To Test or To Measure

Hello readers
This caused my thought circuits to fail and it is a 'simple' question
I am told (from an exam). So what do you think - I thought it total
nonsense but hey who am I?
For the following 'electrical' quantities - state whether you would
either test OR measure them:
supply voltage
insulation resistance
load current
earth fault loop impedance
I'd 'measure' them all, so didn't get the question - unless test meant
just to test something was present e.g. supply voltage present.
Any views.
BB
Reply to
Badbetty
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Two of them are undefined or very loosely defined and depend on specific situations and conditions and may have values of extreme range. The other two are simple numbers that can be precisely and easily measured. Which do you think is which?
The way to get at this is to ask yourself how would I measure each of the four parameters? The answer is trivial for two of them, not so easy for the other two.
Reply to
Bob Eld
Being picky, I would suggest that "test" in this context implies a go-no go result based on a published standard/specification.
So you may easily just want to "test" supply voltage, insulation resistance and loop impedance as all have laid-down limits. These tests would be the sort of thing that you might expect for mechanic/technician level workers as there is no expertise or judgement expected of them. Their test equipment may easily just have a pass/fail indicator.
Load current, OTOH, doesn't have a "universal" specification. No piece of general purpose pass/fail test equipment could be made - so a measurement has to be made.
There are exceptions - eg portable equipment with long leads may be permitted to have a higher loop impedance. For such equipment, exceptionally, a measurement would have to be taken.
So, I would say that, in the general case, load current would be measured and the rest tested. However, there will be many exceptions to the latter, where a measurement is required.
-- Sue
Reply to
Palindrome
Well, the question does seem rather bogus.
But I would say that supply voltage and load current are conditions of operating, so you 'measure' to find out the values.
Insulation resistance and earth impedance aren't 'measured' while the system is operating, you have to shut it down and then rig up a 'test apparatus'. Something like a meggar for example to measure the insulation resistance. So those are 'tested'.
But that's rather vague and one could argue about ways to 'measure' those parameters even when operating, so I'd throw the question out.
Personally I hate test questions that rely on you remembering one person's (the instructor's) pet definitions and conventions. Same thing with some textbooks. They act like "This is how it's done in the industry, so remember it!" Like one not-so-hot teacher I had years ago that swore 'electric current' always flows from positive to negative. As proof, he showed us all the 'hand-rules' about current flow and magnetics. When someone (ahem....) pointed out that you could turn everything around, use opposite 'hand rules' and negative to positive electron flow and get the same answers, I thought he was going to have a stroke :-)
daestrom
Reply to
daestrom

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