Poll

Are you interested in seeing more handheld meters tested?

This testing is pointless! Please STOP damaging these meters!
3 (6.4%)
 Yes, I would like to more meters tested.
44 (93.6%)

Total Members Voted: 47

Author Topic: Handheld meter electrical robustness testing.  (Read 509406 times)

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Offline true

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Re: Handheld meter electrical robustness testing.
« Reply #2800 on: September 01, 2018, 02:59:50 pm »
Are you doing harsh work with these meters or is this some unknown weakness they have?
If I was I would have mentioned it. As I said, my replacement was used twice to measure a simple 5VDC circuit. Between the first and second time - as in, before it was used the second time, it failed. The other meters are also not abused in any way, usually used for low voltage DC circuits and simple tests.

You could try go up to 3.3V for power to see if it's a battery issue. But the defunct ranges seem to point out the mux, as a guess.

I checked and the Brymen 27s has legit 61010 UL certification, so it should not be fragile for ESD.
Unless the plastic shield inadvertently allows arcs between internal nodes on the PCB...
I'm not thinking it's ESD though it could be possible. I noticed this when my meter crapped out after it had a low battery. I ordered a replacement, and my friend said the same thing. I checked my old PM55 which worked last time, and sure enough, same thing. My replacement PM55A showed good voltage on battery, but next time I went to use it, low battery...checked ohms range, sure enough, same fault. Replaced battery with fresh, tested cell, fault still exists.

Not to blame the low battery, but that, and non-harsh use, are the only similarities. But perhaps the zip-up case they come in can generate enough ESD to blow something up?
 

Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #2801 on: September 02, 2018, 01:31:14 am »
A bit late, but I can say, every Meterman PM55 or Amprobe PM55A I have has failed.

What happens:
- Auto mode freaks out and doesn't work (a short shows an unstable high resistance for example)
- Short detect mode shows shorted
- EF (power stick) mode works
- I can't remember what Low-Z volts does
- Hi-Z voltage works
- Diode mode acts like a short
- High ohms varies from not working to usually sounding the "shorted" beeper; IIRC high ohms will not give a stable reading
- Haven't tested current

What causes this?

The only similar thing I could find was a dying battery.

I purchased a new unit after my PM55A had failed, only to find a PM55 I gave to a friend also failed. I tested a PM55 I had and it too had failed. The replacement? Well, it tested good (testing 5V in auto mode, and shorting probes, that's it...); after a month when I went to use it to test a low voltage DC circuit again, it showed low battery ... and sure enough it failed too.

I'd like to fix them but have no idea where to start or what could have failed.
I read through your posts.  First, I am not understanding why you would have posted in this thread of all places vs starting a new one.  There is even a repair section that had you used, may have brought more attention/help.   Is there some reason you keep buying the same meter with the same problem?  There is a word for that.  Then again, I have bought more than one of the same meter just to damage them so, welcome to the the club. 

Have you tried to contact Brymen directly about what you are seeing?  If so, what was their response?   What about contacting AMPROBE or the distributor you procured them from? 

I have never looked at this specific meter and really can't offer any suggestions on what may have failed and why. 
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline MiroS

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Re: Handheld meter electrical robustness testing.
« Reply #2802 on: September 04, 2018, 11:39:20 pm »
> Is there some reason you keep buying the same meter with the same problem?

I think Joe is doing a great work we are or will apprciate.  See 87V two tests - two results ...
For sceptics - see autopsy of FK87V. Joe tests are very delicate I would say.


 

Offline true

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Re: Handheld meter electrical robustness testing.
« Reply #2803 on: September 05, 2018, 03:28:36 am »
I read through your posts.  First, I am not understanding why you would have posted in this thread of all places vs starting a new one. There is even a repair section that had you used, may have brought more attention/help.
Maybe I should? I don't have much time to go over repair on this right now, but plan to post when I do have time, and wanted to make mention where it may be noticed. If this thing fails so easily it may be worth testing, especially if it ends up the failure was ESD induced. Maybe someone is willing to do some tests if they have one that hasn't yet died - that's why I posted here for now. Still maybe not relevant enough, I don't know.

Is there some reason you keep buying the same meter with the same problem?
Because I was not aware of the problem when I ordered my replacement.

I purchased my replacement because my unit was dead and I could not find anyone with similar problems. The order was done before I learned that the Meterman-branded unit I gave my friend failed - because, well, he doesn't share all his life details with me. I made mention I ordered a replacement and then he told me his failed. I went and checked my other meter at the house and sure enough, it had failed.

There is a word for that.
Right.

Then again, I have bought more than one of the same meter just to damage them so, welcome to the the club.
I bought these to use them. Before they failed, I quite liked them.

Have you tried to contact Brymen directly about what you are seeing?  If so, what was their response?   What about contacting AMPROBE or the distributor you procured them from?
Until this latest one, all were out of warranty - Meterman has long since been bought out and Amprobe only has short warranties. I've reached out to Amprobe with no response so I will try again. Ultimately they won't be interested in telling me what the fault is anyway, thus posting here.  But not in a good enough way / its own thread I guess. And if they repair it, I don't know that it won't fail again.
 

Online IanB

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Re: Handheld meter electrical robustness testing.
« Reply #2804 on: September 05, 2018, 03:47:36 am »
A bit late, but I can say, every Meterman PM55 or Amprobe PM55A I have has failed.

What happens:
- Auto mode freaks out and doesn't work (a short shows an unstable high resistance for example)
- Short detect mode shows shorted
- EF (power stick) mode works
- I can't remember what Low-Z volts does
- Hi-Z voltage works
- Diode mode acts like a short
- High ohms varies from not working to usually sounding the "shorted" beeper; IIRC high ohms will not give a stable reading
- Haven't tested current

What causes this?

The only similar thing I could find was a dying battery.

I purchased a new unit after my PM55A had failed, only to find a PM55 I gave to a friend also failed. I tested a PM55 I had and it too had failed. The replacement? Well, it tested good (testing 5V in auto mode, and shorting probes, that's it...); after a month when I went to use it to test a low voltage DC circuit again, it showed low battery ... and sure enough it failed too.

I'd like to fix them but have no idea where to start or what could have failed.

I agree with Joe that starting a new thread with a title containing the keywords "Meterman Amprobe PM55 Problems" would probably have gained more attention than tagging on the end of this thread.

However, the symptoms you list above make me wonder if something is wrong with the rotary selection switch. Something could have gone wrong with the contacts. This may happen with low cost meters due to oxidation causing poor contact or mechanical wear producing metal dust and debris causing shorts.

A good start to investigation might be to disassemble the meter and closely examine the range selector mechanism.
I'm not an EE--what am I doing here?
 

Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #2805 on: September 05, 2018, 03:51:03 am »
Based on your initial post, I assumed your goal was to repair them.  I would ask in the repair section.  If your goal was to attempt to have me run one, it's an odd way to go about it.  Most people would simply ask. 

If it is a Brymen product as suggested, they would be the first company I would contact.   The only reason I would reach out to AMPROBE or the distributor would be to try and have them covered. 

It looks like you have had them for 5 years or so.  I certainly would have no way of knowing how they were treated during this time.   It appears they are still available so it would be possible to see how they fair against the other meters I have looked at. 
 
https://www.eevblog.com/forum/testgear/review-uni-t-ut136b-tired-of-the-multimeter-snobs-a-very-nice-budget-meter!/msg242028/#msg242028

How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #2806 on: September 05, 2018, 03:54:28 am »
> Is there some reason you keep buying the same meter with the same problem?

I think Joe is doing a great work we are or will apprciate.  See 87V two tests - two results ...
For sceptics - see autopsy of FK87V. Joe tests are very delicate I would say.

ROFLMAO!  Very nice!  Is there a story that goes with these pictures? 
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline MiroS

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Re: Handheld meter electrical robustness testing.
« Reply #2807 on: September 06, 2018, 07:26:57 pm »
ROFLMAO!  Very nice!  Is there a story that goes with these pictures?
[/quote]

Unfortunately not mine, no idea how this has happened.  Anyway prvoked my head to some questions:
- Majority of damage is caused by this fused resistor, it fired PCB, internal plastic protection  and even the case. Hmm... this looks like this resistor was too slow to cut connection and made huge explosion and fire.  Shuould  fused resisitor really explode? Is plastic protection a correct protection from fire?
- PTC was compeltely melted and changed to cloud of smoke. Maybe it shuld be heatshrinked to react faster on overrload (heat cumuates faster when PTC is shrinked?)
- MOVs exploded, but PCB trace to MOVs surrived intact, hmmm ... why?
- None of fuses exploded or broke connection, hmm ...all were just fine. No they were not repalced after damage, all were nicely smoked.



 

Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #2808 on: September 06, 2018, 08:56:27 pm »
Unfortunately not mine, no idea how this has happened.  Anyway prvoked my head to some questions:
That's too bad.  Knowing about the fuses,  suggests you may have met the owner.   

Quote
- Majority of damage is caused by this fused resistor, it fired PCB, internal plastic protection  and even the case. Hmm... this looks like this resistor was too slow to cut connection and made huge explosion and fire.  Shuould  fused resisitor really explode? Is plastic protection a correct protection from fire?

Even with my small transients and the camera running at close to 1ms frame rates, it's no where fast enough to capture an event like this.  I see a lot of people post about the input protection circuit is for safety.  As you can see from the picture, the case plays a big part.   

If you exceed the design limits of any component, I am guessing you could see it fail in the same manor.   PhotonicInduction made a few videos where he placed some HRC fuses across a large high voltage capacitor and was able to get them to rupture.   These were 10KA+ break currents.  So even a safety fuse will have it's limits.  :-DD   That was a very interesting channel to watch.  Nothing I would ever attempt at home. 

Quote
- PTC was compeltely melted and changed to cloud of smoke. Maybe it shuld be heatshrinked to react faster on overrload (heat cumuates faster when PTC is shrinked?)

I doubt heat shrunk tube would do much in this case.   I've seen it used a fair amount on the smaller PTCs but not the larger ones.   During my tests, I've damaged a fair number of PTCs in low end meters.  They often use 5mm parts which don't always hold up very well.   

Quote
- MOVs exploded, but PCB trace to MOVs surrived intact, hmmm ... why?
Higher resistance, more power dissipated?   

Quote
- None of fuses exploded or broke connection, hmm ...all were just fine. No they were not repalced after damage, all were nicely smoked.
Why would the fuses be effected.  It's obvious that what ever happened, it was on the voltage circuit of the meter, not the current. 

I would say in this case, trying to make a meter survive what ever happened is not solving the root problem.  With so little damage done to the meter, I doubt the person was harmed and may not have learned anything from it.   Next time, they may not be so lucky.     
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline malagas_on_fire

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Re: Handheld meter electrical robustness testing.
« Reply #2809 on: September 06, 2018, 09:48:28 pm »
Wow that is  a toasted meter .

Did some put DC voltage , MOT on that meter? Maybe a higher spike.  this looks like a result of the half cycle simulator but with even more energy.

If one can make knowledge flow than it will go from negative to positve , for real
 

Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #2810 on: September 06, 2018, 10:01:26 pm »
Wow that is  a toasted meter .

Did some put DC voltage , MOT on that meter? Maybe a higher spike.  this looks like a result of the half cycle simulator but with even more energy.

There's not enough damage to where I would have guessed it was on a HV mains bus.  I could not do anywhere near this damage to a Fluke with the half cycle generator.  I've shown it attached to a few of the better meters.  Nothing happens.  The voltage is too low.  I'm going with a kid and their MOT.  :-DD 
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline malagas_on_fire

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Re: Handheld meter electrical robustness testing.
« Reply #2811 on: September 07, 2018, 10:08:37 am »
well the worst meters got in bad shape with the half cycle simulator and then not a lot of energy to  upset fluke, brymen.

So if a Fluke got to that point that's should be called the how to not use a Fluke ... for repair Microwave  HV sources ... aka MOT... or maybe a CRT tv or monitor...

If one can make knowledge flow than it will go from negative to positve , for real
 

Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #2812 on: September 07, 2018, 10:54:58 am »
A meter would need to break (have a low impedance path) for the half cycle simulator to do anything.   The Fluke's normally don't break down so the energy just dissipates inside the generators.  There always the same amount of energy available, but if a meter is an open circuit it won't present much of a load.   

The CRT is a good one.  I liked this guys video.  When I asked about what the cause was they explained that it was a HV supply for the display.  You can't blame Fluke, or any other meter for not holding up to this abuse.   

How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline stj

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Re: Handheld meter electrical robustness testing.
« Reply #2813 on: September 07, 2018, 08:06:51 pm »
i have seen a similar chared mess in a cheaper meter once.
some idiot thought it would be a good idea to diagnose an engine problem by metering the voltage at the spark plugs!  :palm:

i laughed my ass off when he told me how he killed his meter.  :-DD
 

Offline malagas_on_fire

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Re: Handheld meter electrical robustness testing.
« Reply #2814 on: September 07, 2018, 09:28:42 pm »
Yeah the fluke's are made to deal with that kind of stress, but man an engineer plug the meter to the CRT tube???? Thank that it was in a good technician able to repair the 189.

What a waste of bad usage on such a good meter. It is very easy to kill cheap meters with a flyswatter or a insulator tester with 5kV capability as they are available for selling.... Now damage a fluke in that manner is lack of responsability , knowledge of specs.
If one can make knowledge flow than it will go from negative to positve , for real
 
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Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #2815 on: September 08, 2018, 10:14:00 am »
i have seen a similar chared mess in a cheaper meter once.
some idiot thought it would be a good idea to diagnose an engine problem by metering the voltage at the spark plugs!  :palm:

i laughed my ass off when he told me how he killed his meter.  :-DD

I would never have guessed a car ignition system would burn a board like this.   I tried a few early meters across my MSD with little effect.
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline stj

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Re: Handheld meter electrical robustness testing.
« Reply #2816 on: September 08, 2018, 07:11:56 pm »
constant stream of high current sparks from an oil-cooled transformer can do a lot of damage.
 

Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #2817 on: September 09, 2018, 12:22:58 pm »
constant stream of high current sparks from an oil-cooled transformer can do a lot of damage.
Agree that any transformer that can put out high voltage and high current could do a lot of damage but my ignition coils don't put out a lot of current.  I could try to burn a meter down with one. 

****

I did show a neon sign transformer hooked up to a few early on.  That's a bit more current than I can get out of any of my ignition coils.   
« Last Edit: September 09, 2018, 12:24:31 pm by joeqsmith »
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline stj

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Re: Handheld meter electrical robustness testing.
« Reply #2818 on: September 09, 2018, 12:30:14 pm »
how are you driving the coil?
modern cars use capacitive discharge to give the coil a good kick.
 

Online tautech

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Re: Handheld meter electrical robustness testing.
« Reply #2819 on: September 09, 2018, 12:37:40 pm »
how are you driving the coil?
modern cars use capacitive discharge to give the coil a good kick.
MSD racing ignition systems provide far more power than anything from 'consumer' automotive manufacturers.
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Online IanB

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Re: Handheld meter electrical robustness testing.
« Reply #2820 on: September 09, 2018, 12:44:55 pm »
Agree that any transformer that can put out high voltage and high current could do a lot of damage but my ignition coils don't put out a lot of current.  I could try to burn a meter down with one. 

Clearly we need to see a meter hooked up to the ~10 kV circuit on the high side of a mains distribution transformer. Though it would have to be a disposable meter as I think it would be completely vaporized in a fireball of epic proportions...
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Offline SeanB

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Re: Handheld meter electrical robustness testing.
« Reply #2821 on: September 09, 2018, 06:15:31 pm »
Agree that any transformer that can put out high voltage and high current could do a lot of damage but my ignition coils don't put out a lot of current.  I could try to burn a meter down with one. 

Clearly we need to see a meter hooked up to the ~10 kV circuit on the high side of a mains distribution transformer. Though it would have to be a disposable meter as I think it would be completely vaporized in a fireball of epic proportions...

Fluke 77 does survive that with the case intact, though the leads do become a lot shorter. Inside the case however there is a nice copper plate on the plastic inside, and the lower half under the display of the board is remarkably free from any traces, aside from where the components are soldered to the board. The fuses do not blow.
 

Offline stj

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Re: Handheld meter electrical robustness testing.
« Reply #2822 on: September 09, 2018, 09:35:48 pm »
how are you driving the coil?
modern cars use capacitive discharge to give the coil a good kick.
MSD racing ignition systems provide far more power than anything from 'consumer' automotive manufacturers.
"systems", yes.
not just the coil - it's all about the drive circuit.
 

Online tautech

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Re: Handheld meter electrical robustness testing.
« Reply #2823 on: September 09, 2018, 09:46:12 pm »
how are you driving the coil?
modern cars use capacitive discharge to give the coil a good kick.
MSD racing ignition systems provide far more power than anything from 'consumer' automotive manufacturers.
"systems", yes.
not just the coil - it's all about the drive circuit.
Joe knows and so do I. The last MSD CD drive unit I scoped was ~400V but as it was a bit older so nowhere near the Joules they make these days. Something like Methanol of top fuel with a bucket load of boost up its arse is pretty hard to light.
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Offline malagas_on_fire

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Re: Handheld meter electrical robustness testing.
« Reply #2824 on: September 10, 2018, 02:17:15 am »
Definitly from the video its quite  a big spark and supposelly the meter is automotive... very susceptible to the spark till reset point.  Imagine doing the same on the cheaper ones...
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