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 515897 times)

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Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #2950 on: October 29, 2018, 10:27:57 pm »
I could try installing one and see if there are any long term effects.  If it damages the meter, it doesn't mean that's what happened with all four of True's meters.   It also doesn't mean there is anything wrong with the design.  I wouldn't expect to be able to use a different battery than the manufacture calls for without damage.   
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 #2951 on: October 30, 2018, 12:33:22 am »
Well there always the chance of flipping the polarity , but four in a row would be a bad play.  :-DD
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 #2952 on: October 30, 2018, 12:42:33 am »
Seems like Voltlog mentioned that it had reverse protection.  I think they shunt it with a diode.  Still I know I didn't test it.  It would be pretty bad though as the meter is marked in at least two places, plus the manual.  Still....  :-DD
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 #2953 on: October 30, 2018, 11:19:46 am »
About my meter looks like one of my brothers use it to measure the voltage of the flyswatter and it said it was doing OL all the time and switched to other off position while the thing still on and leads plugged  :palm: . i. , before i ran the 230V ac test... I thought it was the fall but now i have the oportunity to offer one of my old meters, the uni-t 50b, teach more stuff. All bets are off for now.... :-DD

on the left side of the battery holder is a supressor diode - see if it's shorted or try the meter without it.
i got an aneng from someone who did something stupid, and that was blown.
 

Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #2954 on: October 30, 2018, 05:00:23 pm »
From what I remember, that TVS was for the current input and I thought it was on the backside of the switch.   :-//  I may have scribbled out that circuit when I made the video where I had modified the meter.
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 #2955 on: October 30, 2018, 08:26:58 pm »
Are you refering to the Q3 that was blown or the TVS on the current input? I can probe later the Q3 if it is shorted and maybe take it out.



Well i have probe Q3 and Q4 are shorted.... maybe i'll take out later and fingers crossed
« Last Edit: October 30, 2018, 08:33:26 pm by malagas_on_fire »
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Offline stj

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Re: Handheld meter electrical robustness testing.
« Reply #2956 on: October 30, 2018, 08:51:59 pm »
i was refering to the tvs,
people who dont read instructions dont know the current mode is limited to about 50v
 

Offline malagas_on_fire

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Re: Handheld meter electrical robustness testing.
« Reply #2957 on: October 30, 2018, 09:58:06 pm »
Yes in most cheap meters its more or less 30 Vrms on the current side. I've removed the Q3 / Q4 and the TVS., plug the batteries, no meter.

The TVS shows no voltage in diode mode in both directions,  aka O.L. meanwhile i've ordered a replacement meter... one of the most cheapest true RMS meters for measuring voltages up to 600V, but i'm using max 230V. Bet you're guesses and it is similar to one that joe smith has tested :P
If one can make knowledge flow than it will go from negative to positve , for real
 

Offline HKJ

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Re: Handheld meter electrical robustness testing.
« Reply #2958 on: October 30, 2018, 10:05:52 pm »
Yes in most cheap meters its more or less 30 Vrms on the current side. I've removed the Q3 / Q4 and the TVS., plug the batteries, no meter.

There is no voltage limit when measuring current, even on cheap meters. The TVS diode is there to protect the current shunt during over current conditions until the fuse blows.
If the fuse blows it may not be able to break the current and higher voltage may damage the meter.
 

Offline malagas_on_fire

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Re: Handheld meter electrical robustness testing.
« Reply #2959 on: October 30, 2018, 10:27:00 pm »
At least on the manual on the uni-t 50b it calls for 30Vrms maximum.input .. but this is a meter with unfused A and fused mA , so it gets even worse...
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Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #2960 on: October 30, 2018, 11:58:36 pm »
Demonstrating my software for the UEI / EEVBLOG 121GW and the UNI-T UT-181A.    This video also contains a test that 001 and Fungus had requested using high voltages, a spark gap and Vaseline.   :palm:   For future reference, that thread may be found here:

https://www.eevblog.com/forum/testgear/can-i-grease-my-dmm-selector-with-silicone-oil/

https://youtu.be/e_YzwO62feQ
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 
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Offline malagas_on_fire

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Re: Handheld meter electrical robustness testing.
« Reply #2961 on: October 31, 2018, 12:50:39 am »
Now it is using my old uni-t 50b and read the manual before using it. They are the acessible meters.
The one that i've got is the uni-t ut139A , the worst of the 139 line. At least it has ceramic fuses for the claimed voltage, it has enough grip and simple to use. It will be out of reach for modifications.
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Online Fungus

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Re: Handheld meter electrical robustness testing.
« Reply #2962 on: October 31, 2018, 08:47:01 am »
Just to be clear: I didn't request Vaseline, that was 001.  I just suggested the spark gap test.  :D

 
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Offline malagas_on_fire

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Re: Handheld meter electrical robustness testing.
« Reply #2963 on: October 31, 2018, 09:37:26 am »
I only watch the video till the labview interface because it was too late and damn, very nice. Very Good algorithm for using the A/D. looks like the BLE interface may fit the uni-t 81b scope. I've contacted uni-t but no answer yet.

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 #2964 on: October 31, 2018, 11:08:43 am »
Just to be clear: I didn't request Vaseline, that was 001.  I just suggested the spark gap test.  :D

If that's a concern for you, next time perhaps think more, post less? 

Simple test: Make a spark gap, put Vaseline on it, see if it stops sparking.  :popcorn:

(and if it stops, how much higher do you need to go to get it to spark again?)

I provided a link to the thread in the description for those wanting to read what's been posted and follow along.
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 
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Online Fungus

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Re: Handheld meter electrical robustness testing.
« Reply #2965 on: October 31, 2018, 11:17:08 am »
Just to be clear: I didn't request Vaseline, that was 001.  I just suggested the spark gap test.  :D

If that's a concern for you, next time perhaps think more, post less? 

Not a problem for me. I think it was a good test, worth documenting.

So
I want to protect selector from arc at lamels
Is silicone best isolator than air?

If you think there might be an arc then grease isn't the answer (and probably won't help).

Change the operating procedure, wear protective gear, get a better meter if necessary.

I was wrong, it helped.  :-//

(on a simple spark gap)

...but I stand by the "If you think there might be an arc then grease isn't the answer" part.

(and if you're gonna apply grease, use grease that's designed for the job)
 
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Online Fungus

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Re: Handheld meter electrical robustness testing.
« Reply #2966 on: October 31, 2018, 11:32:08 am »
I was wrong, it helped.  :-//

I should probably qualify that:

a) Putting a big blob of non-conductive grease on a spark gap will obviously help. This was demonstrated.

My concern is that if you put it on the wiper contacts of a multimeter then it's going to get spread very thin after you turn the selector a few times. How effective will it be then? That's a lot harder to quantify - it depends on the meter.

b) The OP in the other thread seems to think a random applications of grease will make his meter safer. I don't share that view at all. I think he should buy a properly designed meter, one that won't arc in the first place.
 

Offline malagas_on_fire

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Re: Handheld meter electrical robustness testing.
« Reply #2967 on: October 31, 2018, 11:42:52 am »
Now it is using my old uni-t 50b and read the manual before using it. They are the acessible meters.
The one that i've got is the uni-t ut139A , the worst of the 139 line. At least it has ceramic fuses for the claimed voltage, it has enough grip and simple to use. It will be out of reach for modifications.

I've not looked at the 139A.  Just in general have not been very impressed with the UNI-T product line.  I still like that 210E clamp (as a clamp only). I'm not aware of anyone I know who bought one having any problems with it yet.  The 181A could also be a very nice meter with a few changes.

The uni-t 139A it should have in theory the same input protection as the 139C, but with less functions, counts, etc. The 210E  clamp meter was out of stock and i have already one clamp meter.  So far i'm quite happy with Eevblog BM235 since it has plenty of functions, good input protection , nice digits, decent backlight and battery life and that i use to monitor AC current which it is more accurate.

Edit Here is a picture of the actual meter with D.U.T.
« Last Edit: October 31, 2018, 12:04:32 pm by malagas_on_fire »
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Offline stj

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Re: Handheld meter electrical robustness testing.
« Reply #2968 on: October 31, 2018, 01:14:42 pm »
did anybody seriously think putting PETROLeum jelly on a spark-gap or switch would be a good idea??  :palm:
it's one of the primary ingrediants of a molotov coctail!!
 

Offline malagas_on_fire

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Re: Handheld meter electrical robustness testing.
« Reply #2969 on: October 31, 2018, 03:23:39 pm »
That would ignite the video of joesmith a lot, with possible flames :S Even the 230V 6V isolated mains does a little spark between 1mm or less on D.U.T. which is dangerous .
If one can make knowledge flow than it will go from negative to positve , for real
 

Offline floobydust

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Re: Handheld meter electrical robustness testing.
« Reply #2970 on: October 31, 2018, 05:32:39 pm »
There are many long, religious threads about lube in DMM rotary switches.
I'm experimenting with Krytox GPL 105.

It's basically liquid Teflon in a fluorinated-base. Used in Aerospace and MILSPEC.
No silicones, no petroleum, non-reactive, non-flammable. It's the best lube out there, but very expensive. Doesn't evaporate.
Oddly enough, it's used by car dealerships to stop weatherstripping from squeaking due to body flex.

Krytox 105 is a medium thickness oil and I think 205 is a grease.

 
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Offline stj

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Re: Handheld meter electrical robustness testing.
« Reply #2971 on: October 31, 2018, 05:33:22 pm »
they could spray the switch area with teflon and be done with it.
i cant see any point though.


grease actually makes sense.
if you think about it, the contact area is a thin line down the center of the pads,
so if you increase the gap from the space between the pads to the space between the centerline of the pads then you increase the breakdown voltage.
[in theory]
 
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Online 001

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Re: Handheld meter electrical robustness testing.
« Reply #2972 on: October 31, 2018, 07:19:32 pm »
Hi!

What is "High Voltage" actually?
Is it 200V, 600V or 1200V? DC or AC? What freq?
 

Offline Cliff Matthews

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Re: Handheld meter electrical robustness testing.
« Reply #2973 on: October 31, 2018, 07:26:20 pm »
What is "High Voltage" actually?
Is it 200V, 600V or 1200V? DC or AC? What freq?
https://en.wikipedia.org/wiki/High_voltage#Definition
 
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Online 001

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Re: Handheld meter electrical robustness testing.
« Reply #2974 on: October 31, 2018, 07:29:57 pm »
 


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