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 robustness testing  (Read 648781 times)

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Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #1000 on: September 12, 2016, 09:09:19 pm »
How much extra do you think it would cost Uni-T to build the new super meter?

(compared to the existing one)


I'm have no idea what their engineering costs are, cost to tool a new board, line setup, changing test fixtures, changing procedures, buying parts.....  Are they subsidized, what sort of pricing do they get .... Who knows.  It's not as simple as saying they just sprinkle a few parts in.  I would say your guess is as good as mine.   

I'm not sure what the super meter would even be.  I would start with the UT181A.  I doubt they sell any where near the qty as their low end meters like the 61 and 139 but that's by far the best meter I have seen them offer.   I would gladly pay another $50 for the UT181B that came with a spare battery pack, better materials for the LCD lens (scratch resistant),  more robust case design (I do like the looks of it), meet the EMC standards / more electrically robust,  added AC charger adapters, store the settings in the NVRAM, maybe add the 4-20mA as a percentage.   Just having the meter certified for both standards would be fairly costly.  The rest of what I would like to see is just fluff.  And to be very clear, for them not to try and reduce the bit of quality I am seeing in the 181A I have today! 

Really, I guess what I am suggesting is for them to make an effort to go after that Fluke 289.  The owner of the one I borrowed for that review really liked that UNI-T.  When I told him the price, he was floored.  Then again, could they sell enough to make back their investment? 

If they ever make the 181B, you can bet I will test it again.
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Offline Fungus

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Re: Handheld meter electrical robustness testing.
« Reply #1001 on: September 12, 2016, 09:17:22 pm »
How much extra do you think it would cost Uni-T to build the new super meter?

(compared to the existing one)


I'm have no idea what their engineering costs are, cost to tool a new board, line setup, changing test fixtures, changing procedures, buying parts.....  Are they subsidized, what sort of pricing do they get .... Who knows.  It's not as simple as saying they just sprinkle a few parts in.  I would say your guess is as good as mine.   

We already know they make different versions of their meters.

I'm not sure what the super meter would even be.

I mean the UT61E but with decent protection like the one you built. It has a decent chipset in it, it's a shame you can zap it with simple ESD.

 

Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #1002 on: September 13, 2016, 12:52:28 am »
How much extra do you think it would cost Uni-T to build the new super meter?

(compared to the existing one)


I'm have no idea what their engineering costs are, cost to tool a new board, line setup, changing test fixtures, changing procedures, buying parts.....  Are they subsidized, what sort of pricing do they get .... Who knows.  It's not as simple as saying they just sprinkle a few parts in.  I would say your guess is as good as mine.   

We already know they make different versions of their meters.

I'm not sure what the super meter would even be.

I mean the UT61E but with decent protection like the one you built. It has a decent chipset in it, it's a shame you can zap it with simple ESD.

Not working for them, I really would have no way of knowing what their costs are.  It's too bad that UNI-T does not represent themselves on this site like some of the other companies.  I'm sure several people would have questions/comments for them.   
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 #1003 on: September 14, 2016, 12:39:46 am »
The Tekpower Sunwa Sannuo Samwa Sunwei or Sanwa clone something or other YX-360TRE-B analog multimeter.  The box for this meter is marked Sunwa. 

Enjoy.



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Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #1004 on: September 15, 2016, 11:02:48 pm »
If the Tekpower Sunwa Sannuo Samwa Sunwei or Sanwa clone something or other YX-360TRE-B analog multimeter did not look bad enough already on the inside, I had a go at further improving it's robustness. 


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 #1005 on: September 16, 2016, 03:36:58 pm »
I have been looking at the manual for the EEVBLOG rebranded BM235.   Even if you don't own the meter, the manual is worth having a look.  Dave gives it his own personal touch.   :-+

Page 1 is a letter from Dave.  A couple of comments that caught my eye:

Quote
It's a beaut little meter, one of the safest and well built meters in a small form factor.
Quote
With the CAT IV rating (exceptional for this size of meter), you can feel confident and safe that you can use this meter on any high energy mains rated equipment in almost any scenario.

Under the general specification, it shows the meter meets EN61326.   Really, it looks pretty good.  What I would expect after running the BM869s.  It looks like they make some nice products.   

There are several nice photos starting on page 27.   It appears there are place holders for several small MOVs, RV1, RV5, RV6 RV7.   There also seems to two extra clamps (Q4,Q5 & Q6,Q7) that are not populated.    Last thing that stands out is it appears PTC1 is a smaller body than PTC2.   I believe any of the PTCs I have seen fail (breakdown) have been a small 5mm type.   I mentioned that when I attempted to harden the UT61E and replaced them.   
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 
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Offline SeanB

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Re: Handheld meter electrical robustness testing.
« Reply #1006 on: September 17, 2016, 06:48:19 pm »
Joe, you were wondering why they used 2 sets of batteries for the resistance ranges. The simple reason is that the 9V battery is not ( at least in the regular zinc carbon variety) able to supply 100mA or more, which is needed in the lower resistance ranges to drive the meter to full scale. Using a single ( in your one 2 AA cells so you have enough voltage to drive the LED and the buzzer, otherwise the regular version uses a single cell only)  AA dell will make it able to supply the required current for a long while ( at least long enough to measure 100 or so seconds at a time) without the terminal voltage dropping due to the cell internal resistance rising as it polarises internally with the reaction products. A 9V battery will polarise very fast at 100mA ,in the order of a second or so, but at 1mA or less it will take a long time.

Resistance readings you need to set the zero every time you change range, and do it again after every 100 or so readings as the batteries age and change terminal voltage. However these meters and others of the same type were very common in repair shops decades ago, and served very well to fix almost all equipment that came in. They however are not so useful now, just from the loading the constant current draw ( the ranges DC and AC are basically designed to draw a similar current at FS on each range, so they are pretty heavy loads on modern equipment) is not something you have to consider with a modern meter with a relatively constant high input impedance.

As to the AC range, those meters almost invariable are calibrated to read an average voltage with half wave rectified AC, but are calibrated so the scale reads RMS voltage instead. Thus on AC with DC applied they read high by around 30%, but for the use of checking transformer AC voltages this is fine. As well the AC voltage ranges are non linear at the bottom end, simply because they tend in modern meters to use a silicon diode, as opposed to the original use of a germanium point contact diode, with it's lower forward voltage drop. Basically AC voltage below 20% of full scale will be inaccurate, but that was often pointed out in the older manuals.

As to those extra diodes you added, very nice, I should add them to my old Hioki meter, as I have burnt a few resistors, funny enough pretty much those you cooked ;) in the years I have had it. Was new in around 1980 when I got it as a birthday present. Still use it as well.

You were wondering how they damp the meter movement from damaging itself, which is done using the aluminium former that the movement coil is wound on. This forms a shorted loop in the meter magnetic field, and thus provides a frictionless damping for the meter needle,  damping fast acceleration by being both an eddy current damper in the magnetic field of the magnet to fast angular acceleration of the needle, and also being a shorted turn in the transformer formed from the coil and conductive frame so reducing the effect AC current has on the meter movement. However the pivot mountings are the weak point, dropping the meter often either breaks the pivot off of the coil as the drop of shellac holding the pin there breaks, or it bends the pin and adds a massive friction load with the bent pin, or simply moves the coil into contact with the frame, or out of the linear portion of the gap field making the response less linear than it was.
 

Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #1007 on: September 17, 2016, 07:56:56 pm »
You were wondering how they damp the meter movement from damaging itself, which is done using the aluminium former that the movement coil is wound on. This forms a shorted loop in the meter magnetic field, and thus provides a frictionless damping for the meter needle,  damping fast acceleration by being both an eddy current damper in the magnetic field of the magnet to fast angular acceleration of the needle, and also being a shorted turn in the transformer formed from the coil and conductive frame so reducing the effect AC current has on the meter movement. However the pivot mountings are the weak point, dropping the meter often either breaks the pivot off of the coil as the drop of shellac holding the pin there breaks, or it bends the pin and adds a massive friction load with the bent pin, or simply moves the coil into contact with the frame, or out of the linear portion of the gap field making the response less linear than it was.

This is interesting. When I was searching old meter manuals, this never came up. I assumed this is what the small cap in parallel with the works was for.   Are you suggesting this technique was used for this particular meter?
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Online tautech

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Re: Handheld meter electrical robustness testing.
« Reply #1008 on: September 17, 2016, 08:07:07 pm »
Joe, movement dampening was used widely in AVO's, they had a 2 rotary dial UI and the movement is well dampened when the dial AC was in the Off position and the DC dial in the DC position.
Yeah sounds silly I know but it's well documented in the manuals and even on the meter backplate as for "Transit".
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Offline SeanB

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Re: Handheld meter electrical robustness testing.
« Reply #1009 on: September 17, 2016, 08:17:53 pm »
Very common on all d'Arsenoval movements as this method of damping is both very effective and very low cost to add to the meter during manufacture, plus it does not affect accuracy in any way at all in use.

You could get some very sensitive fast response movements which did not use the shorted eddy current turn, instead using a insulating slot on the former to make it undamped, and these were used mostly as mirror galvonometers in equipment like scanners, where they wound the movement to a higher current ( using a thicker wire) plus using a crossed coil to make the deflection depend on the current rather than force against a spring. Done more to get a good transient response so you could do XY scanning with 2 sets of coils orthogonal to each other, to drive a display very fast with some semblance of positioning accuracy. Damping on those was mostly by using a vane on the movement in the air to keep overshoot within limits, but they would still have a little oscillation around the balance point for step changes in coil current.

Putting the meter in DC current range for transit was also used on those meters with no dedicated position, the AVO had those 2 switch positions which meant the meter movement was shorted along with the eddy current winding, to provide extra damping of the needle during transit.
 
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Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #1010 on: September 17, 2016, 09:08:48 pm »
Even with the cheapest of analog meters, we still have an opportunity to learn something.  :-+   
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 #1011 on: September 19, 2016, 01:26:30 pm »
The EEVBLOG rebranded Brymen BM235. 

Also, I have updated the spreadsheet to include the BM235.

« Last Edit: September 19, 2016, 01:29:19 pm by joeqsmith »
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Offline 3db

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Re: Handheld meter electrical robustness testing.
« Reply #1012 on: September 19, 2016, 02:52:31 pm »
Nice review Joe.
This is the best review yet of the BM235, IMHO
I especially liked the reverse engineering of the input protection circuitry.
I also liked the comparisons with the other meters.
Thanks for the time and effort you put into your videos.

3DB  ;D
 
 
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Offline whitevamp

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Re: Handheld meter electrical robustness testing.
« Reply #1013 on: September 19, 2016, 07:32:03 pm »
nice review/testing oi the bm235
 
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Online tautech

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Re: Handheld meter electrical robustness testing.
« Reply #1014 on: September 19, 2016, 08:20:27 pm »
Joe, around 8 minutes in you show the pillar that's been modded to clear the PCB.
There were a couple of cracked inductors and Dave did a vid on the fault:
https://www.eevblog.com/forum/blog/eevblog-884-eevblog-bm235-multimeter-repair/
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Offline Muttley Snickers

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Re: Handheld meter electrical robustness testing.
« Reply #1015 on: September 19, 2016, 11:33:20 pm »
Hi tautech, after Joe showed the modification that Brymen had apparently done to the case mating sleeve by removing material I pulled my meter back apart to check and inserted a sliver of aluminium foil which is around 10 microns in thickness over the top of L3 and then put the meter back together and cranked up the screws with the batteries out just in case, after re-inspection there was no evidence on the foil that the sleeve was making contact with L3 on my particular meter.

As you mentioned after a recent component issue in that area perhaps Brymen felt that the clearance was insufficient thus their modification. My meter was one of the first sold and the case mating sleeve is intact and not modified as Joe’s appears to be.
 
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Offline Lightages

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Re: Handheld meter electrical robustness testing.
« Reply #1016 on: September 20, 2016, 12:09:19 am »
Nice review on the BM235 Joe. I am getting a little pissed off with Brymen though. the BM235 seems to have had a few small problems and then this quality control problem with the test lead jacks?

Except for that problem, the BM235 looks to be a great addition to the Brymen family. They certainly take safety seriously.
 

Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #1017 on: September 20, 2016, 03:43:11 am »
Nice review Joe.
This is the best review yet of the BM235, IMHO
I especially liked the reverse engineering of the input protection circuitry.
I also liked the comparisons with the other meters.
Thanks for the time and effort you put into your videos.

3DB  ;D

Thanks!  As usual, when I went back and watched it there are a few things I wish I would have changed.  For example, I frequently use the nS mode of the BM869s and never even mentioned it.  I also made a big deal of the UT61E being able to accurately measure 100Mohms but never brought it up.  Never mentioned the cost of the HIOKI......  Glad you are enjoying them. 
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 #1018 on: September 20, 2016, 04:27:13 am »
Hi tautech, after Joe showed the modification that Brymen had apparently done to the case mating sleeve by removing material I pulled my meter back apart to check and inserted a sliver of aluminium foil which is around 10 microns in thickness over the top of L3 and then put the meter back together and cranked up the screws with the batteries out just in case, after re-inspection there was no evidence on the foil that the sleeve was making contact with L3 on my particular meter.

As you mentioned after a recent component issue in that area perhaps Brymen felt that the clearance was insufficient thus their modification. My meter was one of the first sold and the case mating sleeve is intact and not modified as Joe’s appears to be.

Looking at the main half of the case (with the display) measuring the height of the lower lip to the upper lip, I get 0.165".  From the upper lip to the top of the boss measures 0.165".  From the top of the boss to the top of the PCB measures 0.412".     So, the lower lip to the top of the pcb is 0.412-2(.165)  or 0.082".    When the back case is installed (which has the batteries), the lower lips fits tight against the lower lip of the main case.  The mating boss on the back case is flush with the upper lip.   Measuring from the back case lower lip to the upper lip I measure 0.082".   So, the idea is that the back cases boss actually rests against the top side of the PCB.   

I would normally put some clay in there to measure it (or I like the dental stuff) but is seems that I can view the boss looking through the large fuse holder.  I attempted to get a picture of it but that's a real SOB to get in there with my camera and a light.  Attached are a couple of pictures showing the zero clearance.  That boss would touch off on L3.  You can see they were hand soldered.  I suspect they had some returns and thought it was a bad fillet, so add more solder and missed it was a clearance problem.  Good question for Brymen.  I'm fine with their short term fix. 

Also shown are two of the pictures I took showing the how the connector was not soldered flush to the PCB causing the offset in the bore.   
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Offline Muttley Snickers

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Re: Handheld meter electrical robustness testing.
« Reply #1019 on: September 20, 2016, 05:37:32 am »
I just had another look at mine and the female boss/ mating sleeve is making contact with the main PCB as you suggested but saturating the sleeve end with an engineering marker did not leave any recognisable imprint, the mating boss on the rear of my meter only just clears L3 laterally and it wouldn't take much to have it make contact and potentially have side pressure applied once the case was reassembled.

Excellent work and many thanks.   :-+
 

Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #1020 on: September 20, 2016, 05:47:09 am »
Good point!  I had not thought of that.  So the outside boss actually fits down beside L3. Does look like there could be enough clearance.   Wow, one wrong drop and there could be a fair amount of side loading as you suggest in that little bead.
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Offline Lightages

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Re: Handheld meter electrical robustness testing.
« Reply #1021 on: September 20, 2016, 04:49:46 pm »
I passed on the link for the video to Brymen. They said "As the poor installation of the input jack assemblies, I have informed our production to pay attention to it and improve it. Thanks for feeding back it to us. "
 

Offline joeqsmith

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Re: Handheld meter electrical robustness testing.
« Reply #1022 on: September 20, 2016, 11:43:17 pm »
With YouTube, one metric they provide is what external sites view your content.  You would think being such a small fish in the world of on-line videos, no one would care.  Yet some fairly large distributors and meter manufactures seem to visit from time to time. 
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 
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Offline Fungus

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Re: Handheld meter electrical robustness testing.
« Reply #1023 on: September 21, 2016, 08:24:42 am »
The EEVBLOG rebranded Brymen BM235. 

Brymen definitely seem to have some quality control issues there.

Misaligned posts (you'd assume the posts would be held in a jig while they were being soldered but apparently not), interference problems between the case+PCB. Dave has already done a couple of videos on fixing electrical problems from poorly chosen components (whining capacitor, LCD contrast).

It just shows how difficult it is to get everything right in production.
 

Offline spronkey

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Re: Handheld meter electrical robustness testing.
« Reply #1024 on: September 21, 2016, 08:55:13 am »
I passed on the link for the video to Brymen. They said "As the poor installation of the input jack assemblies, I have informed our production to pay attention to it and improve it. Thanks for feeding back it to us. "

Maybe the one Joe got was last off the production line on Friday :) I find it amusing that a company like Uni-T seems to have no trouble with quality of production, despite the shortcomings in design, yet Brymen seems to struggle a bit.

Just wanted to add thanks for all your work testing these meters Joe, really interesting to watch and learning a lot. Also great when looking to purchase some of these meters - especially the ESD type tests.

How much will the transient tests be wearing out the MOVs on these meters? It'd be interesting to see a test on a meter where the MOVs have worn out, and to see whether it changes the way the meter responds to transients.
 


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