Poll

Which meter should be ran to celebrate 2000 subscribers?

Dave's new 121GW
58 (55.8%)
Gossen Metrawatt (you pick)
14 (13.5%)
HIOKI DT4282
6 (5.8%)
Anything but UNI-T (you pick)
1 (1%)
Anything made by UNI-T (you pick)
7 (6.7%)
I think the Fluke 87V is really a good meter and want to see if a third one would be better
10 (9.6%)
This testing is pointless! Please STOP damaging these meters!
8 (7.7%)

Total Members Voted: 103

Author Topic: Handheld meter electrical robustness testing.  (Read 395548 times)

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Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #2550 on: May 20, 2018, 10:33:58 am »
In order to repeat VoltLog's test the Joe Smith way, we can't use a handheld insulation tester as a source.   

Note, if your have a 1KV supply and your using your meter to measure the current from it and the 440mA fuse blows, the first thing you need to be aware of is you now have 1KV across your meter's current inputs.   And you guys wonder why I test this these things.     The second thing to note is working with 1KV at 440mA  could end your life.  A GFCI will trip in well under 10mA in 100ms or so.    Here we are playing with DC. 
How electrically robust is your meter?? http://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Online IanB

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Re: Handheld meter electrical robustness testing.
« Reply #2551 on: May 20, 2018, 11:59:29 am »
This is when you start to wish meters didn't use $10 fuses...
I'm not an EE--what am I doing here?
 

Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #2552 on: May 20, 2018, 04:00:05 pm »
The fuse cost more than the meter that caused it to blow.    Not sure how a half amp 240VAC glass fuse would like the 1KV DC.  Also not sure how many low end meters would survive with 1KV across their current inputs. 



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

Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #2553 on: May 27, 2018, 07:50:18 am »
Just a quick update on the T6.   I received this comment a while back:

Quote
The other problem with the non-contact voltage measurement of the T6, is that it is referencing to earth. When ever I am fault finding in a panel, I am testing phase to phase or phase to neutral as that is the working circuit. Testing phase to earth is poor measuring technique, and is predominantly done when testing of absence of voltage, which the T6 is unsuitable for.

It made no sense to me that the meter would not work using the non-contact mode when reference to something other than the earth ground.   So I tried it on a few 3P circuits using a one phase for a reference and the non-contact on the others and as expected, saw no problem at all using it this way.   Obviously you would have to have failed your studies if you were to touch the button and grab a live phase with your other hand.   I am using the black reference probe when doing these tests.

I also had access to another Mitsubishi VFD that I tried it on.   The VFD was running a motor.   No matter what I tried, I could not get the T6 to read the voltage.  This controller was running with a carrier at 5KHz.  The VFD was reprogrammed to 15KHz and the T6 worked fine.   We tried a few other lower frequencies and was unable to get the T6 to read. 

All of the testing I had done up till now with VFDs was at higher frequencies.  Leakage current may be a problem and I would assume many controllers will run low carriers.  My guess is the T6's non-contact feature will have problems with this. 

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

Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #2554 on: June 10, 2018, 06:27:53 am »
Effects of 1KV on PCB rotary switch.

How electrically robust is your meter?? http://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 
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Offline bitseeker

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Re: Handheld meter electrical robustness testing.
« Reply #2555 on: June 10, 2018, 07:08:36 am »
That was very effective, Joe. I hadn't thought about the case of the switch being rotated while overloaded. Dragging an arc is certainly plausible and pretty spectacular.
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Online IanB

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Re: Handheld meter electrical robustness testing.
« Reply #2556 on: June 10, 2018, 07:30:51 am »
Interesting. At 1000 V every mA is 1 W of power dissipation. It doesn't take many watts concentrated in a small area to cause heat damage. To make a multimeter completely idiot-proof and still work effectively at reasonable cost must be quite a challenge. One possibility might be some kind of mechanical interlock where you have to operate a separate off/disconnect switch before you can turn the dial. But then even the disconnect contacts would be subject to arcing...
I'm not an EE--what am I doing here?
 

Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #2557 on: June 10, 2018, 08:15:48 am »
Of course the 121GW is only rated to 600V. 

How electrically robust is your meter?? http://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 
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Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #2558 on: June 10, 2018, 08:26:17 am »
That was very effective, Joe. I hadn't thought about the case of the switch being rotated while overloaded. Dragging an arc is certainly plausible and pretty spectacular.

We have no way of knowing what happened with Kean's meter but I would not rule out high current / high voltage.   If I personally had damaged the 121GW like this, I would own it.  I may even try to replicate it for a video and then try to improve the design.

Interesting. At 1000 V every mA is 1 W of power dissipation. It doesn't take many watts concentrated in a small area to cause heat damage. To make a multimeter completely idiot-proof and still work effectively at reasonable cost must be quite a challenge. One possibility might be some kind of mechanical interlock where you have to operate a separate off/disconnect switch before you can turn the dial. But then even the disconnect contacts would be subject to arcing...

I'm not sure what could be done to prevent something like this.  Normally at home if I am working with KV and higher the currents are sub mA.   I have been testing all the meters with the full rectified 220V AC and limit the current to something around 40mA.   I've had a few meters get damaged during this test.   At a KV it's going to be even more difficult to try and save the PCB.  Something to think about.
How electrically robust is your meter?? http://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Online IanB

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Re: Handheld meter electrical robustness testing.
« Reply #2559 on: June 10, 2018, 11:23:16 am »
At least the cheap Harbor Freight meters have appropriate warnings in the instructions.  They clearly say you should wear gloves, eye protection and full PPE before using the meter...
I'm not an EE--what am I doing here?
 

Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #2560 on: June 11, 2018, 12:45:28 am »
The spreadsheet now contains the test results for the latest revision of the Fluke 87V along with the repaired revision 10 unit. 
How electrically robust is your meter?? http://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #2561 on: June 11, 2018, 10:36:41 am »
After watching Dave's latest videos where he exposes the 121GW to 1100V DC to show that the contacts would not arc over at those levels, I decided to repeat the same test with the free DT830 meter from Harbor Freight.   The new ones are only rated to 250VDC.  Will it survive with 4 X it's rated voltage??  Seems like a tall order for a free meter....

No attenuators were used in the making of this video

How electrically robust is your meter?? http://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 
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Offline bitseeker

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Re: Handheld meter electrical robustness testing.
« Reply #2562 on: June 11, 2018, 02:20:39 pm »
Hmm, I wonder if something happened with one or more of the free DMMs that triggered the relabeling of the uppermost ranges.
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Offline Fungus

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Re: Handheld meter electrical robustness testing.
« Reply #2563 on: June 11, 2018, 04:52:52 pm »
The new ones are only rated to 250VDC.

Interesting.

The $20 Zotech/ANENG style meters have just dropped down a whole CAT level, now these are only rated labelled to 250V. I wonder if somebody's getting tough on them.
« Last Edit: June 11, 2018, 05:22:59 pm by Fungus »
 

Offline bitseeker

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Re: Handheld meter electrical robustness testing.
« Reply #2564 on: June 11, 2018, 05:04:00 pm »
Sounds like it. 'Bout time. ^-^
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Offline stj

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Re: Handheld meter electrical robustness testing.
« Reply #2565 on: June 11, 2018, 07:49:45 pm »
one poss fix to arc-over is if the switch is covered in some type of insulating slime or grease that has a consistancy like gell.
i have seen something like this in some old industrial switches for starting large engines - before they started using relays.
 

Offline Kean

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Re: Handheld meter electrical robustness testing.
« Reply #2566 on: June 11, 2018, 11:06:00 pm »
We have no way of knowing what happened with Kean's meter but I would not rule out high current / high voltage.   If I personally had damaged the 121GW like this, I would own it.  I may even try to replicate it for a video and then try to improve the design.
Yeah, I'm happy to "own it".  :-DD

As I've mentioned in the YT comments and 121GW forum post, it looks like I screwed up and used the 121GW when I shouldn't have - measuring the HV output of an ultrasonic transducer driver.  Roughly 1200V at 25-28kHz, at potentially 100W!

I don't remember doing this, but it really seems like I must have.   :palm:  And I very likely didn't use this meter again till I went to measure that flakey DC/DC converter a week or so later and saw 166V, then OFL, instead of 5V.  It measured more like 3.5V on an EEVblog/Brymen 235 meter, and that was fixed with some extra input capacitance.

I tried to reproduce the damaging arc on a test PCB - an SMD breakout with approx the same 1mm trace gap.  I was set up to take video and everything, but it just wouldn't arc over by itself, and I wasn't game to manually start the arc like Joe did.  Most likely would have killed my driver board.

And I'm also happy to say that the meter survived after cleanup of the PCB.  Even the protection diodes that are in the path seem to measure fine (forward voltage and leakage).   :-+

Thanks again Joe for the excellent series of testing videos you've been producing.   :-+ :-+
 
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Offline rsjsouza

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Re: Handheld meter electrical robustness testing.
« Reply #2567 on: June 12, 2018, 03:51:40 am »
Joe, thanks for the HF testing; I have done this myself several years ago without issues, but I had them thoroughly disassembled and scrubbed for subpar production quality - i.e., loose springs, screws or solder blobs.

My oldest M830B meter is quite well built and this thread shows many internal photographs of "830" models over the years, including the latest derating on the maximum voltage specs.
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Offline bitseeker

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Re: Handheld meter electrical robustness testing.
« Reply #2568 on: June 12, 2018, 05:28:58 am »
Thanks for the update, Kean. Mystery solved.
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Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #2569 on: July 03, 2018, 10:07:09 pm »
CAT ratings while working in the home.

It was late and while we were watching a movie, a storm kicked up.   Part way through the movie we heard a big boom.  It's near the 4th so there are a lot of fireworks but this was much louder and the outside was a large flash.  I made my wife stay inside while I checked to see if the house had been hit.   No signs of a fire.   We both went outside to investigate and the neighbors were out as well to check.   It seems a bolt hit a tree in our yard and traveled to the roots.  The roots appear to have made contact with the phone can coax cable.   It blew the cover off the phone box but there was no signs of damage.     The phone cable is not in use.    The coax feds the modem only.   The modem was dead.  The modem contains a GDT which had signs of a major strike.  The area around the transformer (data) had blown a few components blown off the PCB.     The VOIP box that was connected to the Ethernet was also damaged.  Both wall power supplies for these devices are still fine.  These were running off a UPS.   

It also made it's way into the AC mains and we lost a few devices.  People have talked about the CAT ratings in a home and how the energy is limited.     The part about this I like is that we are no longer limited by fuses on a pole or some upstream transformer and cable losses.    All those CAT ratings go out the window. 

The garage door opener has two half inch sparkgaps made into the PCB with an isolation slit.  The arc jumped this and vaporized several traces.  There's a TVS downstream, that was gone.   

One of the lightbulbs that was lost looks to have a fair amount of damage to the base.  It's a CFL.  Perhaps they are more mechanically robust than an incandescent bulb.

I've looked at a lot of meters that I wouldn't want to be using that day in a CAT II environment....     

Furthest sod was about 20' from the base of the tree.    For those that have written me suggesting that my little transients are too harsh and how things like this can't happen,  I stand by what I have said all along.  My little transients are nothing.   
How electrically robust is your meter?? http://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 
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Offline saturation

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Re: Handheld meter electrical robustness testing.
« Reply #2570 on: July 04, 2018, 12:29:49 am »
Joe do you have any surge protectors plugged into these circuits at the time of the strike?  Even if working some of them could be toast inside, if so photos please.  Folks capable of making informed engineer level reports about strikes are not common so your opinion and photos would be a plus.

CAT ratings while working in the home...
Best Wishes,

 Saturation
 

Offline rsjsouza

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Re: Handheld meter electrical robustness testing.
« Reply #2571 on: July 04, 2018, 12:50:59 am »
Joe, sorry for the losses around your house. Fortunately no one was hurt apart from the tree. I suspect you will have your hands full reporting the damages with lots of photographs and short videos and reworking a few of the least damaged ones - if not for your channel perhaps to the insurance company (is that applicable?). 

I would keep a close track on how the tree goes from now on; it may have caused some severe damage to its internal systems and it may be partially or totally dead.

Taking into consideration the damage done, it is a coin toss on how any CAT rated meter would help the operator survive; however, the chances would be obviously much higher with a truly certified one.

In a distant past (in the ages where 14.4kbps POTS modems were the new thing), the apartment building right beside us was hit by lightning, which ruined many of the appliances and electronics of that building. I was working on the computer at the time and it simply rebooted with the transient - fortunately I was not connected to the BBS and we used to leave the modem disconnected via an ancient dual pole 20A disconnect switch similar to this one.


Despite our pride in our disconnect switch, at about the same time a friend of mine experienced a discharge that went through his house (metal piping) and destroyed the regular appliances/electronics and even destroyed some of the masonry walls (houses in Brasil are brick-and-mortar). This gave me the realization that no matter what we use to protect the appliances, when a lightning strikes we should forget them and need to be thankful that we are simply alive.  :-BROKE

 
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Oh, the "whys" of the datasheets... The information is there not to be an axiomatic truth, but instead each speck of data must be slowly inhaled while carefully performing a deep search inside oneself to find the true metaphysical sense...
 

Offline BillB

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Re: Handheld meter electrical robustness testing.
« Reply #2572 on: July 04, 2018, 01:55:00 am »
Joe do you have any surge protectors plugged into these circuits at the time of the strike?  Even if working some of them could be toast inside, if so photos please.  Folks capable of making informed engineer level reports about strikes are not common so your opinion and photos would be a plus.

+1

Sorry about the damage, and glad nobody was hurt.  Pictures of lightning destroyed stuff are always welcomed!
 

Offline bitseeker

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Re: Handheld meter electrical robustness testing.
« Reply #2573 on: July 04, 2018, 06:19:27 am »
Wow, Joe. That's quite the fallout from a strike. I haven't experienced a direct hit like that. It certainly is a wakeup call. Out of habit, I generally turn off power strips when leaving for an extended period, but with a lightning strike, I suppose that doesn't really help. It sounds like the surge would jump right past the switch.
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Offline stj

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Re: Handheld meter electrical robustness testing.
« Reply #2574 on: July 04, 2018, 06:21:32 am »
check everything you have with an ethernet port to see if they still work.
unfortunatly i have seen a lot of dead network interface chips caused by lightning - the emp gets into the transformer and kills the controller even if the port is not connected.
 


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