There are few people who need the different functions of a multimeter more than HVAC technicians. HVAC professionals can use a digital multimeter to diagnose problems, gauge performance and, with the right model, temperature. Even when the ability to read temperatures isn’t a requirement, it’s a great feature to have that will make life a lot easier when you’re trying to work with HVAC appliances.
In this blog post, we’ll show you what to look for in a digital multimeter when you’re planning to apply it to HVAC appliances, and which features will make the biggest difference. Most of these features can be found on a lot of digital multimeters.
Features your digital multimeter must have to work with HVAC appliances:
- Voltage meter
While you’ll be hard pressed to find a digital multimeter that doesn’t measure voltage, your HVAC multimeter should be able to measure AC voltage up to 600V and DC voltage up to 300V. It is also important that your DC voltage can be measured in 1 mV increments. For the best performance, make sure that your multimeter is CAT-III certified.
- Amperage meter
Where the voltage meter measures the capacity of your electrical circuit, the amperage meter measures the bandwidth that’s actually being used. Your multimeter should measure AC Amps up to 300A. The smallest measurement should be at least 1/100A.
- Resistance meter
Resistance is measured in Ohms and can tell you how well a circuit or component is performing. The Ohms meter is displayed with a Ω symbol on your multimeter. Make sure your multimeter can at least measure up to 5 MΩ (that’s 5 megaohms) in increments of 1/10 Ω.
- Continuity meter
The continuity test is used to see if an electrical circuit is closed or open. This is another feature that is probably present on almost any digital multimeter you can buy, but make sure yours has this feature. The continuity test should come with a beep.
For the smaller A measurements, make sure your digital multimeter can read as little as 1/10 of a microamp. Convert amp to microamp here: Measurement unit conversion
- Capacitance tests
A common problem in HVAC compressors is a failure of the hard-start capacitor, which results in a breaker trip. Making sure your multimeter can test for capacitance will help you make sure you can properly diagnose these problems.
The above features are a necessity in using a digital multimeter in an HVAC environment. The features below are therefore not necessary, but they will save you a ton of time and effort, and are worth it if you plan to use it more than once:
This seems too easy to be, true, but a lot of HVAC appliances are tucked away in dark corners or crawl spaces. Even if there is a light in the room, chances are you’re still working in the shadows or dark corners. Having a screen with a backlight prevents you from running into problems with reading your test results.
- A temperature probe
Even if it’s not included in your multimeter, you’re probably finding a way around this by carrying some sort of external thermometer. But if you can have a multimeter that includes temperature probes, it will save you space, time, and effort.
- Auto-ranging features
The fanciest multimeters can automatically detect where on the scale your measurement is taking place. If you know what range you’re working with, this may not be as big of a deal, but otherwise the auto-ranging feature can save you a lot of time.
- A True-RMS meter
A True-RMS meter will allow you to read distorted or non-sine waves. This is especially handy in bigger appliances with high voltage, such as HVAC appliances.
- Detecting ghost voltage
It’d be nice if you could rely on your reading and not wonder if you’ve got a false positive. Some multimeters come with the ability to detect ghost voltage and thereby eliminating these false positives.
While it seems like a long list of features to pack into one multimeter, there are some multimeters that pack all these features into a hand-held meter. Some manufacturers even designed digital multimeters specifically with HVAC technicians in mind. The model that comes to mind first is the Fluke 116. Not only is this a Fluke and therefore the best quality digital multimeter you can buy, it has all the features listed above.
The Fluke 116 is also competitively priced because it was designed as part of a series that created great quality products while also using cost-cutting measures that keep the prices of the multimeters in the series as low as possible. The durability and engineering quality of the Fluke 116 is beyond anything that competitors can offer. If you’re planning to spend a lot of time around HVAC appliances and equipment, it will be the only multimeter you’ll need.