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Is This Thing On? How to Use a Multimeter

- October 23, 2017 by Dan Heinen, ASP (View all posts by Dan)

Disclaimer: I’m not an electrician, I hate working with electric. I’m the type of person that will turn the main breaker to my house off if I have to rewire an outlet or replace a light fixture. The spark of a screwdriver from crossing circuits, to shaking your hand cursing while jumping about because you touched the black and white wires, to the sound of sirens as medical personnel  arrive are several ways to verify that the circuit you thought was off, really wasn’t. Here, I’ll provide a general overview on how to verify power using multimeters.


Used to test for live power, multimeters are also known as amp meters and occasionally voltmeters (although the two are different). There are quite a few on the market with a wide range of capabilities. Most can be either analog or digital. The difference in those two is just the display.

So, how do you know if it will do the job you need? How do you know whether you have a reputable one or not?  Here are several things to think about if you are going to purchase a multimeter:

USE- What will it be used for? How high will the amperage and/or current will it need to measure. Multimeters have designated categories. A simple line of thought is the higher the category the high it’s capacity to measure current and amperage.


  • CAT I – used for specialty circuits such as signal levels special equipment and low-voltage equipment.
  • CAT II – More typical of household or local level 120v-220v outlet junction boxes standard wall outlet or plugs and single phase equipment.
  • CAT III – Hardwired equipment, fixed stationary motors bus bars three-phase equipment, service lines, and distribution panels.
  • CAT IV – Utility level and origin of installation outside underground and overhead lines.

Is it a quality meter? Independent testing most of us are familiar with is the UL label. We see that on just about everything buy. This means an independent testing agency has tested and verified that it can, will and does what it says it is able to. But, if it does not have the UL label, does that mean it is no good? Not always. There are several testing labs out there look for, UL, CSA, TUV or other approved labs. An item can only be labeled if it has passed their quality standards. If it is labeled CE it means it has met the European Commission requirements. Manufacturing companies can self certify with a CE mark; therefore, units with a CE mark do not have to be tested by an independent testing group. Beware of such wording “Designed to meet specifications of…” Remember, the Titanic was “designed” to be unsinkable.

When choosing a meter, remember you are relying on it to keep you safe, so chose wisely.