Weird extension lead test results?

[JohnW2]

https://www.jprelec.co.uk/pdffiles/uni_t_ut528_pat_tester_user_manual.pdf
Page 16. ... Although as per some other things, it does not conform exactly to what the manual says.

I still don't fully understand. I presume that you are referring to ...

so, I presume ....

(1) if Polarity is correct (obviously implying that both L & N conductors have continuity) it displays "√ Good"
(2) if polarity is reversed (again implying that both L & N conductors have continuity) it displays "x Cross"
(3) if one or both of the (L & N) conductors is open circuit (no continuity), it displays "x Open"

... but it says that it also checks for a "short circuit", and from what you've said, it sounds as if that may have resulted in it displaying something like "x short" - is that correct? However, after you 'pressed the button' it will already have done the IR test (before the 'Polarity' one), which I think you said your lead 'passed' - did it display "√ Riso", indicating a IR of at least 2 MΩ? However, I see no indication of what that IR test is of - is it L-N or (L+N)-E, I wonder? If the former, then we're back to the question of how on earth it can be declaring a (assumed L-N) "short circuit" if the L-N resistance is ≥2MΩ.

Do I take it that you did the following (it doesn't say what it actually does, electrically) ...

The manual is certainly 'deficient'!

Kind Regards, John

 

[mattylad]

Assume what you want, your correct about the deficiency of the manual.
Your guess is as good as anyone's lol

 

[JohnW2]

Assume what you want, your correct about the deficiency of the manual. Your guess is as good as anyone's lol

Indeed.

I think I would say that this machine (together with it's manual) is not just intended to be "idiot-proof", but is also "expert-proof". I can't see how anyone, no matter how extensive their knowledge and experience of things electrical, could be comfortable putting their name to the result of a 'testing' it had been used to undertake. The most they could really 'certify' would be that they had "pressed the machine's button and then it displayed 'Pass' (or 'Fail')", without any clear understanding of what the machine had actually done - and 'the cleaner' could have done that.

As I implied in post #5, way back on page 1, I would not be at all surprised if there is actually absolutely nothing wrong with the cable you tested.

Kind Regards, John

 

[plugwash]

Well there is a list of what it is supposed to be testing in the manual, but the failure message the user reports doesn't seem to match up with any of the tests in the manual.

BTW I notice from the manual that the tester has a "long lead mode" and says it is for leads "up to 30m", were you using said mode. If not that could well explain a failure.

I agree these "idiot box" pat testers are not a good choice, A tester should tell you what it's measuring so you can compare it to what is expected for the device in question.

On the subject of Uni-t, I bought (well got my employer to buy) a Tenma (Farnell group own brand) insulation tester a while back that appeared* to be a re-branded uni-t and while I found it usable for what I needed it for after I figured out it's quirks I found it's behavior on low resistances to be potentially misleading. I notice said meter has now been replaced by a new version, I wonder if the new one is better.

* The box had a logo in one corner that looked like uni-t's logo but in a different color.........

 

[JohnW2]

Well there is a list of what it is supposed to be testing in the manual, but the failure message the user reports doesn't seem to match up with any of the tests in the manual.

Quite - although the lead testing section (p16) does indicate that the 'Polarity test' includes a test for "short circuit" - so I imagine that relates to the "short" failure message matty said he got - even though the manual does include that one in the displays it describes (I suspect it's meant to be "x Short").

However, as I've previously implied, there are at least two crucial things that (unless I'm missing them) the manual does not appear to be telling us. Firstly, as regards this poorly-documented 'short circuit' test, is it talking about an L-N 'short' (I presume it is) and, if so, what is the (numerical) criterion for failing this test? Secondly, what is tested for the 'Insulation test' - L-N, (L+N)-E or what?

Those things are crucial because, since we've been told that the cable passed the IR test (which the manual says means ≥2MΩ) then if that's a N-E resistance measurement, then it would clearly could not also be a N-L 'short circuit' by any credible definition - so, if that were the situation, I see no alternative to the machine being faulty (or, at least, behaving incorrectly). Indeed, even if it's not N-L that is being IRd, we still need to know the nature and pass/fail criteria of the 'short circuit test', since matty's other measurements do not seem to be compatible with anything that could sensibly be called a 'short circuit'.

BTW I notice from the manual that the tester has a "long lead mode" and says it is for leads "up to 30m", were you using said mode. If not that could well explain a failure.

Indeed - as you will have seen, I've already asked matty if he pressed that button. As I also said, we are not told what happens (electrically) if one does use that mode and, if we did, it might give us some insight into what the machine is actually doing/testing!

I agree these "idiot box" pat testers are not a good choice, A tester should tell you what it's measuring so you can compare it to what is expected for the device in question.

Exactly. And (again this is not meant to be any criticism of matty!), any such instrument, in any field, which is designed to be usable even by someone who hasn't any idea about what the tests mean, how/why they are done and how to interpret results (if only it gave actual 'results'!) is, in my opinion, extremely unwise.

I suppose we're getting close to a point (or maybe have already got there) at which it would theoretically (technologically) be possible for an airline to employ totally untrained pilots (maybe recruited from the cleaning staff), and to have planes whose 'flight decks' had nothing other than a series of buttons labelled "Press to fly to New York", 'Press to fly to Sydney" etc. - but I don't think that you'd find me as a passenger on such a flight

Kind Regards, John

 

[SUNRAY]

I suppose we're getting close to a point (or maybe have already got there) at which it would theoretically (technologically) be possible for an airline to employ totally untrained pilots (maybe recruited from the cleaning staff), and to have planes whose 'flight decks' had nothing other than a series of buttons labelled "Press to fly to New York", 'Press to fly to Sydney" etc. - but I don't think that you'd find me as a passenger on such a flight

Kind Regards, John

How would you know, the cockpit door are now locked and reinforced?

Getting back to PAT'ing within BT and your raised point about recruiting from cleaning staff. As I mentioned we had to construct our own tester, after a short while our boss decided the testing within our 7 exchanges was too expensive for the engineering staff so he 'trained' one of the cleaners [lovely divorcee who I dated briefly] to use the machine, check fuse rating and rewire plugs. Initially he didn't provide any tools so she was always borrowing from us and it was quicker for us to open the plug and check/repair than keep going to find our tools. Eventually she had her own wallet tool No.3 and basic tools including Hellerman pliers [for the ends of fabric covered cables]. Sadly she created more faults than what she fixed and it turned out she was colour blind which cleaners weren't checked for but engineering staff were.

 

[Gasguru]

So we have the cheapest PAT on the market from a manufacturer with a hopeless reputation and it gives dubious results...what else would you expect?

 

[JohnW2]

So we have the cheapest PAT on the market from a manufacturer with a hopeless reputation and it gives dubious results...what else would you expect?

Indeed. Even though my suggestion was essentially 'dismissed' at the time, I'm not sure that I was necessarily wrong when, right at the start of this, I wrote:

Circumstantially speaking, is not the finger pointing at your UT-52B as the most likely 'culprit'?

Kind Regards, John

 

[JohnW2]

How would you know, the cockpit door are now locked and reinforced?

Well, if the 'cost saving' extended to not buying new uniforms for the re-purposed staff, I might get a bit suspicious if I saw the 'pilots' entering the flight deck wearing their cleaners' gear

Getting back to PAT'ing within BT and your raised point about recruiting from cleaning staff. As I mentioned we had to construct our own tester, after a short while our boss decided the testing within our 7 exchanges was too expensive for the engineering staff so he 'trained' one of the cleaners [lovely divorcee who I dated briefly] to use the machine, check fuse rating and rewire plugs ...

... say no more! Give or take the actual details, I could have predicted the rest of the story.

Of course, it is sometimes possible to properly train such 'untrained' people to undertake some circumscribed 'skilled' task(s), although that training still needs to include enough 'background' to enable them to know when they are out of their depth (and hence need 'more skilled' assistance) and/or to know how to deal with 'the unexpected' - but then, of course, one does not need 'idiot-proof' equipment.

It's had surprisingly little publicity, but one fairly 'dramatic' (and, to many people, surprising) example of this is that we have, for very many years, been using 'technicians' to undertake specific surgical procedures, or parts of surgical procedures, for which they have been specifically trained - but, again, they are using exactly the same 'tools' as do the fully-trained surgeons, not some 'dumbed down' versions!

Kind Regards, John

 

[ericmark]

It does not need to be cheapest PAT tester, we had quite an expensive one, but old, and first job was send it to be calabrated. And next was some nice new software to record results with, and had it not been for the software I would have likely not realised the problem.

PAT tester easy, green light pass red light fail it was 2000 so 20 years ago, but nothing wrong with that, but software wanted a figure entering, so phone call and answer was so simple could kick myself, enter the figure shown on calabration certificate, except it did not show the figure.

So got in touch to get the traceable record of the calabration in mean time returned software and used excel, easy to swap pass1 for what ever figure given, they could not find the traceable record and asked us to return PAT tester, then said it was so old the tester could not be calabrated to today's recommended limits, so every PAT test done invalid.

So when you look at the calibration certificate where a pass light or word comes up it should show at what point it actually shows, or if a meter of some sort, should show how far out the meter is, yes I know we don't trust calabration alone and use either another machine or some standard item to show if it drifts out, no good having a years testing being invalid as you don't know when the machine started to go wrong, one a week a rough test is done.