Digital multimeters, or DMMs, are among the most commonly used instruments for testing electronic equipment and other circuits. It works well for basic diagnostic purposes, such as finding a fault in a circuit, as well as more complicated measurements. You can use a DMM to troubleshoot home wiring systems, electronic equipment, homemade circuit boards, domestic appliances and for a range of other applications. Since the price range for a multimeter can range anywhere between $10 and $5,000, depending on the tool and its features, it’s important to get the right one for your needs and situation.
Digital versus Analog
DMMs are the most common option for anyone who needs to check a circuit or system, including hobbyists and professionals alike. They provide a range of benefits over old-fashioned analog multimeters, including higher input impedance, limited reading types and poor adjustability. Plus, since DMMs have become the default choice, it’s getting difficult to find a well-built analog meter. Most of the options currently on the market simply won’t get the job done well.
There are many different brands of multimeter available, including Fluke, Agilent, Tenma, UEI, Blue Point/Snap On and Modis. For occasional use, store brand DMMS may work out well, but most serious users require a better quality device. Fluke multimeters are considered the industry standard and have an accordingly high price, but many enthusiasts favor them for their durability and reliable readings.
Factors to Consider
No matter which multimeter brand you choose, there are several basic factors to consider before you buy. While it’s tempting to simply purchase the most advanced multimeter you can afford, that may not actually be the smartest choice. You need to stop and think about how you’re most likely to use the meter and what kind of readings you need to take. Then look at the meter’s resolution, accuracy and calculation options.
Resolution is a term that refers to the minimum measurement size possible for a given device. In most digital multimeters, this is expressed in digits and counts. Meters are often rated as 3 ½ or 4 ½ digit devices, indicating that they can display three or four numbers from one to nine, followed by a single digit that is listed as 1 or a blank. On a basic 3 ½ digit meter, you can see up to almost 2,000 counts of resolution, but advanced designs can bring that as high as 6,000 counts. If you don’t need to measure very tiny values or very large amounts of power, you should be able to purchase a lower-count meter.
Accuracy is also very important. It indicates the largest acceptable error for your meter, usually expressed as a percentage of the reading. For the majority of users, an accuracy reading of about 1% should be adequate, but specialized projects may require a lower margin of error. Since you’ll pay more for higher accuracy, it’s important to decide whether you’ll need the 0.5% error ratio of the Fluke-117 before you purchase a device of this quality. A highly inaccurate meter, however, will do little more than tell you whether or not your circuit is working.
Another big factor in your DMM purchase could be durability. If you mostly use your meter at home, you may not need one with an extremely sturdy build. If you plan to take your equipment outdoors or travel with it frequently, however, you’ll need to look at a unit that offers some degree of physical durability. Many are available with tough rubberised cases that are highly recommended, since they’ll protect your DMM from falls, something that’s bound to happen eventually.
No matter what circuits you need to test, you can’t go far without an appropriate multimeter. Take the time to do your research before you buy!
Written by: Joining a phone company straight from school, Tony Mullins’s experience was initially all on the job but as his family got ever better at breaking electronics, his skills improved and he got new areas of expertise. His children may be relying on his skills to repair things too much; they bought him a Fluke-117 for his birthday.