Toolipedia: Everything you wanted to know about multimeters
What is a multimeter?
A multimeter, alsoknown as a volt-ohm-milliammeter (or VOM), is a device that measuresvoltage, current(amps),resistance,and continuity. Multimeters are used byelectricians, auto mechanics, HVAC professionals andothertechnicianswhosejob it is totroubleshootelectrical andelectronic equipment.The multimeter was invented by a British post office engineer named DonaldMacadie whowas tired of carrying around several instrumentstotroubleshoottelecommunicationcircuits. These are the common partsof a multi-meter:
- Test lead jacks/ports
- Test leads
How is a multimeter used?
The black test lead always stays in the COM Port. The red test lead will get moved from one jack to anotherdepending on they type of meter you have and what you are testing:voltage, current (amps), resistance,orcontinuity. The dial is set tothe type of current you are testing for (A/C or DC)and the range of thevolts or ampsyou will be working with. Checkthis storyout for moredetailedinstructions on working with multimeters. Electricity is inherently dangerous, soalways refer to the manualfor instructions/warningsfor yourspecificmultimeter.
What are the different types of multimeters?
In addition to digital multimeters,there areanalog multimetersthat havea physicalscale and aneedle/pointer.Only asmallnumber of analog multimeters are still being madecompared to digitalmeters.Clamping multimetersaredistinguishableby the clamp on the top that resembles apincer. The otherdifferenceswill mainly be found in the range of voltage and amps that can be measured andaccuracy.A low-end multimeter can be bought for $10, while a super-accurate laboratory version will cost thousands.The bells and whistlealso vary from one multimeter to another. Somemeters are combined withinfraredimagingcameras.
What makes a good multimeter?
- Easy-to-read displayandlabels
- Large buttons anddials that can be operated while wearing gloves
- Backlit screen
- Quality carrying case
- Clamp for easy current measurements
- Auto shut-off
- Hold button to record the highest and lowest readings
For the most accurate readings, hold the probe tip points (not the sides) tightly to a contact. Avoid touching the metal tips with your fingers. Your body could act as a circuit and influence a reading (and get you zapped!).