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Encyclopedia of Electrical Engineering
 realnfo.com
Encyclopedia of Electrical Engineering

# Ohmmeter

Ohmmeter is an instrument for measuring electrical resistance, which is expressed in ohms.
The ohmmeter is used to perform the following tasks and several other useful functions:
• 1. Measure the resistance of individual or combined elements.
• 2. Detect open-circuit (high-resistance) and short-circuit (lower-resistance) situations.
• 3. Check the continuity of network connections and identify wires of a multilead cable.
• 4. Test some semiconductor (electronic) devices.
Fig.no.1: (a) Measuring the resistance of a single element. (b) Checking the continuity of a connection. (c) Identifying the leads of a multi-lead cable.
In general, the resistance of a resistor can be measured by simply connecting the two leads of the meter across the resistor, as shown in Fig.no.1(a). There is no need to be concerned about which lead goes on which end; the result is the same in either case since resistors offer the same resistance to the flow of charge (current) in either direction.
When measuring the resistance of a single resistor, it is usually best to remove the resistor from the network before making the measurement. If this is difficult or impossible, at least one end of the resistor must not be connected to the network, otherwise the reading may include the effects of the other elements of the system.