Digital Multimeters



Posted: Tuesday, January 03, 2006

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Digital Multimeters Only a few decades ago, if you knew how to use a multimeter, you were probably an electronics technician or an engineer. But, today, the handy test equipment known as a Digital Multimeter should be in the toolbox of every handyperson. The multimeter is great for determining the working status of many appliances. Multimeters are available in either digital or analog models. Digital multimeters will display readings in numbers. Analog multimeters indicate the value with a needle over a scale. A basic digital multimeter is available for as little as $8.00 and up, depending on your test requirements.

Have you ever wondered why a light doesn’t turn-on. If the lightbulb is not bad, the lamp may be out of order? Is the lamp cord bad? Here is one simple example where a digital multimeter comes in very handy. A useful function of a multimeter is the resistance, or “continuity" test function. To avoid the chance of electrical shock, it is important to never use the continuity test function on any appliance that has live voltage connected. Always make sure the appliance is first NOT connected to any power source.

Now with the power disconnected, set the multimeter dial to Resistance (Ohms). Touch the two test probes together (one is Red “positive", the other is Black “negative"). The OHM meter reading will indicate zero resistance. When there is zero resistance, you have continuity. A reading of zero indicates the circuit is closed and the circuit can conduct current. Now for an easy first test, take a standard lightbulb out of a lamp socket. Touch one test probe to the bottom of the lightbulb, and touch the other test probe to the threaded side of the lightbulb socket. If you read continuity, or zero resistance, the lightbulb is good. If the meter does not indicate continuity, then you know the lightbulb interior filament is broken (current can not pass thru). The same test can be performed on two ends of a simple electrical cord. If the meter does not indicate continuity, then there is a break in the circuit, and the cord is probably cut. Remember to never test the continuity of any cord or appliance with the power on. Always first disconnect any power or current source.

To test a switch, place a test probe on each side (pole) of the switch. When you move the switch from the off to on position, the multimeter reading should change from zero to infinity. If not, then the switch is not working properly. To test a motor, touch a test probe to each pole. Again, a reading of zero indicates that the motor has continuity, current can pass through, and the motor windings are good.

After carefully studying the instructions of the digital multimeter, you will be able to move on to more detailed electrical tests. A multimeter can measure alternating current (AC or household current) or direct current (DC or battery current) in a live circuit. It can also check voltage. A multimeter can test 120 volts AC in a home circuit, or it can test DC batteries to learn if they are weak or fully charged.

Take the time now to learn how to properly use a basic multimeter. You will be glad you did when someday you would like to verify the cause of an everyday electrical problem.

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Top-level comments on this article: (2 total)
» left by Anonymous 2 years 344 days ago.
Mostly yes. I now know that a 0.00 reading means 0 resistance. Would like to know what it means when the meter, when set for reading continuity, does something else, such as cycling through a bunch of numbers.
» left by Anonymous 2 years 147 days ago.
I have a Craftsman Digital Multimeter. It has 7 Ohm positions 20m 2000k 200k 20k 2000(->+) 200 and the last one looks like pipes under the kitchen sink. None show zero when switch is off (except the pipes that are always zero). The first six show 1 on far left of digital display with switch off. Can you tell me what position is for continuity. Is 1 the same as zero. What should infinity read (I don't think the digital display has a symbol)?
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