Digital Multimeters: One size does not fit all

One size does not fit all. Selection of the proper multimeter involves significant consideration. Cost is one, another is the specific purpose of the device. How it will be used and the qualifications of those using it are also important. The author...


Did you ever see a television commercial advertising a new universal wrench, which claims to be the replacement for all the open end, box, and adjustable wrenches currently in your toolbox? I can honestly say that enticing as the product appeared, there was no doubt in my mind that it would not provide the mechanical assistance needed to remove the retaining nut on a Falcon 50 windshield heat terminal strip. There were a few other tasks that came to mind where this universal wonder would not be my tool of choice.

On the other hand, I did see some areas where it could be of value. The same is true when it comes to the use of multimeters. There is not really any one device that will fulfill all the needs. Yeah, I have a toolbox with all the required hand tools. I also have a tool bag containing electrical testers. Five of which are multimeters, no, they are not all the same. Why five? Well if being an aircraft electrician with the last name of Sparks is not qualification enough, then it is because I have discovered over the years that one size does not fit all situations.

Tool Selection: What to Consider

Selection of the proper multimeter involves significant consideration. One concern is often cost. Just because you go out and spend hundreds of dollars does not always mean you get what you really need to do the job.

For me, the most important factor in selecting a multimeter is the specific purpose of the device. Will I be working in confined spaces where ambient light may be a factor? What about the ability of the unit to be supported in some condition other than flat on its back? How about switching functions when in a tight and blind location? Does it have an audible tone? If the use involves testing systems for either return to service or validation of operation, having an ongoing program to ensure calibration is essential. Available local support may be an issue if other than name brand equipment is used. Where it will be used and what will it be measuring are two significant concerns.

Just because another common name for a multimeter is a VOM (short for volt ohm meter) does not necessarily indicate that this is all the device can be used to measure.

How will it be used and what are the qualifications of those using it, may be other things to consider. The more functions that a device can accomplish oftentimes can make the appearance more intimidating to the inexperienced user. Frequently in general aviation it becomes necessary for a technician to determine if a light bulb is intact or verify continuity in a wire, fuse, or other electrical component. Testing a malfunctioning circuit for applied voltage is another common occurrence. If this is the primary reason for having an electrical tester, then a very basic unit may fit the bill.

Size in and of itself is often a factor and in part can be a consideration in the environment where the device is to be used as well as storage space. In a previous professional life I worked as a technical representative for an airframe manufacturer and had the opportunity to travel the world, often at a moment's notice, and had to assist operators by providing troubleshooting assistance. I have a small 1¼… by 3…” basic meter that would easily fit in a carry-on bag. This device was very inexpensive so if it were ever confiscated or lost, replacement would not be a big problem.

Know the Current Requirement

Analog or digital can be another factor in deciding on the best tool for a job. As a rule a digital meter will not impose a significant load on a circuit while it is operating. An analog meter on the other hand requires a certain amount of electrical current flow through the meter movement in order to produce a noticeable deflection of the pointer. In fact analog meter movements are rated in ohms per volt which will provide a reference to how much electrical current is needed to drive the needle.

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