UNI-T UT61E First Problem...

[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.