The proper DMM selection improves job performance, but how do you make that selection?
Whether you know them as DMMs, VOMs, multitesters, or multimeters, digital multimeters are essential tools that continue to evolve and crop up on tool belts and workbenches everywhere. There are so many brands and models on the market now it can be difficult to know where to start before purchasing one.
According to an independent study by the Research Department, Inc., millions of multimeters are sold every year in the United States alone. Most are purchased for under $100, but they can be as expensive as $300 or more for a unit with advanced features.
In many ways, DMMs are becoming the tape measure of the new millennium with their rich feature sets, easy-to-use functions, and versatility. With the addition of a couple of accessories like test leads, specialized probes, and adapters, your DMM can turn test-and-measurement cartwheels.
By conducting a cursory bit of product research, comparing prices, and determining where to buy a DMM, you can save time on each job and money in the long run. Consider and answer the following questions before making your purchase.
What tasks will you do? Without asking this basic question, you could end up with a meter that has the wrong features or improper ranges for the tasks at hand. Determine early in the process what you want to do. Then, frame your search along the lines of your specific needs. Will you measure voltage, current, ohms, or a combination of all three? Do you need frequency, temperature, or capacitance?
What environment will you work in?
Do you work in a shop or in the field? Will your meter need to be heavy duty, waterproof, and rugged? Or will you mainly perform delicate, precise measurements indoors?
Is physical size important? Will you keep the meter in a toolbox, on a bench top, or in your pocket?
Do you need true rms voltage for current measurement of circuits with switching power supply loads?
Will you be working in daylight or in a dark electrical closet? Backlit LCDs are mandatory where lights and visibility are low, and for most of maintenance workers that’s pretty frequent.
What transient category do you need? Some models are specifically designed for electronics troubleshooting (Cat, I and II), while others are right for home and automotive use (Cat. I to III). Most likely, you need one rated for industrial use, and that’s typically going to require a Cat. III 600V rating.
Will your meter stay indoors or will you take it outside? Some models incorporate prop-up stands, and others feature holsters designed to withstand most job environments. If your style is tough or rough, a few dollars spent for a meter carrying case or holster to protect your investment is well worth the money.
Do you need a complete kit or will you buy accessories separately? Many suppliers offer complete ranges of test leads, probes, thermocouples, and other devices that extend the functionality of meters. Several companies also have task-related kits that include everything you’ll need to undertake specific measurements. Look for a wide range of accessories for your kind of work. While you may not need every accessory, the fact that a manufacturer offers the full range needed for your kind of work shows an effort to provide for the market you’re in, and that says something about the meter. If the test leads seem cheap, that says something about the meter, too.
What are the factors of after-purchase service and warranties? With many meters and test tools being manufactured in other countries, the basic meter warranty is of primary consideration. Who will repair it? Where will you send it for warranty work? Does the manufacturer offer an on-the-spot replacement program?
What is the calibration policy? If you need annual calibrations, what is the cost and what is the turnaround time?
What is the hidden cost of buying too much meter? DMMs are like any electronics purchase, whether it’s audio equipment or computers. You can spend plenty and get a multi-function, multi-task, and multi-complicated unit with all the fancy bells and whistles. Be aware however, that as the options and features mount, so does the complexity of operating the unit. And then there is the cost of learning to correctly use the extra features, employing the proper measurement protocols that ensure precise measurement. However, don’t let the hidden cost idea discourage you from getting the features you need. If you use those features fairly often, you’ll find they’re well worth the added expense.
Visiting manufacturers’ Web sites and asking other users what they like and don’t like about their meters will help you make a good buying decision. Tackle the process as you would with any tool you depend on for making your living. This is especially important if you’re buying a large number of meters for a department or crew. You’ll improve the bottom line—not because you got a good deal on a meter, but because you got the right tool for the job.
Allen is a Wavetek Meterman product planner, Everett, Wash.