Look for these features when buying a multimeter

Multimeters can be handy for troubleshooting PC power problems. But the range of features and prices can be confusing when you're shopping for one. Before you waste time and money, find out which features are essential and which are merely nice to have.

With a multimeter, a support tech can troubleshoot everything from PC power supplies to coaxial networks. Depending on the features included, multimeters range in price from under $20 to several hundred dollars. So before you go and spend a lot of money on a multimeter, you should know which features are important and how to compare those features. Follow my tips on buying a multimeter and save yourself some time and money.

Current, continuity, and a whole lot more
When many people think of multimeters, they think of devices that measure current or continuity. In the old days, this was true. However, newer multimeters perform many more tests. When looking for a multimeter, you should first identify the type of testing you will need it to perform and the anticipated tolerance range for those tests.

For example, most multimeters measure electrical current. When considering a multimeter, it's important to know how much current you will need it to read and how much current it can actually read. If you have a multimeter that reads 120-volt AC current, you would probably kill yourself if you tried to measure a thousand-volt power source with it. Likewise, a multimeter for testing 120-volt AC current would be useless for testing a 12-volt DC power supply inside a computer.

Measuring voltage
Most multimeters allow you to select an appropriate voltage range before conducting any sort of test. In Figure A, you can see that the multimeter I’m using has a dial you can use to select functions. Each function is divided into ranges. For example, in the V AC (volts AC) section in the lower-left part of the dial, you can select 2 volts, 20 volts, 200 volts, or 600 volts. Each of these are maximum values, so if you needed to measure a 120-volt power source, then you’d choose the 200-volt range.

Figure A
The lower-left portion of the dial allows you to select AC voltage ranges.

Directly above the V AC section is a V DC section. Having the ability to measure DC voltage is important when working with computers. Inside the case, the DC voltage levels range from 3.3 volts to 12 volts.

Measuring ohms
Another important feature is the ability to measure ohms, which is basically the same as measuring resistance. A support tech might need to measure ohms to check continuity. For example, if a switch is open or a wire is broken, then no current can pass through and resistance is infinite. If, on the other hand, a switch is closed or a wire is good, then there will be very little resistance and current will be able to flow freely.

Of course, using a multimeter’s ohms reading isn’t the only way to test continuity. You can spend a lot less money on a multimeter if it simply has a continuity test rather than being able to measure ohms. However, I personally recommend spending a few extra bucks on one that can read ohms because by measuring ohms, you can test network and SCSI terminators. You may have noticed terminators classified by their number of ohms (i.e., a 50-ohm terminator).

Remember these important features
From a computer standpoint, the most important features to look for in a multimeter are:
  • The ability to select a range of voltages
  • The ability to measure AC and DC voltages
  • The ability to measure ohms

There are other features that are handy but not necessary. For example, although not every multimeter has it, my multimeter comes with a temperature probe. I’ve found this to be an extremely useful feature for working with PCs. A multiprocessor can do some really strange things when it overheats, and the temperature probe allows you to determine exactly how hot the processor is or to measure the temperature inside the case.

Additional features, such as the ability to measure AC and DC amperage and to test capacitors and transistors are nice, but they are seldom used when working with computers. My multimeter was a midrange model that cost about $100. It does everything that I need it to do and isn’t as difficult to use as some of the higher-end models.