Handheld meter robustness testing

[joeqsmith]

What's bigger than the Brymen BM869s?  The UNI-T UT181a!   There is not a lot of information about this meter.  This site has a few reviews of it and there are some pictures showing the insides which is what perked my interest in seeing one first hand.  So many PTC, MOVs, diode clamps.     The two 139s I looked at were damaged around 5KV.   By far one of the more robust UNI-T handheld meters I looked at.  When I received the UT210E and pulled it apart, again it appears they are actually making an attempt add protection.   This is a major change from the UT61D & E which had no protection.     

I started this thread with a bias against Fluke.  How that has changed....   When it came to UNI-T, my only bias was from watching videos, that is until I started testing them.  I went from no bias, to no clue, to their really bad, to their better than most, to WOW a mA DC/AC current probe that works for under $100!!     

I am not a big fan of the battery pack, but I was not a fan of Brymen putting that 9V transistor battery in the 869s.  It comes with the serial interface which the 869s did not.  It also came with a couple of K-types where the 869s came with only one.   It even has a little carry case.   The Brymen is UL listed.  Then I look at this 181 and there is an Intertek mark on it?! 

So here you go, 1st picture both meters showing AC+DC.  I am liking that tri-display, plus a digit here and there.   Looks like my original battery in the Brymen is finally starting to fail.

2nd picture showing both meters with 1 Volt DC off the Fluke.   

As much as I am not a fan of UNI-T (well except for the 210E) the little I have played with this 181A, I have to admit, I like it.  It's just the honeymoon. Give me some time with it.

[joeqsmith]

I get feedback on some of my meter videos that talk about the testing not being real world and how meters would never see these sort of conditions.  Recently, I had an opportunity to pull apart a power supply that had been hit with a real line transient.  So to be clear, not to the IEC or any other standard.   I then wondered what would happen if I ran the same power supply on my home made generators.   
 

[RobertoLG]

yeah that gives a pretty good idea, what could happen without some good input protection, even if your generator isn't that powerfull, now I'm curious about the new meter, looks like you wont pop this one    I like your videos too 

[Mark]

I was about to start a thread about the UT-171B vs the Brymen 869S so I am glad I saw your posts on the UT-181A.  I had fallen in love with the 181's huge easy-to-read screen but when I found out about the 2 update/sec rate I was so disappointed.  Is the update rate really that bad for such a modern meter? 
The 171B seems to be around 5/sec which is why I started looking at that meter as an alternative, but the niggly feeling that there is no such thing as a "high end UNI-T" remains...

[RobertoLG]

@ Joesmith

here is a teardown of my oldie, Motech MIC 2200 A, the pics aren't great quality, but I think you can have an idea, just tought you might be interested, ok? it probably wouldn't survive your tests lol

the only reference to the brand, but it's not the same meter, BKprecision got the multimeter part from Motech

http://www.radiomuseum.org/r/motech_digital_multimeter_mic_7s.html

Intersil 7106

[crispy_tofu]

I wonder if that's an ICL7106...

[joeqsmith]

@ Joesmith

here is a teardown of my oldie, Motech MIC 2200 A, the pics aren't great quality, but I think you can have an idea, just tought you might be interested, ok? it probably wouldn't survive your tests lol

the only reference to the brand, but it's not the same meter, BKprecision got the multimeter part from Motech

Thanks!  I like looking at old equipment and how it was built.  It's too bad that the LCD is cracked.     

I saw an old 80's digital hand held for sale local but they wanted about $40 for it with unknown condition.  Had the side slide switches. 

I was about to start a thread about the UT-171B vs the Brymen 869S so I am glad I saw your posts on the UT-181A.  I had fallen in love with the 181's huge easy-to-read screen but when I found out about the 2 update/sec rate I was so disappointed.  Is the update rate really that bad for such a modern meter? 
The 171B seems to be around 5/sec which is why I started looking at that meter as an alternative, but the niggly feeling that there is no such thing as a "high end UNI-T" remains...

    First let me say I have that same feeling about UNI-T.    You are not alone!!  This will be the eighth product I looked at from them and I am trying to keep an open mind.   In all honesty, I keep thinking "Please, what ever you do, don't fail that stupid ESD test!!!"       

There was a decent write up on this site about the 181A.   Have a look.     My plan was to basically follow the same review format I used to show the last six or so meters.   People seem to get more out of it rather than just stressing their inputs.   If you have something you would like to see with the 181, just let me know and I will see if I can set up a test for you. 

I may do that instead of playing with the 210E this weekend, so let me know.

[RobertoLG]

@ Joesmith

here is a teardown of my oldie, Motech MIC 2200 A, the pics aren't great quality, but I think you can have an idea, just tought you might be interested, ok? it probably wouldn't survive your tests lol

the only reference to the brand, but it's not the same meter, BKprecision got the multimeter part from Motech

Thanks!  I like looking at old equipment and how it was built.  It's too bad that the LCD is cracked.     

I saw an old 80's digital hand held for sale local but they wanted about $40 for it with unknown condition.  Had the side slide switches. 


it's not cracked, probably the seal failed, I tryed to seal it again with some vitral warnish, it's probably a manufacturing problem, never fell or anything like that, it works just fine, I don't have any precision reference, but I did compare it to the Digitek and it hasn't drifted to much, almost spot on

[saturation]

That's great research, Joe.  The Fluke patent is particularly interesting because that is now widely used by others, the plastic shields to supplement the creepage and clearances.  As for the RS patents, in the early days of DMMs, input protection varied from maker to maker, but the prime focus was avoiding damage due to incorrect settings such as measuring voltages on ohms range.  There was not much talk about impulses.

Once the IEC model for impulses on line voltage was agreed on, by 1992? CAT ratings were created, with a goal of user safety.  I think only Fluke continues to state their meters survive the CAT rating impulse while the IEC criteria don't specify the device be functional after a successful test.

Today, I don't think any DMM can survive the required maximum impulse for its CAT rating without externally added impulse protective devices.  However, your video series shows some DMMs can be designed to not only pass the CAT rating but also survive the rated impulses.

IIRC, some of your videos also show cheaper meters failing short of their CAT rating, while better brand meters being more consistent. 

However, the point of the protective devices is to protect the user first, not the DMM, for the specific CAT rating of the meter.

I would guess that most of the safety in hand held meters comes from the mechanics.   Things like spacing, wall thickness, double walled, etc.  Things like the GDTs, MOVs, secondary clamps, PTCs are there to protect the meter so it does not need to be replaced or repaired.   Maybe have a look at patents 5396168, 5606481, 5920188

[saturation]

I think Joe is doing everyone a great service, not only does he have the skills to play with kV, he gives a superb post mortem, repairs the meter quickly [if possible?], then subject it to more impulses.  Plus, more kudos for buying these meters himself to avoid patron bias, like a one man Consumer Report.

I don't think anyone on the net has demonstrated just what an impulse would do and compare it against other DMMs, than this series. 

IIRC the highest test impulse is ~ 12kV for CAT IV 1000V.  Joe's videos show test as high as 14kV or 15kV?
These are close enough to represent a slightly higher than CAT IV requirement for real world testing.

If the meter survives 15kV then all is well.  If not, one could bicker strictly speaking that its higher than the IEC requires.

In Fluke promo video, they show the 87V failing at 17kV, but making it past 15kV [ but they do not show a full functional test between and the test is only done on the V scale.]





Begins at 16:00

I get feedback on some of my meter videos that talk about the testing not being real world and how meters would never see these sort of conditions.  Recently, I had an opportunity to pull apart a power supply that had been hit with a real line transient.  So to be clear, not to the IEC or any other standard.   I then wondered what would happen if I ran the same power supply on my home made generators.   
 

[saturation]

Joe I think you clearly show how to remediate this meter to make it a true CAT III, and thanks for ID the other protective devices.  The Hioki is built very well, I just can't figure why they didn't go just a tiny bit more to give it the kind of impulse hardening you show can be done, fairly cheaply and easily too. 

[Fungus]

I don't think anyone on the net has demonstrated just what an impulse would do and compare it against other DMMs, than this series. 

Nope.

I get feedback on some of my meter videos that talk about the testing not being real world and how meters would never see these sort of conditions.  Recently, I had an opportunity to pull apart a power supply that had been hit with a real line transient.

The office where my missus works recently had some sort of power surge. It left their telephone switching board looking a bit like the PCB in your video.

[joeqsmith]

it's not cracked, probably the seal failed, I tryed to seal it again with some vitral warnish, it's probably a manufacturing problem, never fell or anything like that, it works just fine, I don't have any precision reference, but I did compare it to the Digitek and it hasn't drifted to much, almost spot on

That's too bad.   I have the second calculator I ever bought and it is slowly turning black as well. Maybe you could find a replacement LCD for it if you wanted to keep the meter.     

For home, I used to have a bunch of loose parts that I would use to check my meters.   I finally stuck them all in a box along with a non temperature controlled reference and a few other parts to aid in meter check out.  This has really helped me speed up my testing during these transient tests.

 

That's great research, Joe.  The Fluke patent is particularly interesting because that is now widely used by others, the plastic shields to supplement the creepage and clearances.  As for the RS patents, in the early days of DMMs, input protection varied from maker to maker, but the prime focus was avoiding damage due to incorrect settings such as measuring voltages on ohms range.  There was not much talk about impulses.

Once the IEC model for impulses on line voltage was agreed on, by 1992? CAT ratings were created, with a goal of user safety.  I think only Fluke continues to state their meters survive the CAT rating impulse while the IEC criteria don't specify the device be functional after a successful test.

Today, I don't think any DMM can survive the required maximum impulse for its CAT rating without externally added impulse protective devices.  However, your video series shows some DMMs can be designed to not only pass the CAT rating but also survive the rated impulses.

IIRC, some of your videos also show cheaper meters failing short of their CAT rating, while better brand meters being more consistent. 

I have a friend who worked for a company that made meters in the 70s.   He did a lot of repair work for them.  He was telling me about some of the meters that would get returned for repairs and some of the damage they had.      It makes sense back then that the main goal would be making the product survive.   

The testing the member had done after the first round of meters was done using a real generator.  This at least backed up what I found during my testing with the Fluke 101.   I try to be clear about what exactly I am doing when I run these test but was really happy to see someone attempt to repeat my results.      Because this test, IMO shows exactly what you stated.  A meter can be designed to not only pass but survive and in some cases survive far beyond what they are rated for!   

I had mentioned early on that I had spoke with a few companies about the IEC testing and how they interpreted the requirements.   In a nut shell,  Fluke was the one company that told me that they design the meters to survive the tests.   How the 87V fits into this I am not sure.   Too old a meter any they changed their goals perhaps.  It was a big surprise for me to see how poorly it performed.   Brymen was very upfront with me when I started to test the 869s.  That meter survived higher than they thought it would.   If I had a virgin one, I would repeat the tests to get a better idea what levels it can take.  Hioki was not too big of a surprise for me.  I have used their gear.  They know the environment and their products need to survive in it.   The Keysight was a disappointment but I was not too surprised after watching Dave's review.  His camera did a very good showing how that meter was built.   

[joeqsmith]

I think Joe is doing everyone a great service, not only does he have the skills to play with kV, he gives a superb post mortem, repairs the meter quickly [if possible?], then subject it to more impulses.  Plus, more kudos for buying these meters himself to avoid patron bias, like a one man Consumer Report.

I don't think anyone on the net has demonstrated just what an impulse would do and compare it against other DMMs, than this series. 

...

In Fluke promo video, they show the 87V failing at 17kV, but making it past 15kV [ but they do not show a full functional test between and the test is only done on the V scale.]

Thanks and glad your enjoying them.   We can't forget about 5KY's contributions as well!  Big thanks for giving me the opportunity to see just how much a Fluke 107 can take!!    

When I run that half cycle generator, the meters are placed in their VAC mode as well.  This seems to be the right thing to do for a test like this.     I can believe that the 87V without doing any sort of functional testing  and only using the VAC mode would not have a problem at higher voltages than the last one I looked at.   But, then what would be the point of the  test??     

Joe I think you clearly show how to remediate this meter to make it a true CAT III, and thanks for ID the other protective devices.  The Hioki is built very well, I just can't figure why they didn't go just a tiny bit more to give it the kind of impulse hardening you show can be done, fairly cheaply and easily too. 

 I'll tell you why.  They are trying to save me from having to build another generator!!     Really, I have no idea.   Maybe it would make it unsafe some how?   That's actually a pretty nice little meter.   

The office where my missus works recently had some sort of power surge. It left their telephone switching board looking a bit like the PCB in your video.

Hope no one was hurt.   I think most people involved with electrical and electronics are aware that events like this can/do happen.   

[RobertoLG]

yes I intend to keep the oldie( it was a gift from somebody very close), but here in brazil it's probably impossible to find a replacement for this LCD, now they started to sell rebranded Brymens here, but they prices are ridiculous, I probably could get a fluke cheaper,but now I can't afford jack...I hope in the near future I'll get at least one real good meter, but...
I'll take a look at my stuff, to see if I can put something togheter

and your videos really do a good service, they are a good reference for people, and thanks to that guy who donated the meters for to testing, a real nice gesture

[joeqsmith]

yes I intend to keep the oldie( it was a gift from somebody very close), but here in brazil it's probably impossible to find a replacement for this LCD, now they started to sell rebranded Brymens here, but they prices are ridiculous, I probably could get a fluke cheaper,but now I can't afford jack...I hope in the near future I'll get at least one real good meter, but...
I'll take a look at my stuff, to see if I can put something togheter

and your videos really do a good service, they are a good reference for people, and thanks to that guy who donated the meters for to testing, a real nice gesture

Wow, the Flukes are less expensive than Brymen!  That's a twist! 

It was a real nice gesture when 5ky (TechnologyCatalyst on youtube)  agreed to donate those meters.   I doubt very much I would have continued to test meters had it not been for that.   It also forced me to come up with a better way to test them and to start publishing the results.   It was a big win for the few people who are following along.   

Weekend is here and I have a UNI-T calling my name.....

[RobertoLG]

yes I intend to keep the oldie( it was a gift from somebody very close), but here in brazil it's probably impossible to find a replacement for this LCD, now they started to sell rebranded Brymens here, but they prices are ridiculous, I probably could get a fluke cheaper,but now I can't afford jack...I hope in the near future I'll get at least one real good meter, but...
I'll take a look at my stuff, to see if I can put something togheter

and your videos really do a good service, they are a good reference for people, and thanks to that guy who donated the meters for to testing, a real nice gesture

Wow, the Flukes are less expensive than Brymen!  That's a twist! 

It was a real nice gesture when 5ky (TechnologyCatalyst on youtube)  agreed to donate those meters.   I doubt very much I would have continued to test meters had it not been for that.   It also forced me to come up with a better way to test them and to start publishing the results.   It was a big win for the few people who are following along.   

Weekend is here and I have a UNI-T calling my name.....

kinda strange really, the Brymens are rebranded by Minipa, they sell cheaper meters, they have a big "line" of rebranded chinese meters, that I really doubt that they match the CAT ratings printed on them, some are  unfused  , there are other brands, but I wouldn't say they are safe, but man, you got me going on that Hioki, now I want one 

now maybe they are few, but like TheRadioTech started with few people and now has almost 1000 subscribers, continue and more and more people will start to follow 

[saturation]

Yes, mea culpa thanks to TC for providing the meters!

Your generator remains impressive, early in this thread Meter Junkie shows the Fluke 101 using an industrial quality one which is in $5k range, to start, I think the video shows a MegaPulse by Compliance West. 



For the rest of us, one can do limited tests using much easier to access and afford kV sources like a hipot tester or an electrophoretic supply.

Given your generator, setup, and interest, keep on testing! 

An idea, you could show how good older branded meters are, or not, on their impulse resistance.  There are many pre-CAT and older CAT rated meters sold on Ebay. 

Fluke 23, 25, 77, 8021, first generator 80s series, HP and Tektronix DMMs, Craftsman, Micronta, Beckman Industrial etc., as well as Japanese meters from the golden era such as Hioki, Sanwa, Yokogawa [ that were made in Japan.]

Also you can extend your tests to dielectric withstand of the chassis to the PCB, particularly in older meters, which could have deteriorated over time.

Thanks and glad your enjoying them.   We can't forget about 5KY's contributions as well!  Big thanks for giving me the opportunity to see just how much a Fluke 107 can take!!    

[joeqsmith]

Imagine having a generator like that at home!  My concern would not be so much from dieing of electrocution but from my wife.   

I had thought about using a Hi-pot tester early on when I was trying to think of how to benchmark them.   My concern was that it would not represent an actual transient condition and with it being such a low energy, it may not allow me to sort them out.  It would be interesting to see someone running some different tests in parallel but there is a fair amount of cost and time involved.    There is a guy on youtube that has done a lot of meter reviews and he talked about running some test like this but in the end never did any more with it.   

I would be all for testing a few older meters for fun but sourcing them is a problem.  I have not had an eBay account in maybe 10 years.  People will comment how they trust their old ..... meter on mains.  Fluke will tell you otherwise in many cases.   

Well, break time is over.   Shooting video today so again, if anyone wants to see something specific with the 181A, now is the time to ask.  Meters don't typically live very long in my hands.
 

[joeqsmith]

The original review showing the internals of the 181A:

https://www.eevblog.com/forum/testgear/uni-t-ut181a-pictures/

Spent the day using the meter.  The update rate does appear to be 2Hz regardless of the range.  I would have thought with the lowest resolution range, the update rate would increase but it appears to remain fixed.  A little strange is that the bar graph is actually updated at a fairly good rate.   That said, for me personally the 2Hz is not that big of a deal but I did send UNI-T an email about it.     

Hope to have the first part upload it in the next day or so.         

[joeqsmith]

The UNI-T UT181A gets no special treatment....   Video is long, so grab some popcorn before you load it up.

[Maxlor]

Heh, the end of that is rather anticlimatic. It'd be really disappointing if that's all it takes to kill that meter. I'm hoping and guessing that it's the soft power feature that's causing the issue there (why do manufacturers feel they have to add soft power on high end meters?)

Btw, one thing you mention in nearly every video is the term FWHH, but I don't understand what that means. Maybe you explained it already somewhere, but I missed it? If not, maybe you could show a scope trace of what it means exactly if you find the time.

[RobertoLG]

  dead with one hit??? yeah that old saying is always right, when it looks too good... I'm really disapointed, I tought it would perform better tha that, but the video was excelent

[smithnerd]

The old Uni-T Achilles heel. 

[joeqsmith]

Heh, the end of that is rather anticlimatic. It'd be really disappointing if that's all it takes to kill that meter. I'm hoping and guessing that it's the soft power feature that's causing the issue there (why do manufacturers feel they have to add soft power on high end meters?)

After the video, I pulled both batteries and reinstalled.  It's dead. Disappointing yes but typical for that brand. 

Btw, one thing you mention in nearly every video is the term FWHH, but I don't understand what that means. Maybe you explained it already somewhere, but I missed it? If not, maybe you could show a scope trace of what it means exactly if you find the time.

If you look up full width half maximum you would find it.  The width of the pulse at half the height.    So if I use a 1KV pulse, that is 1KV peak, and at 500V if you measured the width, you would have in my case, 100us in most cases.   If I call out a 2 ohm source, that's the impedance from the generator to the meter. 

dead with one hit??? yeah that old saying is always right, when it looks too good... I'm really disapointed, I tought it would perform better tha that, but the video was excelent

Yes, just that one hit damaged it.   But data is data and there is no reason to try and sugar coat it.  Glad you enjoyed the video. 

The old Uni-T Achilles heel. 

Three of the five that failed this were UNI-T.  This was a test I really thought was a waste of my time to even run as that starter is not much of a pulse.   

I was asked about the pulse it put out.  This is a little difficult to say as I really do not have the equipment to measure it.   Static discharges will typically have <1ns rise times and their decay in in the 10s of ns.   Then there is a lot of current and noise that loves to corrupt the measurement. 

In this picture, I show a couple of home made targets I put together a to attempt to measure the pulse.   These discs are FR4 and there are several 1206 resistors that are embedded inside of it to attempt to minimize the inductance.


...

Sorry, I looked and have no scope shots of the data I took from it.