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 523306 times)

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Offline bitseeker

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Re: Handheld meter electrical robustness testing.
« Reply #2550 on: June 09, 2018, 09:08:36 pm »
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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Offline IanB

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Re: Handheld meter electrical robustness testing.
« Reply #2551 on: June 09, 2018, 09:30:51 pm »
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...
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Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #2552 on: June 09, 2018, 10:15:48 pm »
Of course the 121GW is only rated to 600V. 

https://youtu.be/3oGEKVp0bso
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 
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Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #2553 on: June 09, 2018, 10:26:17 pm »
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?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline IanB

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Re: Handheld meter electrical robustness testing.
« Reply #2554 on: June 10, 2018, 01:23:16 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...
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Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #2555 on: June 10, 2018, 02:45:28 pm »
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?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #2556 on: June 11, 2018, 12:36:41 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

https://youtu.be/mjTzMR-7ilo
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 
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Offline bitseeker

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Re: Handheld meter electrical robustness testing.
« Reply #2557 on: June 11, 2018, 04:20:39 am »
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 #2558 on: June 11, 2018, 06:52:52 am »
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, 07:22:59 am by Fungus »
 

Offline bitseeker

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Re: Handheld meter electrical robustness testing.
« Reply #2559 on: June 11, 2018, 07:04:00 am »
Sounds like it. 'Bout time. ^-^
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Offline stj

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Re: Handheld meter electrical robustness testing.
« Reply #2560 on: June 11, 2018, 09:49:45 am »
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 #2561 on: June 11, 2018, 01:06:00 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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Online rsjsouza

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Re: Handheld meter electrical robustness testing.
« Reply #2562 on: June 11, 2018, 05:51:40 pm »
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.
Vbe - vídeo blog eletrônico http://videos.vbeletronico.com

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Offline bitseeker

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Re: Handheld meter electrical robustness testing.
« Reply #2563 on: June 11, 2018, 07:28:58 pm »
Thanks for the update, Kean. Mystery solved.
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Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #2564 on: July 03, 2018, 12:07:09 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?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 
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Offline saturation

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Re: Handheld meter electrical robustness testing.
« Reply #2565 on: July 03, 2018, 02:29:49 pm »
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
 

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Re: Handheld meter electrical robustness testing.
« Reply #2566 on: July 03, 2018, 02:50:59 pm »
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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Offline BillB

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Re: Handheld meter electrical robustness testing.
« Reply #2567 on: July 03, 2018, 03:55:00 pm »
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 #2568 on: July 03, 2018, 08:19:27 pm »
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 #2569 on: July 03, 2018, 08:21:32 pm »
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.
 

Offline bitseeker

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Re: Handheld meter electrical robustness testing.
« Reply #2570 on: July 03, 2018, 08:25:28 pm »
Woah :o
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Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #2571 on: July 03, 2018, 11:02:14 pm »
Well, it's starting to look bad.  I had my old HP spectrum analyzer apart for service and went to set it back up only to discover that I have some major problems with the test equipment.   Most of this is very old and for insurance, it's a bit of a question what to even do about it.  As it stands, I can't even access the level of damage because the equipment I need to use is dead. 

Everything was off at the equipment as well as the bus strips were all off.   

On the Ethernet side of things, the modem goes to the VOIP.  The only other thing I normally would have tied into it is a laptop.  With Windows 10 phoning home non-stop and disrupting anything I do with the laptop,  I had it unplugged and it survived! That's right, Windows 10's performance is so bad it saved that hardware.   :-DD :-DD 

The modem talks wireless to another router that I have all my Windows 10 blocking on.  This then runs all of the test equipment and PCs.   

I recently posted about changing one of my UPSs to use super caps rather than lead acid.   This UPS has a fair bit of protection.  I had just put it on-line a few days prior.  It was running at the time of the strike and continues to run.  It appears to have no signs of any damage.  There is no damage to anything that was running from it.   

The test equipment is my biggest concern at the moment.   Several years to accumulate and repair.  At least my old HP 3589A is in perfect working order again so take that mother nature!  :box:
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 
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Offline IanB

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Re: Handheld meter electrical robustness testing.
« Reply #2572 on: July 03, 2018, 11:19:46 pm »
Well, it's starting to look bad.  I had my old HP spectrum analyzer apart for service and went to set it back up only to discover that I have some major problems with the test equipment.   Most of this is very old and for insurance, it's a bit of a question what to even do about it.  As it stands, I can't even access the level of damage because the equipment I need to use is dead.

Well, shit, that's bad  :(
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Offline 2N3055

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Re: Handheld meter electrical robustness testing.
« Reply #2573 on: July 03, 2018, 11:30:01 pm »
Sorry to hear that Joe...

With a hit that close, at least some damage will come from induced (EMP style) pulse, in addition to any conducted overvoltage...

Hope there is not much more damage, and good that nobody got hurt.

Regards,

Sinisa
 
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Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #2574 on: July 03, 2018, 11:38:08 pm »
Well, it's starting to look bad.  I had my old HP spectrum analyzer apart for service and went to set it back up only to discover that I have some major problems with the test equipment.   Most of this is very old and for insurance, it's a bit of a question what to even do about it.  As it stands, I can't even access the level of damage because the equipment I need to use is dead.

Well, shit, that's bad  :(

It's not that bad.  The house was not damaged and no one was injured.   And the HP3589A was being serviced at the time and in parts.  No where near an outlet. Also on the plus side, my trusty PACE soldering iron survived. 

Looking at my two Ethernet GPIB controllers, they were built roughly the same time.  One has a heat shrink around what appears to be a couple of large MOVs.  The other does not.  One has a plastic sheet isolating the power supply from the digital section, the other does not.   Both were turned off, both no longer pass the basic diagnostics.  Expecting to see some chips blown apart, there really is nothing exciting.  Nothing even running all that hot.  Custom ASICs, so not going to be able to do anything with them.   Time to drag out an old GPIB controller...
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 


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