Page 6 - February 2023 Track N Times

TECHNICAL TRAINING

Ring It Out …...By Jason Canty, Field Safety Specialist

The Ohmmeter and Megohmmeter.

A little background regarding the term “ring-out”. This term is from the “olden days” when multimeters were
rather expensive and delicate pieces of equipment. Back then, workers would use a simple low voltage device
having a bell that would ring when a “continuous” circuit was found. This verified correct point to point wiring of
harnesses etc. referenced to schematics or pull charts.
The Ohmmeter works in a similar fashion by supplying a low voltage signal to a circuit under test and reading the
voltage drop between the leads. Components inside the meter convert this into the familiar “Ohm’s” value and is
displayed on the screen.
Safety First! Be certain no Power is applied to the circuit/device you are
testing, and that all appropriate Lock Out Tag Out procedures are fol-
lowed.
Most multimeters have built-in protection, but it is not safe to take resistance
measurements on a live circuit, and any readings would be invalid.

To use the Ohmmeter function on your “Fluke” select the “Ohms” position and
connect the leads to circuit you wish to test.

The “Continuity” function.
With this feature, a beep or tone will sound if the measurement is below 25
Ohms. You can access this by selecting “Ohms” and pressing the yellow function
button.
To check the continuity of wires over a long distance, a length of wire can be
used to extend your meter’s leads. The wire provides a known reference. Any
size or length can be used, just factor in the added resistance (if any) of the test
wire.

Devices:

Ohmmeters can test parts such as relay and solenoid coils. 24V relay and solenoid coils should show a relatively
low resistance of 25-300 ohms. Higher voltage coils usually have higher resistance readings. In most cases, a
reading of approximately 500 ohms or less is acceptable. Fuses should be checked with an ohmmeter because
they can look good, but still be bad. A good fuse will read near-zero ohms, a bad fuse will have a very high or

“OL” display reading.
Devices:

Ohmmeters can test parts such as relay and solenoid coils. 24V relay and solenoid coils should show a relatively
low resistance of 25-300 ohms. Higher voltage coils usually have higher resistance readings. In most cases, a
reading of approximately 500 ohms or less is acceptable. Fuses should be checked with an ohmmeter because
they can look good, but still be bad. A good fuse will read near-zero ohms, a bad fuse will have a very high or
“OL” display reading.

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VOLUME 4 : ISSUE 1