracte AC measurements, it is very important to have a true RMS multimeter. The reason is that some meters can measure a typical AC waveform, but without using true RMS, they struggle with odd waveforms. Luckily for me, it seems all of my multimeters have true RMS. So look for a multimeter with true RMS capability, even the pocket one had it, although its accuracy had trouble giving a good reading.
Before we get into the safety aspects of these meters, lets just run through a few features that are nice to have but are not necessary. A backlight so that you can see what you are measuring. A bar graph to let you have to advantages of digital and analog at the same time. Continuity tests. And finally a capacitor meter. All of the features I just mentioned are not at all needed and are not deal breakers, just somethings to look out for when buying a new meter.
Now we can dive into a very important part of these multimeters that sets the cheap apart from the quality: safety. Now you can ignore many of these safety features if you find that the most you are doing with your multimeter is reading from you arduino circuit, but if you have any intention of messing with AC mains voltage or high voltages in general then you should really pay attention to this part. The first thing to note is separate sockets for current and voltage. You do not want to be measuing a high voltage then have it short circuit through the current line on the same input. Also, look for alerts that you are plugged into the wrong socket. It may be possible that you accidentally left your meter on current and forgot, so when you go to measure voltage, you have a short circuit. This meter will beep at you when you select the wrong socket type, making sure that you do not forget to change it. On the other hand, the other meter makes no such effort to alert you that you put the probe in the wrong socket.
Let’s open up the meters to look at the fuses inside, if any. Any good meter will have fuses inside, so even if you are just probing an arduino circuit you won’t completely destroy the circuit with an accidental current short. Ceramic fuses should be prefered but glass will work fine if you aren’t messing with mains voltages. But if you are working with higher voltages, it is basically a requirement to use ceramic fuses for both your safety and the safety of the meter itself. And as you can see the better meters have ceramic fuses and the cheap one has glass fuses. As a side note, my grandfather left tinfoil in the fuse slot a couple of decades ago, something to laugh at. Anyways, you should also look at the internal resistors, because sometimes the cheaper ones try to use small resistors when large ones are appropriate. You should definetly prioritize meters with ceramic fuses and if yours doesn’t have them, you should replace them.
Now let’s look at the probes themselves. First, they should be properly insulated at the ends so that you have no chance of touching them while they are live. All of them are good, except for this meter where the metal is completely exposed. The probes should also be durable and rated for high currents and voltages. Again not a problem for 5 volt circuits but still something to take into consideration.
All in all, it really does seem like you get what you pay for. This pocket meter was very good in terms of safety, but lacks features and the accuracy that is required in a meter. I wouldn’t say it is useless, just don’t get it as your first or main meter. This cheap one really lacks a lot of safety features and also has poor accuracy and doesn’t have a microamp range. So, while I wouldn’t buy it again, it was also the meter that got me through the beginning part of my electronics journey. These two more expensive meters, though, are actually really nice to use after using the cheap one before, and I highly recommend it. If you can afford it, definetly go with a newer meter though because the old one is starting to fall apart, but if you need a high quality meter with a tighter budget, definetly go for an older meter. It still works more than well enough for me to consider using it as my main meter.
So if you are still unsure of which meter to get I’d follow this rule: if you are planning to measure or interact with high voltages at all, go ahead and get a better meter. But, if you aren’t, it is up to your choice. The features provided by the better meters really make for a more enjoyable and headache free use. In other words, ask your wallet. Just don’t get something too cheap is all. Remeber, you get what you pay for.
I hope you find this video helpful on selecting a multimeter and wish you good luck on finding one of your own.