Handheld meter robustness testing

[joeqsmith]

I made an attempt to change the light to give you a better idea of the wear.   The wiper and pads both look really good for 50+ thousand cycles.  This switch would need cleaning but I see no reason it would not last for several years with heavy use.   

The next step is to finally run a working meter.  I plan to start with something low end and see what we can learn from that. 

[joeqsmith]

One last picture showing a close up of the groove being cut into the mask.   

[joeqsmith]

It appears that this contact may have started to wear through.

[bitseeker]

I made an attempt to change the light to give you a better idea of the wear.   The wiper and pads both look really good for 50+ thousand cycles.

That they do. I wouldn't have thought it had endured that much.

It appears that this contact may have started to wear through.

Reminds me of tire chains.

[SeanB]

Thickness of plating shows up there Joe, thin plating and a thin brass backing wears faster. I have seen old equipment with a nice gold flashed heavy plate, must have cost at least $1 for that amount of selective plated gold on there, onto a nice German silver button, which in turn was brazes to a springy Beryllium copper spring member, running on another similar button. Of course these were aircraft switches, meant to be used for either heavy current, thus the german silver buttons, or for signal use, thus the heavy gold plate. They were specced for current down to 5mA and with a 20A maximum limit, either 28VDC or 115VAC. Not sure of how much they cost when new, but these not only had a lot number on them, in addition to the manufacturers part number, but also had serial numbers as well, plus a Made in France at the bottom.

[stj]

that's not good,
i would have expeced the outer part to have low friction because of the balls pressing it apart.
if that had been on the inside - i would understand.

[joeqsmith]

It could be coming from the inside.   It's hard to tell at this stage.  Like the test run, I don't plan to disturb the setup until it is finished.   

When I ran the damaged Kasuntest, it was very clear that designers need to consider how to run the traces out of the switch as the contacts can cut through the solder mask and through the trace.  Like every test I run, I suspect we are going to learn something from this free meter as well.   

Is the Brymen really going to come up short compared with the Flukes like people claim..... It's coming...    

[HalFET]

It'd be interesting to put a meter in a climate chamber and do some thermal cycling or 85°C/85%RH testing on it before testing the switch, that way it might corrode quite badly, which would certainly affect the reliability.

[IanB]

Our first working meter is not holding up very well.

Those cheap little HF meters have a very poor selector switch. They oxidize and show poor continuity after the meter has sat in storage for a while. I have sometimes picked one up to use and found it reading way off. The cure was to turn the switch a few times to clean off the oxidation and re-polish the contacts.

(This may be a reason why so few meters have a separate on/off switch. Putting the on/off switch on the rotary dial forces you to turn the dial before use and that keeps the contacts clean.)

As for the plastic dust, I'm sure it is the inevitable result of soft cheap plastic and continuous abrasion from turning the dial. The meter wasn't meant to take that abuse.

[joeqsmith]

I doubt I will do anything with the environment.  Not that it's a bad to look at salt, temp, humidity, thermal shock..... but it would require far more resources than I am willing to commit.  It may also be interesting to look at different lubrications, materials, thicknesses...  I am not trying to predict MTBF numbers for the designs rather I just want to know how they compare when ran to common set of rules.       

To cycle a meter will require a few days and I doubt we will see much of an effect from the changing environment.   The plan is to inspect the switch prior to attaching the test points and again after the meter is ran.   From this, along with the resistance, we should get a pretty good idea how the various meters compare with one another.   I am betting on there being a significant difference in them but again, I don't know.     

Like the transient tests, I'm sure we will see all sorts of comments on why the test is invalid when it is all said and done.  When the Fluke 101 outperformed the Fluke 87V by a large margin, it brought people out of the woodwork.       

[HalFET]

I doubt I will do anything with the environment.  Not that it's a bad to look at salt, temp, humidity, thermal shock..... but it would require far more resources than I am willing to commit.  It may also be interesting to look at different lubrications, materials, thicknesses...  I am not trying to predict MTBF numbers for the designs rather I just want to know how they compare when ran to common set of rules.       

To cycle a meter will require a few days and I doubt we will see much of an effect from the changing environment.   The plan is to inspect the switch prior to attaching the test points and again after the meter is ran.   From this, along with the resistance, we should get a pretty good idea how the various meters compare with one another.   I am betting on there being a significant difference in them but again, I don't know.     

Like the transient tests, I'm sure we will see all sorts of comments on why the test is invalid when it is all said and done.  When the Fluke 101 outperformed the Fluke 87V by a large margin, it brought people out of the woodwork.       

Heheh, people are never happy with testing! I got complaints that I tested a consumer oriented technology demonstrator using Mil. Std. 833 tests instead of bothering with the consumer test standards. But it seemed quite pointless to repeat the same test over and over again, only to see nothing would happen. The funny bit was that it perfectly survived 1000 cycles of being dragged from -65°C to 125°C, but still they felt the need to complain.

But anyway, if you want I can buy a couple of cheap meters, abuse them, and send them over. It ain't much work for to toss them into the corner of a climate chamber at work, more than enough space. I'm mostly curious in how it would de-rate the protection on the board.

[HalFET]

Actually we might now that I think about it, I'll check tomorrow when I'm in the lab. Might also be able to just measure the resistance while it's in the climate chamber if a few channels on the system are open. That could be a rather interesting test if I go and give it a good twist every hundred cycles or so.

[joeqsmith]

I would welcome seeing more independent destructive tests being ran on handhelds.   

[HalFET]

I would welcome seeing more independent destructive tests being ran on handhelds.   

Mhhh, we have a Chroma Hipot tester hanging around the lab and a safety cabinet for it as well apparently, 6 kV DC with a 10 mA trip current, and 5 kV AC with 30 mA trip current. Seems to cut out when it detects arcing though, so probably won't be very destructive on decent meters. I'll have to run by the health & safety person to get the key to this one I fear, but I'll give it a go. 

Could also already simply check the drift on its accuracy when exposed to those conditions. Can't imagine it'll do wonders on low-end meters.

[joeqsmith]

Drift would be a good one to look at.   I don't recommend switch cycling.  The Kasuntest continues squeaking.   

[stj]

what is the test?

fixed number of cycles?
fixed number of hours?
cycle till the switch falls apart? 

[joeqsmith]

what is the test?

fixed number of cycles?
fixed number of hours?
cycle till the switch falls apart? 

Inspect
Remove batteries as they are not used for this test.  Very carefully take meter apart as to not disturb contact area.  Document the switch area with a camera and note any lubrication.

Prep
Select contact and locate places where 30 AWG solid core wire may be attached at least one inch from switch to avoid any possible damage to switch pads.    Using about 6" of wire per test point.   Route wires outside of case without placing any strain on the case.  I have been going through the battery cover. 

Pretest
Attach external meter and measure the DCR with the switch closed.   Select which fork to use based on selector switch size.  Determine where to program the stepper to allow the function switch to fully rotate.   

Cycle
The switch is fully rotated both directions to complete one cycle.  Each switch will be cycled 50,000 times.  Note, if they are intermittent, I will continue to cycle them but if they go full open (1000 cycles with no resistance), I will abort the test.  If they grind to dust, I will continue the test as long as the switch continues to have some measureable resistance when closed.   

Final Inspection
Once the meters have been cycles, I will disassemble them and document my findings.  I plan to use the microscope to capture the problem areas.  I am interested in metal particulates trapped between the contacts and cut traces more than anything as these could pose a risk.   At this time, I have no plans to incrementally pull the meter down for inspection prior to fully completing the cycle test to avoid any contamination to the test.   

The software obviously records the contact resistance and I have a few different metrics that I plan to use to show how each switch wears. 

************************

This is a VERY LONG and time consuming test to run.  We are measuring fairly low resistance so the meter takes time to settle and you can't cycle the switch so fast that the plastic starts to warp or melt.  So it's the slow easy pace.

I wonder if the 17B+ will be useable after this many cycles.....

[HalFET]

Drift would be a good one to look at.   I don't recommend switch cycling.  The Kasuntest continues squeaking.

Drift testing would be easy enough. It's safe to presume that a calibrated Keithley 2001 is a good enough reference to work against. First victim has just been ordered: https:// m.aliexpress.com/s/item/32818141467.html

Heh I can imagine so. Try MIL-833 thermal shock for electronic assemblies, you could do it at home fairly quickly actually. Only issue is that it'd annihilate the LCD in these things most likrly.

[joeqsmith]

Your link did not work but item 32818141467 appears to be the UNI-T UT136B.   With as many UNI-T products I ran, I have never looked at this one. 

I have thought about making a small cooler for my cardboard/foam meat packing box.  This will be for fixed temperature testing.  I've ran some drift tests for people in the past where I set the box to an elevated temperature and hold it.   It would be nice to be able to run a sweep with it.  I have not thought about running any sort of controlled shock test.  Building some sort of dumbwaiter chamber would take far more effort than I would be willing to invest in a test like this.   

Good look testing.  As always, it will be interesting to see what you come up with.   


The Fluke was the forth meter I have attempted to measure the contact resistance with while life cycling the switch.  It has a long road ahead of it but I will say that the preliminary results are impressive.  Then again, it's being compared with a free meter, the ZT102/AN8002 and a blown up POS.      

My wife said I can't life cycle the original Fluke 101 I bought because it would be just wrong at this point.      It has survived everything I have thrown at it but I am still thinking to do some sort of high voltage shootout with the surviving meters at some point. Cycle testing this meter may damage it.  50,000 cycles takes days at the rate I am cycling them takes days, so there is plenty of time to decide.       

[Fungus]

My wife said I can't life cycle the original Fluke 101 I bought because it would be just wrong at this point.   

FWIW I agree. Do the 87V instead.

[joeqsmith]

My wife said I can't life cycle the original Fluke 101 I bought because it would be just wrong at this point.   

FWIW I agree. Do the 87V instead.

I am thinking about it.  87V fan boys have been commenting how well these meters hold up over time and question the life of the Brymen BM869s. 

Obviously, the old Schwinn bike has been around long enough to have some history compared with the new Giant with its Shimano shifters and Rigida rims.  We don't have a time machine, but we can accelerate the test.   If you want to take the personal fan boyism out of the equation, it only makes sense to grind the two meters into dust.   

Anyone want to loan me a brand new 87V to play with for a few days?? 

[kcbrown]

Anyone want to loan me a brand new 87V to play with for a few days?? 

If it fails, then it's still under warranty, right?   After all, the "normal wear and tear" exclusion wouldn't apply because this wear and tear would be anything but "normal", right?   

[Fungus]

Anyone want to loan me a brand new 87V to play with for a few days?? 

If it fails, then it's still under warranty, right?   After all, the "normal wear and tear" exclusion wouldn't apply because this wear and tear would be anything but "normal", right?   

I'd post it off to them just to see what they say.

50,000 turns isn't completely ridiculous though, eg. It's only 14 measurements a day for 10 years (assuming you switch on, measure, switch off). I bet a lot of people around here can beat that.

50,000 turns on something with a mid-2017 manufacture date,  I wonder if they'd spot it? 

[Fungus]

How about a Fluke 27 or something similar? From the days when rotary switches were made with real switches.



Bonus: It goes round and round forever. None of this left and right rubbish.

It would be interesting to see how they hold up electrically, too. This is one of Flukes first "robust" meters.

"Rugged safety features include extensive overload protection, high energy fuses, fused 10A range, and non-metallic cases and tilt bail. All voltage inputs recover or fail safe under power line surge tests for major feeders. This includes simulated lightning and load switching transient pulses up to 8 kV."

http://www.fluke.com/fluke/m2en/digital-multimeters/fluke-27.htm?pid=56055

[stj]

that's a nice waferswitch.
unfortunatly experience with old scopes show they will fail - by tarnishing usually.