Terms and parameters used in the electrical industry are often situational and relative, but there are prevailing conventions that are useful. Resistance testing is one of them.

Resistance is one of the terms used in Ohm’s Law and is extremely significant. Its effective measurement in electrical equipment runs across a staggering twenty powers of 10, from micro- to Tera-Ohms, and beyond.

Measuring low resistance is important since helps to identify resistance elements that have increased above acceptable values, as well as helps to prevent long term damage to existing equipment.

A low resistance measurement can tell you when degradation is happening in an electrical device.  These changes can be caused by a number of things, including temperature change, chemical corrosion, vibration, loss of torque between mating surfaces, fatigue and improper handling.

Today, increasing demands are placed on all aspects of electrical circuitry.  There was a time when the ability to measure 0.01 Ohm was considered acceptable. This no longer holds true in today’s electronic environments.

What tools to use to prevent damage

Low resistance is typically a measurement below 1.000 Ohms. This parameter has an impact on the choice of instrumentation used to measure it. Common multimeters, or VOMs, may measure only to 0.1 Ω.  A really good multimeter may go to 0.001 (a milli-Ohm). But for thoroughly rigorous and reliable low resistance measurement, what is needed is a true low resistance ohmmeter. These instruments are characterized by two parameters: genuinely low resistance down to the micro-Ohm (μΩ) level, and robust test current, to 10 amps being a common value.

Industries that see significant resistance problems, include power generation and distribution companies, chemical plants, refineries, mines, railroads, telecommunications companies, automotive manufacturers and aircraft manufacturers.  These companies need to take frequent readings to ensure they don’t run into equipment failure because of low resistance.

Choosing the right Ohmmeter for your application

It is important to keep in mind, that when choosing an ohmmeter you think about your probe selection.  This can be just as important in the testing process as ease-of-use and accurate results.

High current tests always require secure connections to the item it is working on because high resistance at the contact point can limit the expected level of test current. This can cause a poor signal-to-noise ratio and ultimately produce erratic results. 

Digital Low Resistance Ohmmeters (DLRO) help to prevent long-term damage and wasting of energy. By using a DLRO or a contact resistance ohmmeter, operators can detect where low resistance measurements are present and remedy the situation before it causes a problem.

Don’t forget to test

These crucial test measurements help you to identify resistance elements that have increased above baseline and can help you save on energy costs and damage to the equipment that is being tested. Set up a schedule for when to use your equipment to maintain your system. Preventive maintenance can save you from a system failure if you catch problems during routine testing.

Further information can be found in the Guide to Low Resistance Testing, a free download.