Uses for An Ohmmeter

Ohmmeters measure electrical resistance in ohms and were developed by the German physicist Georg Ohm, of whom which the device is named. Ohm discovered that the flow of electric current through a conductor was directly proportional to the potential difference (voltage) and inversely proportional to the resistance to current flow. This amount of resistance to the flow of current is measured in ohms.

The Types of Ohmmeters

Ohmmeters come in two basic types: analog and digital. They both perform the same functions of measuring voltage, current and resistance.

Analog ohmmeters use a battery to apply voltage to a resistance. The amount of current is indicated by a pointer attached to the galvanometer which registers the amount of current on a scale measured in ohms.

A digital ohmmeter can tend to be more accurate. It uses an electronic circuit to pass a constant current through the resistance while a separate circuit measures the voltage across the resistance.

What Type of Ohmmeter Do I Need?

Whether to use analog versus digital ohmmeters depends on the user and the intended purpose. If you are considering purchasing an ohmmeter to pursue a hobby then only a basic digital model may be necessary. For design engineers, professional technicians, or electricians, you may require a far more expensive unit.

An ohmmeter can be used to troubleshoot many household items. A ceramic fuse for instance, which may offer no visible means to determine if it's blown or not, can be tested with an ohmmeter. If an ohmmeter indicates a short circuit then the fuse is good. An open circuit indication means it's blown. Stereo cables, speaker coils, guitar pickups and other electrical devices can be tested and verified with an ohmmeter.

Things to Remember:

There are several considerations to keep in mind when using the multimeter to measure resistance, or ohms. If using an analog ohmmeter to measure ohms, the meter must be zeroed. This means you must short the test leads together and use the zero control to set the indicator needle to zero resistance. This must be done each time the range is changed. With a digital ohmmeter there is no need to zero the meter.

Whether using an analog or digital ohmmeter always make sure there is no power applied to the circuit under test to prevent possible damage.