UNI-T UT61E First Problem...

[hgg]

Hi guys,

First problem with the chinese UT61E multimeter...

I received today a 10W 20V/0.5A solar panel and I tried to test it using the UT61E.
The leads were connected and the output voltage was 20.6V, fine.  Then I tried to
measure the current at short circuit with no load.  I switched the leads of the UT61E
to current and the scale to mA.  When I connected the probes to the solar panel,
the meter made a fast beep beep sound and it did not display any current output.
When I turned it off and on again, it showed the current ok but the symbol of the
serial data transfer appeared on the display...  It is always on now, I cannot turn
it off.  I tried the serial connection to see if it transmits data and it works fine.  The
problem is that it looks like that the data mode is always on and I am afraid it will
drain the batteries fast. 

What could have happened?
Anybody else with a similar problem?

Thanks.

[Monkeh]

The data mode is always on. You were never able to turn it off.

Shorting current sources through your meter is a bad idea.

[hgg]

Hi,  I thought that it was on only when you connect the data cable.
What is wrong with connecting a low current solar panel like that?

[sync]

Why do you put a 500mA source on the UT-61E mA input? It's highest range is 220mA. You simply overloaded it and it beep to warn you about this.

[hgg]

You are right, I am not thinking today...   

[seanspotatobusiness]

Why do you put a 500mA source on the UT-61E mA input? It's highest range is 220mA. You simply overloaded it and it beep to warn you about this.

I have a UT61E and it came with a 1A fuse in it. Why would it have a 1A fuse and a limit of 220 mA?

[janoc]

I have a UT61E and it came with a 1A fuse in it. Why would it have a 1A fuse and a limit of 220 mA?

Because the fuse is there to protect the meter from you blowing it up and not to "clamp" the current to the maximum value the meter is able to measure?

It probably can withstand more than 220mA just fine, but higher currents go over the working range of the ADC, that's all. If I was you I would be glad for the 1A fuse, because having to replace it whenever measuring over 200mA would really suck. Having to measure everything at the 10A range would be no fun neither.

[joeqsmith]

The 61E 5KY sent me along with the one I now have both came with a 1A fuse as well.   The circuit board is screened 1A.  The high res pictures for the GS marked version show 0.5A 600V fuse. 

[sergiusora]

Hello!
I fried my UT61E, over voltage on voltage measure, the problem is that i was careful to set max range and i was not expecting more then 600v, now when i power it beeps intermittent and no display on lcd.

no visible blown parts only a little smoke on the commutator side (see image).
What can i do to fix.

[joeqsmith]

I would just buy a new one.  I've damaged a few of these with over voltage.  In all cases the control IC was damaged.  I doubt you could get a replacement part cheaper than what the meter would cost.  I've put some fairly high voltages into them without a problem.  Any idea what voltage the meter saw?

[sergiusora]

i measured across a ultrasonic welder,  something similar with this one.
The driver for this is powered with 220V  rectified and filtered (~350Vcc), there is a ferrite transformer that might be a booster?
I cant find the IC (ES51922A) will buy a new multimeter .

[joeqsmith]

Thank you for the update.   

I have seen these in use but I've never looked into the details.   I've damaged a lot of UNI-T products with nothing more than a small piezo grill igniter.  This is a very low energy, sub 5ns pulse.   I can believe something with your welder could indeed damage a UT61E where a better meter may have survived.    You may have stumbled onto a real world low energy high voltage test case at the expense of your meter.     

If you don't mind, please provide the manufacture and part numbers for the head and supply.   I would like to dig into this in a little more detail.  It could be something unique to your setup. 

[sergiusora]

its a part of a fabric quilting machine from china, similar to this: https://www.alibaba.com/product-detail/Ultrasonic-quilting-machine-for-polyester-fabric_60224326101.html
i was there just to try fix it (one of the horns not working), i do not have more specific details.

[Fungus]

If you're going to buy a new meter it might be worth considering something a bit more robust, eg. A Fluke 15B+/17B+.

[janoc]

Indeed - if the meter blows up because of overvoltage, I do wonder how did it pass its certification tests (where it needs to withstand test voltages of several kilovolts)? Does it have any input protection at all? For a $100 class meter I would expect better, IMO.


Either one of those Flukes or even the Brymen 235 (the one Dave is selling) would likely be a much better choice. And it is only a little more expensive than that UNI-T meter.

[joeqsmith]

its a part of a fabric quilting machine from china, similar to this: https://www.alibaba.com/product-detail/Ultrasonic-quilting-machine-for-polyester-fabric_60224326101.html
i was there just to try fix it (one of the horns not working), i do not have more specific details.

Thanks.  It's still good for people to be aware of. 

Indeed - if the meter blows up because of overvoltage, I do wonder how did it pass its certification tests (where it needs to withstand test voltages of several kilovolts)? Does it have any input protection at all? For a $100 class meter I would expect better, IMO.

There are different versions of the 61E.  Some certified, others I suspect are not.   The tests you mention call for a specific waveform.  This will not be what the OP was attempting to measure.    I see a lot of meters survive with peaks well above 10KV but that doesn't mean a meter would survive hooked to the 2KV output of a MOT.   Details...     I am sure the 87V was certified to the IEC safety standards.  As we have seen, it does not mean that it can survive a low energy high voltage hit as we have seen with so many meters.   In the case of the 87V, these were the highest cost Flukes I looked at and it performed the worse by a large margin over even the least expensive meter Fluke offers.   

Again, this is why I like seeing the equipment pass the EMC as well as the safety standards.

[janoc]

Well, that meter is supposedly rated CAT III 1000V and CAT IV 600V.

According to this document from Fluke:
http://content.fluke.com/promotions/promo-dmm/0518-dmm-campaign/dmm/fluke_dmm-chfr/files/safetyguidelines.pdf

Such meter should be able to withstand a transient of 8kV for 20 repetitions, from a 2 Ohm source. Surely the OPs gadget is unlikely to produce larger/more energetic transients than that?

But given the teardown pictures here:
https://www.eevblog.com/forum/testgear/uni-t-ut61e-multimeter-teardown-photos/

and here:
https://www.markhennessy.co.uk/budget_multimeters/unit_ut61e.htm

and the German version:
https://www.eevblog.com/forum/index.php?action=dlattach;topic=3391.0;attach=128053;image

I don't believe that that meter has been actually tested to those limits apart from maybe the German version. The CAT ratings are obviously BS.

The input protection are only two piddly PTCs and two ceramic fuses. There are no large protection resistors, no MOVs, no safety slots or blast barriers (well there is something looking like a short one), the meter uses those crappy split input jacks, etc.

There is a supposedly safer EU version (the second link) that has 3 PTCs and an isolation slot cut under them. The German one has 3 MOVs and upgraded fuses.

I believe that the OP has the Chinese version without any MOVs and with only the two PTCs, because there is no isolation slot under them (matches the first teardown).


Now compare to the BM235:


PTCs, MOVs, huge protection resistors, input jacks are solid and properly insulated/blast shielded, there are safety slots everywhere, etc. And that is a meter that is only slightly more expensive (the UT61E is sold for ~80-100 euro from outfits like Batronix).

The Uni-T meter could be a superb meter for low voltage electronics but going near anything high power with it is asking for a Darwin award, IMO.

Various fanboys are jumping up and down in rage about supposed elitism of people who recommend expensive brand name meters even for hobbyists every time the discussion comes up but I think the OP's situation is a perfect illustration of why.  Even a hobbyist might need a safe meter that actually is able to fulfill the ratings stated on the box. One never knows when that extra safety will save the day. The OP relied on those (that should be good enough, right?) in this case and kaboom. Good that only the meter has died this time ...

[joeqsmith]

Searching the PDF for 20 and rep, I could find no such reference.  They do use the term withstand but I don't see where they define it.  I sounds like you feel this means that the meter is not damaged but I do not know if this is Fluke or IECs intent.    The 8KV they mention has a specified rise time.  I have shown where fast edge transients will damage many UNI-T products.  The videos were in that first link you provided.   I doubt the resistors, MOVs and PTCs will do much for safety.   I suspect the GS version you mention would still fail the ESD tests.   I don't believe they certify for the EMC standard, only safety.  It's this weakness  that I suspect is the reason the OPs meter was damaged.  But that's just a guess on my part.

[janoc]

Searching the PDF for 20 and rep, I could find no such reference.  They do use the term withstand but I don't see where they define it.  I sounds like you feel this means that the meter is not damaged but I do not know if this is Fluke or IECs intent.    The 8KV they mention has a specified rise time.  I have shown where fast edge transients will damage many UNI-T products.  The videos were in that first link you provided.   I doubt the resistors, MOVs and PTCs will do much for safety.   I suspect the GS version you mention would still fail the ESD tests.   I don't believe they certify for the EMC standard, only safety.  It's this weakness  that I suspect is the reason the OPs meter was damaged.  But that's just a guess on my part.

Table 2 on the last page. The 8kV test voltage is part of the IEC standard, it is not something that Fluke has invented (same info is e.g. here: http://www.transcat.com/media/pdf/Multimeters.pdf ). Unfortunately the relevant EU norm text (UK version - BS EN 61010-1:2010) is some 300 bucks to obtain

The MOVs and PTCs will not deal with ESD safety (they are too slow for that) but that meter has also clamping diodes. A zap from a well charged human finger in the dry winter air can be tens of kilovolts - if the meter had ESD issues it would be dying in normal use too. And if the meter is not EMC compliant, how can it be legally sold in EU (not speaking about eBay imports and such)? EMC compliance is a mandatory  part of CE, so in that case Uni-T or the importer are fraudulently declaring the CE compliance. I have also my doubts that even the German, GS version, passes the claimed CAT IV 600 tests given how is the input part designed, but I am not an expert on that.

Something is pretty fishy here.

[joeqsmith]

Table 2 on the last page. The 8kV test voltage is part of the IEC standard, it is not something that Fluke has invented (same info is e.g. here: http://www.transcat.com/media/pdf/Multimeters.pdf ). Unfortunately the relevant EU norm text (UK version - BS EN 61010-1:2010) is some 300 bucks to obtain

You are correct.  Funny the search engine does not find that header and I was too lazy to read it.  Did you find where they define what withstand means?  Do you feel a handheld meter must be functional after what ever tests they put it through?     

The MOVs and PTCs will not deal with ESD safety (they are too slow for that) but that meter has also clamping diodes. A zap from a well charged human finger in the dry winter air can be tens of kilovolts - if the meter had ESD issues it would be dying in normal use too. And if the meter is not EMC compliant, how can it be legally sold in EU (not speaking about eBay imports and such)? EMC compliance is a mandatory  part of CE, so in that case Uni-T or the importer are fraudulently declaring the CE compliance. I have also my doubts that even the German, GS version, passes the claimed CAT IV 600 tests given how is the input part designed, but I am not an expert on that.

Something is pretty fishy here.

I am not aware on any ESD safety concerns.  ESD testing falls under EMC not the safety standards.   The PTCs may provide some current limit but you are correct that their thermal response is too slow to do anything.  The capacitance of the MOVs may also help.  The layout will play a big part in it as well.   I've shown in detail what I did to the 61E for ESD and why.  I am surprised UNI-T has any problems with ESD as they obviously can produce products that are fairly immune.

I've shown where some meters I've looked at were certified for safety only where other are also certified for EMC.  Most of the meters I have looked at have no third party certification.   I have no idea what is legally required in order to sell a handheld meter in the EU. 

The reports are free to download and you should be able to look them up.  I have found some UNI-T products they have had certified, for example the AMPROBE AM510.  I would not be too surprised to find the GS version of the UT61E was indeed certified by a third party.  For me personally, I have little interest in safety when it comes to handheld meters and more so their ability to survive under various conditions. 

[janoc]

Table 2 on the last page. The 8kV test voltage is part of the IEC standard, it is not something that Fluke has invented (same info is e.g. here: http://www.transcat.com/media/pdf/Multimeters.pdf ). Unfortunately the relevant EU norm text (UK version - BS EN 61010-1:2010) is some 300 bucks to obtain

You are correct.  Funny the search engine does not find that header and I was too lazy to read it.  Did you find where they define what withstand means?  Do you feel a handheld meter must be functional after what ever tests they put it through?     

No, I haven't found that (it is likely only in the $$$ norms - I do fail to get how a mandatory norm can be that expensive!). However, I did find some testing manuals that say that current is being measured during that testing and if the current suddenly goes up after the initial stabilization period (to let any capacitances charge), e.g. because of insulation breakdown or sparking, the device will fail the test, regardless of whether or not it still works afterwards.

So I would have expected in the OP's case a test failure - there is no way a spark causing that blackened switch wouldn't have been registered.

I am not aware on any ESD safety concerns.  ESD testing falls under EMC not the safety standards.   The PTCs may provide some current limit but you are correct that their thermal response is too slow to do anything.  The capacitance of the MOVs may also help.  The layout will play a big part in it as well.   I've shown in detail what I did to the 61E for ESD and why.  I am surprised UNI-T has any problems with ESD as they obviously can produce products that are fairly immune.

I've shown where some meters I've looked at were certified for safety only where other are also certified for EMC.  Most of the meters I have looked at have no third party certification.   I have no idea what is legally required in order to sell a handheld meter in the EU. 

The reports are free to download and you should be able to look them up.  I have found some UNI-T products they have had certified, for example the AMPROBE AM510.  I would not be too surprised to find the GS version of the UT61E was indeed certified by a third party.  For me personally, I have little interest in safety when it comes to handheld meters and more so their ability to survive under various conditions.

Sorry, I meant "ESD safety" in the sense that the device doesn't break, not in the sense that it could be unsafe for the user. Poor choice of words on my side.

For selling a meter (or anything electronic, in fact) in the EU the manufacturer or importer must declare compliance with the low voltage directive:
http://ec.europa.eu/growth/sectors/electrical-engineering/lvd-directive_en

In fact, multimeters are explicitly dealt with in that directive, citing the IEC 61010.

And also the EMC directive:
http://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32014L0030

Compliance with those two is required if you want to declare your device to be compliant and apply the CE mark - which is a precondition for being allowed to bring the device to the market.

Now, the problem is that CE is self-certified, so you are not really required to do any testing, only deliver a "Declaration of conformity", which is basically a piece of paper saying that the device is compliant with the relevant norms. On the other hand, if a problem is found and you don't have the paperwork proving that the device really is compliant in order, you are going to be in a world of pain. That's the opposite of the US system where you must pass the mandatory FCC certification before you can start selling your gadget.

Of course, any Chinese eBay or AliExpress sellers will not obey these, it is the problem of the person importing the device. But that's why I have been citing e.g. Batronix which is selling this meter in the EU. If the meter has EMC or safety issues, then Batronix could be in trouble if they are the importer providing the required declaration of conformity. I don't know whether that's the case.

But check the pictures of the meter on the Batronix site:
https://www.batronix.com/shop/multimeter/multimeter-ut61e.html



The meter there claims CAT II 600V and CAT III 300V only, unlike the CAT IV 600V on the Chinese one. Could it be that it simply couldn't pass those original requirements even with the extra protections and the ratings were a total BS? CAT II 600V and CAT IV 600V is an enormous difference.

So this is a meter that has no place anywhere near 380V three phase gear, IMO (which is what the OP was attempting to repair). However, even CAT II 600V must withstand the 4kV test voltage ...

[Fungus]

But check the pictures of the meter on the Batronix site:

The meter there claims CAT II 600V and CAT III 300V only, unlike the CAT IV 600V on the Chinese one. Could it be that it simply couldn't pass those original requirements even with the extra protections and the ratings were a total BS? CAT II 600V and CAT IV 600V is an enormous difference.

Yep. This version has extra safety components and a realistic rating.

the ratings were a total BS?

This should be well known by now. 

[SeanB]

Ultrasonic welder expect a working piezo to have 4kv or more on it, and a cracked one even more with a semi functional power driver as the capacitance is reduced when it cracks into bits internally. There is a reason the power leads are insulated to 10kV and encapsulated, you have to drive a very high impedance load and it also has high capacitance, so expect high voltages and high peak currents as well. Simplest test method to see if it is working is a small wire loop and a scope near the cables, it picks up the radiated energy quite well from 5cm away.

[janoc]

Ultrasonic welder expect a working piezo to have 4kv or more on it, and a cracked one even more with a semi functional power driver as the capacitance is reduced when it cracks into bits internally. There is a reason the power leads are insulated to 10kV and encapsulated, you have to drive a very high impedance load and it also has high capacitance, so expect high voltages and high peak currents as well. Simplest test method to see if it is working is a small wire loop and a scope near the cables, it picks up the radiated energy quite well from 5cm away.

 Uh oh ... Well, if that's the case, then measuring across that piezzo was really asking for a Darwin award, even with a much better meter than the Uni-T junker.

The photo posted by the OP didn't look like it had some serious high voltage insulation, though - unless someone has removed it already.

[joeqsmith]

I wouldn't expect it would be directly across the piezo and the driver to be fairly low voltage.   I assumed it would have a transformer in the head to drive the piezo.   This is why I brought up the grill starter and asked for specific part numbers.    I wouldn't call it a Darwin award by any means.  It's fairly low energy and I would have thought normally not enough to damage a meter.  But again, I have shown the problems with the UT61E when looking at fast edge transients.  Well, and other UNI-T products as well.. 

[janoc]

I wouldn't expect it would be directly across the piezo and the driver to be fairly low voltage.   I assumed it would have a transformer in the head to drive the piezo.   This is why I brought up the grill starter and asked for specific part numbers.    I wouldn't call it a Darwin award by any means.  It's fairly low energy and I would have thought normally not enough to damage a meter.  But again, I have shown the problems with the UT61E when looking at fast edge transients.  Well, and other UNI-T products as well.. 

Well, seriously, that meter being used on a 380V three phase installation would be asking for a Darwin award regardless of whether or not there is only a low voltage on the piezzo. Imagine a ground fault or a high energy mains transient (definitely not unheard of in a factory) on that machine while the sparky is poking around with that Uni-T meter. That's a straight CAT III environment vs a meter with an insufficient input section and fake safety ratings. People have died because of such combination.

That these meters "pop" simply because of ESD is only an icing on the cake ...

[seanspotatobusiness]

Can I use the Uni-T UT61E to measure the output of a laptop CCFL inverter? I'm not sure what the voltage is but it's at least several hundred volts. Could it be over 1000 V? Perhaps I can make a potential divider and measure across that?

[stj]

inverters can be anything from 300 to several thousand volts - and they vary with lamp temperature because they are current-regulated.
i wouldnt go near one with a meter - btw, the probes may load the circuit and mess up the feedback resulting in a shutdown.
also, they run at very high frequency's - so most meters wouldnt show much anyway.
you really need a scope with a x100 or x1000 probe.

if it's not working,
check the fuse, the fets, and compare the transformer windings to a known good one. (lucky they usually come in pairs)

[joeqsmith]

Why do you feel looking across the head is a CAT III environment?   Do you really feel the OP was at risk of death making this measurement from a line transient?  If so, why?

[janoc]

Why do you feel looking across the head is a CAT III environment?   Do you really feel the OP was at risk of death making this measurement from a line transient?  If so, why?

The OP posted the machine this was in is an industrial three phase installation. That is about as CAT III as it gets, IMO. That the head itself is not connected directly to the mains is not really that relevant there - the machine was obviously on, connected to the mains when he was doing the measurement, no? Unless the circuit is transient protected or powered from a low energy transformer limiting the potential exposure, I would rather err on the side of safety.

Also he was unlikely measuring only that head in that machine - I doubt an electrician would carry a good meter for measuring the dangerous stuff and then whip out a second crappy meter for the "safe" parts of the machine.

For the record, I was referring to the table 1 in this document:
http://content.fluke.com/promotions/promo-dmm/0518-dmm-campaign/dmm/fluke_dmm-chfr/files/safetyguidelines.pdf

[joeqsmith]

I'm not disagreeing with you but am interested in when you feel you need to treat it as a CAT III environment and if you felt the OP was at risk of death from attaching the meter across the head like they mentioned.  If you really feel the potential hazard is at this level, I am curious do you treat all low voltage equipment (PLCs and such) as CAT III if they are part of a hard wired 3P system? 

Not being there, I really have no idea what else they were probing beyond what they claimed.  I doubt that it was just the head as well but I don't know. 
I don't know how the system is wired inside or whats upstream. 

[janoc]

I'm not disagreeing with you but am interested in when you feel you need to treat it as a CAT III environment and if you felt the OP was at risk of death from attaching the meter across the head like they mentioned.  If you really feel the potential hazard is at this level, I am curious do you treat all low voltage equipment (PLCs and such) as CAT III if they are part of a hard wired 3P system? 

Not being there, I really have no idea what else they were probing beyond what they claimed.  I doubt that it was just the head as well but I don't know. 
I don't know how the system is wired inside or whats upstream.

I was more thinking about doing the measurements on that machine in general with that type of meter as asking for the Darwin award, not specifically about the ultrasonic horn. At least until SeanB mentioned that it could have up to 10kV on it (which the meter certainly won't handle gracefully) with the possibility of high peak currents (so probably some significant energy could happen there).

Re handling the PLCs and similar - that actually depends. If the PLCs are behind a well protected low voltage power supply in a separate cabinet, then that would likely qualify as CAT I (at least according to that Fluke's document).

However, it is fairly common to see cabinets that have both mains and 24V in them (e.g. the power supplies, breakers and the PLCs are in same cabinet). There I would rather err on the side of safety and use a proper CAT III rated meter (and gear) if I am working on it live. It is not that difficult to have a brain fart and stick a probe in the wrong place or have a transient from a motor turning on or off nearby come down the mains cable while I am checking whether the PLC has power.

[joeqsmith]

In general, I would not use this particular on anything sitting on the factory floor.   

So you don't feel that just because the equipment is in a large industrial environment and runs on 3P, that it is CAT III in all cases.    I was guessing the inverter that drives the head are in a separate enclosure as well and it's output is isolated from the mains with SP going to the head.    I've never worked with one.   

http://przyrbwn.icm.edu.pl/APP/PDF/124/a124z3p20.pdf

 

[janoc]

In general, I would not use this particular on anything sitting on the factory floor.   

So you don't feel that just because the equipment is in a large industrial environment and runs on 3P, that it is CAT III in all cases.    I was guessing the inverter that drives the head are in a separate enclosure as well and it's output is isolated from the mains with SP going to the head.    I've never worked with one.   

http://przyrbwn.icm.edu.pl/APP/PDF/124/a124z3p20.pdf

 

Well, three phase fixed equipment (e.g. elevator motors) or industrial equipment is considered CAT III by default. CAT II is only single phase and usually something plugged into an outlet, not a fixed install. I wouldn't say that everything on a factory floor is always CAT III (maybe some real world industrial sparky can shed some light on this?) but if the gear is on a fixed mains connection, I would assume the worst.

I haven't seen these ultrasonic welders before neither, but that schematics showing the driver switches 400V DC on the primary side at fairly decent currents is enough for me to have a healthy respect for something like that.

[joeqsmith]

Well, three phase fixed equipment (e.g. elevator motors) or industrial equipment is considered CAT III by default. CAT II is only single phase and usually something plugged into an outlet, not a fixed install. I wouldn't say that everything on a factory floor is always CAT III (maybe some real world industrial sparky can shed some light on this?) but if the gear is on a fixed mains connection, I would assume the worst.

I haven't seen these ultrasonic welders before neither, but that schematics showing the driver switches 400V DC on the primary side at fairly decent currents is enough for me to have a healthy respect for something like that.

I've seen a fair amount of 1P equipment hard wired as well.    I wouldn't go poking in that inverter with this meter still output is only 500V RMS max in this example and is isolated.  I'm surprised it damaged the UT61E. 

[janoc]

I wouldn't go poking in that inverter with this meter still output is only 500V RMS max in this example and is isolated.  I'm surprised it damaged the UT61E.

It is a resonant converter - if the load is not present/damaged, there could be high voltages present. And he measured essentially across the output transformer, so whether or not it is isolated doesn't play a role.

[stj]

why does every damned post about a UNI-T get hijacked by the people obsessed with CAT ratings who dont even understand that they are to protect the user and not the meter!!!!

example,
the meter is rated for max 600v, and CATx 1000v
if you put 1000v into it and it dies quietly without bursting open in your hand then where's the problem???

[janoc]

why does every damned post about a UNI-T get hijacked by the people obsessed with CAT ratings who dont even understand that they are to protect the user and not the meter!!!!

example,
the meter is rated for max 600v, and CATx 1000v
if you put 1000v into it and it dies quietly without bursting open in your hand then where's the problem???

The problem is that that 600V rating on that meter is absolute BS and that meter shouldn't have been anywhere near that machine in the first place.

The second problem is that if that meter's ratings weren't fake, it likely wouldn't have broken neither because the test voltages during the CAT testing are about in that same ballpark. If the meter has arced through, like shown in the picture posted by the OP, during the CAT testing,it would have likely been a test failure too (arcing is a reason for a test failure, as is insulation breakdown, even if the meter doesn't blow up or still works). You obviously didn't bother to read the entire thread since you have missed that part.

But thanks for randomly jumping in, not reading but feeling the need to educate us about not understanding what the ratings are for! 

[stj]

i did read the thread, and i know you have absolutly no idea what voltage or waveform hit the meter.

[Fungus]

why does every damned post about a UNI-T get hijacked by the people obsessed with CAT ratings who dont even understand that they are to protect the user and not the meter!!!!

example,
the meter is rated for max 600v, and CATx 1000v
if you put 1000v into it and it dies quietly without bursting open in your hand then where's the problem???

Maybe you watch the thread where they leap around as the copper inside vaporizes and turns to gas (ie. "explosion") at voltages/energies well within the CAT levels.

[shteii01]

Because it has 250V glass fuses?

why does every damned post about a UNI-T get hijacked by the people obsessed with CAT ratings who dont even understand that they are to protect the user and not the meter!!!!

[Fungus]

Because it has 250V glass fuses?

Because they have a lot of blank spaces on the PCB where the safety components are supposed to be?

(and as a result: Because they die if you look at them the wrong way?)

But hey, they say "22000" on the front so that makes them a good meter, right?

[joeqsmith]

I wouldn't go poking in that inverter with this meter still output is only 500V RMS max in this example and is isolated.  I'm surprised it damaged the UT61E.

It is a resonant converter - if the load is not present/damaged, there could be high voltages present. And he measured essentially across the output transformer, so whether or not it is isolated doesn't play a role.

So you don't feel the output transformer will limit the power available to the meter?    To be clear,  I am still trying to understand your Darwin comment and if you feel that there was a high risk that an arc flash could happen looking across the head or if you just feel there was enough energy available at head that could have cause the meter to explode and kill the user?     

Also, when you mention high voltages could be present what are you thinking?  10s of KV?  Sub KV?   Again, I test all the meters to just under 1KV, which included a few of the 61's.   But we also know that to get the BW on the 61E, the way the circuit is designed, fast edge transients will pass right on through.   I demonstrated this.  This is why again that I brought up my piezo tests as the head is a piezo.  The edge rates for ESD are sub ns.   It's also why I mention the EMC vs the safety standards.  There may not be a lot of energy but it's more than enough to damage many UNI-Ts I have looked at.    Their circuit board has very little damage from their picture.  What ever waveform damaged it, there was not a lot of energy.   Had the meter been a GS certified version of the 61E, I have my doubts it would have survived as I don't believe they are certified for EMC.

[stj]

Because it has 250V glass fuses?

why does every damned post about a UNI-T get hijacked by the people obsessed with CAT ratings who dont even understand that they are to protect the user and not the meter!!!!

fuses are for current, not voltage range.

[Damianos]

This instrument is specified for voltage measurements up to 10kHz and it used on an ultrasonic device!
What does anyone expect from any instrument when used outside of its specifications?
In the manuals of more expensive instruments there is more information about this, such as a derating factor or also a diagram showing the maximum voltage relative to frequency.
Even if it had been used on a CAT-I device, the result would be similar ...

[stj]

love your Avatar!! 

[janoc]

I wouldn't go poking in that inverter with this meter still output is only 500V RMS max in this example and is isolated.  I'm surprised it damaged the UT61E.

It is a resonant converter - if the load is not present/damaged, there could be high voltages present. And he measured essentially across the output transformer, so whether or not it is isolated doesn't play a role.

So you don't feel the output transformer will limit the power available to the meter?    To be clear,  I am still trying to understand your Darwin comment and if you feel that there was a high risk that an arc flash could happen looking across the head or if you just feel there was enough energy available at head that could have cause the meter to explode and kill the user?     

AFAIK, that hardware was something in the 500W ballpark. So even if the transformer does limit the current, there will still be plenty of energy around for one mighty bang. But my primary concern was not so much the ultrasonic head itself but that the OP was poking around a three phase industrial installation with this meter. A high energy environment with a good possibility of high voltage transients.

Also, when you mention high voltages could be present what are you thinking?  10s of KV?  Sub KV?   Again, I test all the meters to just under 1KV, which included a few of the 61's.   But we also know that to get the BW on the 61E, the way the circuit is designed, fast edge transients will pass right on through.   I demonstrated this.  This is why again that I brought up my piezo tests as the head is a piezo.  The edge rates for ESD are sub ns.   It's also why I mention the EMC vs the safety standards.  There may not be a lot of energy but it's more than enough to damage many UNI-Ts I have looked at.    Their circuit board has very little damage from their picture.  What ever waveform damaged it, there was not a lot of energy.   Had the meter been a GS certified version of the 61E, I have my doubts it would have survived as I don't believe they are certified for EMC.

I believe I have replied to this few times already. The CAT testing requires the meter to withstand 4-6kV (depending on which CAT rating is the test for), without arcing or insulation breakdown (i.e. there must not be any current increase beyond the initial capacitance charge up). If the meter has died because of short ESD pulse, as you are suspecting, then don't you think it would have died also when the same voltage has been applied long term during the CAT tests? (and thus failing the test because of arcing/insulation breakdown). I don't know how steep the test waveform edges are, but the only protection device where this could make a difference are the input clamping diodes - if the edge is short enough that the diode doesn't conduct in time. On the other hand, how much energy could a pulse that short that a diode doesn't open deliver? Enough to blacken the range switch? I somehow doubt that - we would see tons of electronics failing due to ESD left and right in that case (lot of electronics has only the clamping diodes as protection).

Also the fact that the horn is a piezzo is actually a red herring - he wasn't measuring the output of a piezoelectric generator (like your lighter!) but an output of some 30-40kHz driver. Those aren't going to have super fast edges. If for nothing else then for EMI reasons.

Of course, this discussion is pretty academical because the original meter obviously hasn't been CAT tested. And the German version that has been doesn't meet those ratings even with the extra protection devices installed.

[janoc]

This instrument is specified for voltage measurements up to 10kHz and it used on an ultrasonic device!
What does anyone expect from any instrument when used outside of its specifications?
In the manuals of more expensive instruments there is more information about this, such as a derating factor or also a diagram showing the maximum voltage relative to frequency.
Even if it had been used on a CAT-I device, the result would be similar ...

Yep, good point too. I am not quite sure what the OP has been attempting to measure there.

[joeqsmith]

AFAIK, that hardware was something in the 500W ballpark. So even if the transformer does limit the current, there will still be plenty of energy around for one mighty bang. But my primary concern was not so much the ultrasonic head itself but that the OP was poking around a three phase industrial installation with this meter. A high energy environment with a good possibility of high voltage transients.

OK, so you feel a 0.5KW 500V AC RMS supply is enough to cause an arc flash, explode the meter and kill the operator.   I really have no idea what it would take myself to have one come apart. 

Also, when you mention high voltages could be present what are you thinking?  10s of KV?  Sub KV?   Again, I test all the meters to just under 1KV, which included a few of the 61's.   But we also know that to get the BW on the 61E, the way the circuit is designed, fast edge transients will pass right on through.   I demonstrated this.  This is why again that I brought up my piezo tests as the head is a piezo.  The edge rates for ESD are sub ns.   It's also why I mention the EMC vs the safety standards.  There may not be a lot of energy but it's more than enough to damage many UNI-Ts I have looked at.    Their circuit board has very little damage from their picture.  What ever waveform damaged it, there was not a lot of energy.   Had the meter been a GS certified version of the 61E, I have my doubts it would have survived as I don't believe they are certified for EMC.

I believe I have replied to this few times already. The CAT testing requires the meter to withstand 4-6kV (depending on which CAT rating is the test for), without arcing or insulation breakdown (i.e. there must not be any current increase beyond the initial capacitance charge up). If the meter has died because of short ESD pulse, as you are suspecting, then don't you think it would have died also when the same voltage has been applied long term during the CAT tests? (and thus failing the test because of arcing/insulation breakdown).

To be clear, I am suspecting a fast edge but not a static discharge but I don't know.   Sure the energy, waveshape, impedance will all come into play.  If you are asking if I think a device could survive ESD and not surge, sure.  Also, I believe the opposite is true.  There is a reason both are tested.   They are also not an end all.  Meaning if you pass every test the IEC standards call out, its not certain the product would survive in the field.

I don't know how steep the test waveform edges are, but the only protection device where this could make a difference are the input clamping diodes - if the edge is short enough that the diode doesn't conduct in time. On the other hand, how much energy could a pulse that short that a diode doesn't open deliver? Enough to blacken the range switch? I somehow doubt that - we would see tons of electronics failing due to ESD left and right in that case (lot of electronics has only the clamping diodes as protection).

Also the fact that the horn is a piezzo is actually a red herring - he wasn't measuring the output of a piezoelectric generator (like your lighter!) but an output of some 30-40kHz driver. Those aren't going to have super fast edges. If for nothing else then for EMI reasons.

Of course, this discussion is pretty academical because the original meter obviously hasn't been CAT tested. And the German version that has been doesn't meet those ratings even with the extra protection devices installed.

Surge is 1.2us rise.  Pretty slow compared to burst.  I am not sure what all the handheld meters needs to do to pass.   It's all on the safety side of things anyway.   I think you are correct that normally you would not be looking at the output of a piezo generator and it is fairly slow.     However, they were working on the unit because their was a problem.  I don't know on a welder like this if the head is active and you have the meter across it, if the circuit to the head opens whats happens.   Would you see a low energy high voltage fast edge event similar to ESD?

I missed your last comment.  The GS certified 61E does not meet what ratings? 

(added more detail)

[SeanB]

Ultrasonic transducers are almost invariably a tuned LC parallel circuit with the driver pumping it to maintain it, the circulating currents are pretty high, along with the voltages. Voltage depends on the loading, and if the transducer is not too healthy, or if there is no loading then the voltages rise up to really high levels. That the edges are slow is not too much of a concern, even 100pF of capacitor will pass appreciable current at 40kHz if the protection is designed to survive a single cycle of voltage, and dissipate the energy over a 10s period between pulses,
and you slam the same energy in there 400 thousand times, something will melt  or simply turn to vapour.

Ultrasonic transducers in industry are generally only a capacitor with high losses, only in echo location do you get the transducer with integrated transformer, as the cables are long, and it is a lot easier to drive a low voltage high current with a transformer to convert impedance at the far end, than to have an ultra low capacitance cable that will be routable easily and survive ultra high voltages as well cheaply. Ultrasonic cleaners to tend to turn transducers into smoke and shrapnel quite easily, I have a few samples of that in cheap cleaners, but the drivers often survive with only blown diode bridges, dead switching transistors and a blown mains fuse. Transducer is just charcoal.

[janoc]

AFAIK, that hardware was something in the 500W ballpark. So even if the transformer does limit the current, there will still be plenty of energy around for one mighty bang. But my primary concern was not so much the ultrasonic head itself but that the OP was poking around a three phase industrial installation with this meter. A high energy environment with a good possibility of high voltage transients.

OK, so you feel a 0.5KW 500V AC RMS supply is enough to cause an arc flash, explode the meter and kill the operator.   I really have no idea what it would take myself to have one come apart. 

That is not what I have said. I have said that the horn supply is in a 500W ballpark. The voltage on the secondary could be a lot higher than a 500V if the load is not connected/broken. Whether or not this will make the meter explode, cause an arc flash and what not I don't know. Only a lab would be able to answer that. However, we could get some clue from the fact that that meter has been able to pass the only much less strict testing - and with improved input protection, at that. So something obviously did blow up during the German tests.

What I know is that that meter isn't safe to use in such environment. Both because the input protection is not sufficient (even 500V shorting through a poorly built meter can hurt you!) and because the installation is such that high voltage transients are possible there (the machine being a part of fixed 3 phase industrial installation).

To be clear, I am suspecting a fast edge but not a static discharge but I don't know.   Sure the energy, waveshape, impedance will all come into play.  If you are asking if I think a device could survive ESD and not surge, sure.  Also, I believe the opposite is true.  There is a reason both are tested.   They are also not an end all.  Meaning if you pass every test the IEC standards call out, its not certain the product would survive in the field.

OK.

Surge is 1.2us rise.  Pretty slow compared to burst.  I am not sure what all the handheld meters needs to do to pass.   It's all on the safety side of things anyway.   I think you are correct that normally you would not be looking at the output of a piezo generator and it is fairly slow.     However, they were working on the unit because their was a problem.  I don't know on a welder like this if the head is active and you have the meter across it, if the circuit to the head opens whats happens.   Would you see a low energy high voltage fast edge event similar to ESD?

I think that if the circuit suddenly opens (the load gets disconnected), the voltage will rise relatively slowly, IMO, being limited by the parasitics of the transformer.

I missed your last comment.  The GS certified 61E does not meet what ratings? 

(added more detail)

The GS certfied one (I assume that is the version Batronix is selling) is rated only CAT II 600V and CAT III 300V, as opposed to the original Chinese one claiming CAT III 1000V and CAT IV 600V (which the OP seems to have, given the lack of isolation slots in the board photo he posted). So the Batronix meter has been tested (or rather - passed) tests only to lower voltages.

[joeqsmith]

That is not what I have said. I have said that the horn supply is in a 500W ballpark. The voltage on the secondary could be a lot higher than a 500V if the load is not connected/broken. Whether or not this will make the meter explode, cause an arc flash and what not I don't know. Only a lab would be able to answer that. However, we could get some clue from the fact that that meter has been able to pass the only much less strict testing - and with improved input protection, at that. So something obviously did blow up during the German tests.

What I know is that that meter isn't safe to use in such environment. Both because the input protection is not sufficient (even 500V shorting through a poorly built meter can hurt you!) and because the installation is such that high voltage transients are possible there (the machine being a part of fixed 3 phase industrial installation).

Because you initially brought of the safety concerns and that this was a Darwin move and I have asked you several times if you really felt the OP was at risk if the meter exploding and killing them while measuring the head, I assumed that you were finally answering this.   So it sounds like you really don't know what it would take to explode the meter and kill the user.   That said, again, why does it get the Darwin award? 

Surge is 1.2us rise.  Pretty slow compared to burst.  I am not sure what all the handheld meters needs to do to pass.   It's all on the safety side of things anyway.   I think you are correct that normally you would not be looking at the output of a piezo generator and it is fairly slow.     However, they were working on the unit because their was a problem.  I don't know on a welder like this if the head is active and you have the meter across it, if the circuit to the head opens whats happens.   Would you see a low energy high voltage fast edge event similar to ESD?

I think that if the circuit suddenly opens (the load gets disconnected), the voltage will rise relatively slowly, IMO, being limited by the parasitics of the transformer.

As stated, the circuit to the head opens and the meter stays across the head.  The head is already excited.   

The GS certfied one (I assume that is the version Batronix is selling) is rated only CAT II 600V and CAT III 300V, as opposed to the original Chinese one claiming CAT III 1000V and CAT IV 600V. So the Batronix meter has been tested (or rather - passed) tests only to lower voltages.

OK, sounded like the claim was the GS mark was worthless.  This makes more sense.   I've lost track of what your original reason for posting was.   

[janoc]

Because you initially brought of the safety concerns and that this was a Darwin move and I have asked you several times if you really felt the OP was at risk if the meter exploding and killing them while measuring the head, I assumed that you were finally answering this.   So it sounds like you really don't know what it would take to explode the meter and kill the user.   That said, again, why does it get the Darwin award? 

I feel we are running in circles with this. Isn't taking a known-unsafe meter with fake safety ratings to an industrial three phase installation with a high voltage present enough for you? I have never claimed that the meter will explode or anything of the sort.

What certainly could explode the meter and kill the user is if the there is a mains transient while that meter is being used on that mains powered machine. That Uni-T meter certainly isn't built to withstand something like that. 

As stated, the circuit to the head opens and the meter stays across the head.  The head is already excited.   

That head behaves as a (poor) capacitor. So all that will happen in such case is that the meter will get exposed to whatever voltage that capacitor was left charged to, perhaps with some dampened ringing for a bit. The driver is more dangerous because if the load disappears, the voltage will shoot up, potentially breaking down insulation, causing arcing and other problems.

OK, sounded like the claim was the GS mark was worthless.  This makes more sense.   I've lost track of what your original reason for posting was.

No no, I have never claimed it was worthless. I was merely pointing out that the GS-tested meter has been tested to a lower standard than what the original meter claimed to fulfill. Work on that type of installation would have required a meter that has been actually certified to that CAT IV rating.

[joeqsmith]

I feel we are running in circles with this. Isn't taking a known-unsafe meter with fake safety ratings to an industrial three phase installation with a high voltage present enough for you? I have never claimed that the meter will explode or anything of the sort.

What certainly could explode the meter and kill the user is if the there is a mains transient while that meter is being used on that mains powered machine. That Uni-T meter certainly isn't built to withstand something like that. 

I'm just along for the ride keeping you company.  I already stated I would never take an uncertified meter into this environment and I've certainly voiced my opinion on UNI-T in general. 

As stated, the circuit to the head opens and the meter stays across the head.  The head is already excited.   

That head behaves as a (poor) capacitor. So all that will happen in such case is that the meter will get exposed to whatever voltage that capacitor was left charged to, perhaps with some dampened ringing for a bit. The driver is more dangerous because if the load disappears, the voltage will shoot up, potentially breaking down insulation, causing arcing and other problems.

I would have thought if you monitored the voltage across the head and stuck the output end, you would see some sort of transient.   

OK, sounded like the claim was the GS mark was worthless.  This makes more sense.   I've lost track of what your original reason for posting was.

No no, I have never claimed it was worthless. I was merely pointing out that the GS-tested meter has been tested to a lower standard than what the original meter claimed to fulfill. Work on that type of installation would have required a meter that has been actually certified to that CAT IV rating.

   Why do you feel CAT IV would be required to look across the head?  Or are you suggesting in general you feel a CAT IV meter is required to for a CAT III environment?    Or you feel this is a CAT IV environment?

[joeqsmith]

Also, I wonder how you feel about the Wiki page:

https://en.wikipedia.org/wiki/Measurement_category

Accurate or needs updates?

[janoc]

   Why do you feel CAT IV would be required to look across the head?  Or are you suggesting in general you feel a CAT IV meter is required to for a CAT III environment?    Or you feel this is a CAT IV environment?

No, I don't.

The machine is most likely CAT III and the original meter claimed CAT III/CAT IV compliance, that's why I have mentioned that. Having CAT III/IV rating would be good to have in case there is a mains transient - it is a fixed installation that is being measured live. Nothing to do with the head per se, apart from maybe better chances of withstanding the high voltages there because of a better input protection a CAT III/IV certified meter will have.

EDIT: Doh, just re-read my original comment saying it would have required CAT IV meter - I see why you are asking now. That's wrong, I meant to write CAT III but the meter was claiming CAT III/CAT IV compliance so I had that in my head. Sorry for the confusion.

[janoc]

Also, I wonder how you feel about the Wiki page:

https://en.wikipedia.org/wiki/Measurement_category

Accurate or needs updates?

Seems to be the same as what is in that Fluke document I have linked earlier, which is taken from the IEC standard. But I think what is more relevant are the national norms that are based on this general categorization.