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Electrical

What is an Isolation Test?

By G. Wiesen
Updated May 17, 2024
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An isolation test can be a number of different possible tests, and the context and industry in which the term is used will typically indicate the precise meaning of the term. In general, this type of test is used to isolate one part of a device, machine, or electrical system from the larger system in order to determine where a flaw or issue exists within the system. In engineering, for example, this type of test is usually performed in any type of system in which a current flows, regardless of whether the current is gaseous, liquid, or electrical. An isolation test will usually be used to disengage one part of the system from the source of the current, battery or pump, and then test that part for flaws.

In an electrical system an isolation test could be performed to find where a signal or current was being lost. If a computer is not turning on properly when it should be doing so, for example, then this type of testing is usually performed to find the problem. Another computer system that is working properly will usually be used to assist in performing an isolation test on various parts of the computer.

The isolation test may begin with the power supply being removed from the nonworking computer and then installed within the functioning computer. This isolates the power supply in order to test it within an otherwise functioning system. If the functioning computer no longer turns on, then the fault is likely to be with the power supply.

On the other hand, if the system works properly, then other individual aspects of the malfunctioning system will then be subsequently isolated and tested further. Each cable running from the power supply to other components, for example, can be tested individually. By removing other components, an isolation test can also be run on the motherboard, random access memory (RAM), central processing unit (CPU), and other parts of the computer.

A similar type of isolation test can be performed on other types of systems and devices as well. If reduced pressure is found within a system in which water or air is being pumped through a number of different tubes, each tube can be removed and isolated from the system, then tested to determine where the pressure is being lost. Of course, numerous problems could also exist, so an isolation test may often be performed on each part of a system, even after a single flaw or issue is located.

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Discussion Comments

By miriam98 — On Aug 03, 2011

@NathanG - I worked in software support for many years. You learn to be really good at process isolation in order to troubleshoot people’s technical problems (and no, rebooting the computer doesn’t fix every problem).

I had a checklist of things that I would walk the user through, testing a piece of the software at a time, to figure out where the glitch was.

You learn the software yourself pretty well in the process, and more importantly, you develop your deductive reasoning skills. You become a detective of sorts, using strategic, targeted tests to find out why the software is not working properly.

By NathanG — On Aug 02, 2011

@allenJo - We did isolation testing in the software industry. We have something called unit testing. This works in applications that are built in modules, a piece at a time.

With unit testing we test a specific module and see that it runs correctly. We get back results or error messages, just like you would with an engineering application – or in your case, an automobile.

As applications get bigger and bigger, unit testing becomes more important. It’s nearly impossible to figure out what can go wrong with an application simply by testing the whole application in one fell swoop. There are just too many pieces to the puzzle.

By allenJo — On Aug 01, 2011

My check engine light came on once, and I went to the auto parts store to have them read the codes. It came back with a code that indicated a catalytic system efficiency error.

The guy at the store told me that this was an error code that told me the general location of the error, but didn’t isolate the specific component. I was hoping it wasn’t the catalytic converter.

I took it to the mechanic, and he did the isolation testing. First he checked the exhaust in the back for leaks. That was okay. Then he checked the oxygen sensors. They were okay.

Finally, he checked the catalytic converter. Sure enough, that was the problem; I needed a new one, and it wasn’t cheap either. Only isolation testing could have pinpointed the problem.

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