Selecting an Ohmmeter on Amazon.com
An ohm meter, also called an ohmmeter or ohmeter, is a testing device that measures any electrical resistance to the current flowing through an electrical circuit or component. Electrical resistance slows the current passing through a conductor. Electricians use ohm meters to diagnose problems in electrical wiring to help determine the cause of a component or circuit failure. An ohm meter is commonly used to test motors, generators, cables, switchgear, distribution networks, components, and appliances.
Available as benchtop or handheld models, ohm meters display resistance measurements in either analog (with an indicator needle) or digital form, measured in ohm (Ω) units. Ohm meters may have more than one range for testing resistance, such as 0 to 2,000 megohms and 0 to 400 kilohms. Digital ohm meters may have an auto-range feature to help ensure accuracy when measuring resistance within a specified range. An ohm meter may have multiple test voltages for spot and step voltage testing.
A micro ohmmeter (or microhmmeter) and a milliohmmeter are two types of low resistance ohmmeter. They measure small electrical resistance values in ranges such as 0.1 microohms to 30 kilohms or 10 microhms to 4 kilohms. A megohmmeter, also called an insulation tester or megaohmmeter, measures large electrical resistance values in megohms. This type of ohm meter commonly tests DC output current, DC output voltage, test time, current leakage rate, and resistance range values of cables, cable reels, wires, electrical motors, and transformers, and is also used to test insulation resistance (IR) with high-voltage, low-current electrical signals.
Considerations when choosing an ohm meter include the range of resistance to be measured, and the resolution and accuracy required for the application. Other features of ohm meters include comparator functions for setting high and low thresholds, the ability to output data to a PC for analysis and documentation, and four-wire resistance measurement capability for improved accuracy over two-wire measurement methods.