Author Topic: UNI-T UT61E First Problem...  (Read 15954 times)

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Offline hggTopic starter

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UNI-T UT61E First Problem...
« on: December 28, 2013, 01:36:43 pm »
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.
 

Offline Monkeh

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Re: UNI-T UT61E First Problem...
« Reply #1 on: December 28, 2013, 01:39:55 pm »
The data mode is always on. You were never able to turn it off.

Shorting current sources through your meter is a bad idea.
 
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Offline hggTopic starter

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Re: UNI-T UT61E First Problem...
« Reply #2 on: December 28, 2013, 01:47:23 pm »
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?
 

Offline sync

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Re: UNI-T UT61E First Problem...
« Reply #3 on: December 28, 2013, 01:50:28 pm »
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.
 

Offline hggTopic starter

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Re: UNI-T UT61E First Problem...
« Reply #4 on: December 28, 2013, 01:59:21 pm »
You are right, I am not thinking today...   :palm:
 

Offline seanspotatobusiness

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Re: UNI-T UT61E First Problem...
« Reply #5 on: December 02, 2016, 08:05:48 pm »
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?
 

Offline janoc

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Re: UNI-T UT61E First Problem...
« Reply #6 on: December 02, 2016, 09:40:43 pm »
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.

 

Offline joeqsmith

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Re: UNI-T UT61E First Problem...
« Reply #7 on: December 03, 2016, 04:52:15 pm »
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. 


 
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Offline sergiusora

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Re: UNI-T UT61E First Problem...
« Reply #8 on: December 15, 2017, 06:03:08 pm »
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.
 

Offline joeqsmith

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Re: UNI-T UT61E First Problem...
« Reply #9 on: December 15, 2017, 06:57:59 pm »
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?

Offline sergiusora

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Re: UNI-T UT61E First Problem...
« Reply #10 on: December 16, 2017, 12:36:51 pm »
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 .
 

Offline joeqsmith

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Re: UNI-T UT61E First Problem...
« Reply #11 on: December 16, 2017, 04:06:19 pm »
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. 

Offline sergiusora

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Re: UNI-T UT61E First Problem...
« Reply #12 on: December 16, 2017, 05:23:16 pm »
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.
 

Offline Fungus

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Re: UNI-T UT61E First Problem...
« Reply #13 on: December 16, 2017, 05:32:30 pm »
If you're going to buy a new meter it might be worth considering something a bit more robust, eg. A Fluke 15B+/17B+.

 

Offline janoc

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Re: UNI-T UT61E First Problem...
« Reply #14 on: December 16, 2017, 07:17:38 pm »
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.
 

Offline joeqsmith

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Re: UNI-T UT61E First Problem...
« Reply #15 on: December 16, 2017, 07:58:39 pm »
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.

Offline janoc

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Re: UNI-T UT61E First Problem...
« Reply #16 on: December 16, 2017, 11:12:56 pm »
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 ...

« Last Edit: December 16, 2017, 11:26:52 pm by janoc »
 
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Offline joeqsmith

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Re: UNI-T UT61E First Problem...
« Reply #17 on: December 16, 2017, 11:57:27 pm »
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.

Offline janoc

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Re: UNI-T UT61E First Problem...
« Reply #18 on: December 17, 2017, 03:33:18 pm »
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.

 

Offline joeqsmith

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Re: UNI-T UT61E First Problem...
« Reply #19 on: December 17, 2017, 04:20:06 pm »
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. 

Offline janoc

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Re: UNI-T UT61E First Problem...
« Reply #20 on: December 17, 2017, 04:53:37 pm »
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 ...


« Last Edit: December 17, 2017, 05:06:24 pm by janoc »
 

Offline Fungus

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Re: UNI-T UT61E First Problem...
« Reply #21 on: December 17, 2017, 05:09:15 pm »
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.  :-//

 

Offline SeanB

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Re: UNI-T UT61E First Problem...
« Reply #22 on: December 17, 2017, 08:07:13 pm »
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.
 
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Offline janoc

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Re: UNI-T UT61E First Problem...
« Reply #23 on: December 17, 2017, 09:44:53 pm »
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.
 

Offline joeqsmith

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Re: UNI-T UT61E First Problem...
« Reply #24 on: December 17, 2017, 10:10:03 pm »
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..  :palm:


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