DMM Questions: Protection, Hz Measurement, Shunt?

[joeqsmith]

So, what Flooby said?

Yes.

I thought you had watched the eevblog video on dmm input protection?
All this had been covered in that video.

Multiple techniques  are needed in order to fully protect a dmm:
Over voltage
Surge suppression
Over current
Energy dissipation
If you skip some of them, then better make sure the dmm will fail in a safe way for the user.

It's a beginner area and I wouldn't expect the OP to have a formal education in EE or to be able to watch a technical video and understand the information being presented.   

Actually, much of what is being asked, I would need to ask a few safety experts who specialize in handheld meters to answer with any level of confidence.     

When I run meters that use the 5mm PTC with no series resistance, typically the PTCs fail (see attached). Once they short (arc over), there is nothing but my generator's source impedance (2 ohms),  traces, leads and the function switch to limit the current.  We basically end up with a fair bit of current going to the clamp.  20 Joules isn't much but for these small devices, they typically come apart.  The next in the chain is the IC  which will commonly end up with a cracked case.

The small clamps are normally located downstream from the function switch.  Sometimes I get lucky and some unintended area with breakdown (arc) and absorb enough to save the meter from the recycle bin.    The UNI-T UT90A has been a very good example of this.   You can see the last repairs in the attached pictures.  I would not suggest the UT90 survived my tests, nor would I suggest it is an electrically robust meter.

[DW1961]

So, what Flooby said?

Yes.

I thought you had watched the eevblog video on dmm input protection?
All this had been covered in that video.

Multiple techniques  are needed in order to fully protect a dmm:
Over voltage
Surge suppression
Over current
Energy dissipation
If you skip some of them, then better make sure the dmm will fail in a safe way for the user.

I did watch it but I was specifically addressing how MOVs assist PTCs in that reply becasue I  do not understanding how a transistor could or could not do that.

I wish he would send me the schematic on it.

I did asks how a tiny transistor could protect against voltage surge and over voltage, and he replied it was a technical discussion that was too involved to go into, or something like that. You have to really watch for language miscommunications. So, I asked for the schematic.

[DW1961]

So, what Flooby said?

Yes.

I thought you had watched the eevblog video on dmm input protection?
All this had been covered in that video.

Multiple techniques  are needed in order to fully protect a dmm:
Over voltage
Surge suppression
Over current
Energy dissipation
If you skip some of them, then better make sure the dmm will fail in a safe way for the user.

It's a beginner area and I wouldn't expect the OP to have a formal education in EE or to be able to watch a technical video and understand the information being presented.   

Actually, much of what is being asked, I would need to ask a few safety experts who specialize in handheld meters to answer with any level of confidence.     

When I run meters that use the 5mm PTC with no series resistance, typically the PTCs fail (see attached). Once they short (arc over), there is nothing but my generator's source impedance (2 ohms),  traces, leads and the function switch to limit the current.  We basically end up with a fair bit of current going to the clamp.  20 Joules isn't much but for these small devices, they typically come apart.  The next in the chain is the IC  which will commonly end up with a cracked case.

The small clamps are normally located downstream from the function switch.  Sometimes I get lucky and some unintended area with breakdown (arc) and absorb enough to save the meter from the recycle bin.    The UNI-T UT90A has been a very good example of this.   You can see the last repairs in the attached pictures.  I would not suggest the UT90 survived my tests, nor would I suggest it is an electrically robust meter.

Hey Joe, thanks.

I did understand much of it in a simple way, such as how MOVs assist in letting PTCs catch up to regulate voltage, since the PTC reacts to heat much more slowly than an MOV can. I can follow that. Dave was really clear about it too. How the diode bridge worked was really interesting also, but since I don't understand exactly what and how diodes do and work, I'm going to have difficulty putting it all together in one cohesive idea, such as how much energy can diodes redirect and when you need to use something else. I'm learning.

[bdunham7]

Sometimes I get lucky and some unintended area with breakdown (arc) and absorb enough to save the meter from the recycle bin.   

How would that work out in a fully energized CAT test?

[DW1961]

The diode-connected transistors clamp the overload hard at first, then the PTC heats up and the fault current backs off.

That is what I wish my motherboard had on its LED circuits. That way if an LED strip's resistors let go or there is a short in the strip, it doesn't melt the RGB Fets. (Like what happened to me, and I still haven't gotten my main rig back up yet )

I've almost finished rebuilding my LED strips. I've tested each connection after soldering and have no shorts that I can detect using continuity. I'm going to do a current test tonight and let them run 24 hours on full blast to make sure they don't short or whatever they do when something isn't right. I figure if I can leave them on 24 hours WFO without any current problems,  they're good to go back into my computer and I can wrap it up (Given the motherboard replacement they sent me is not defective itself.). Scared to let the magic smoke out again.

[Gyro]

So, what Flooby said?

Yes.

I thought you had watched the eevblog video on dmm input protection?
All this had been covered in that video.

Multiple techniques  are needed in order to fully protect a dmm:
Over voltage
Surge suppression
Over current
Energy dissipation
If you skip some of them, then better make sure the dmm will fail in a safe way for the user.

I did watch it but I was specifically addressing how MOVs assist PTCs in that reply becasue I  do not understanding how a transistor could or could not do that.

I wish he would send me the schematic on it.

I did asks how a tiny transistor could protect against voltage surge and over voltage, and he replied it was a technical discussion that was too involved to go into, or something like that. You have to really watch for language miscommunications. So, I asked for the schematic.

I think you have your indication from the above discussions, to a good level of confidence, that the manufacturer has used a little bit more silk-screen ink on the front panel than he was entitled to. He is, after all, trying to compete with other low cost manufacturers who are doing exactly the same thing. It's just an option for them, if the customer (distributor) wants a 'IV' on the front then they will happily print one at no extra charge. If an internal inspection doesn't show that it is not a Class IV 600V product, then the selling price should.

I sometimes enjoy winding up telephone scammers for long periods (other times I can't be bothered). Feel free to keep torturing the seller (who isn't the manufacturer, probably not even the distributor) for as long as gives you satisfaction. You might get the schematic, which might be of minor interest, although it is pretty clear what is and isn't on the board (The PCB layout might be more interesting so that you can see both sides without dismantling the switch), but I don't think you can expect him to come up with some miracle vindication at this point.

There's no particular harm in making life awkward for him though, just so long as you don't have expectations of a meaningful answer.

[MosherIV]

I did watch it but I was specifically addressing how MOVs assist PTCs in that reply becasue I  do not understanding how a transistor could or could not do that.

I wish he would send me the schematic on it.

I did asks how a tiny transistor could protect against voltage surge and over voltage, and he replied it was a technical discussion that was too involved to go into, or something like that. You have to really watch for language miscommunications. So, I asked for the schematic.

The diode/transistor clamp is usually used close to the meters ADC inputs to protect them from over voltage. This will be after resistor divider network to drop the voltage to a range the ADC can handle.  The over voktage clamp are not able to cope with large currents. When they turn on, they will just short out the over voltage, in shorting they must be capable of passing the current. That is what some of the other were saying, that under some circumstances, they doubt the clamping devices can handle the current.

Typically, MOVs are used before the resistor divider networks. They will short out the over voltage and allow the PTCs time to increase resistance, thereby reduce any current.

As I said these are 2 different mechamsims to protect the dmm. They should not be confused with each other. Relying on just one of them to protect the dmm will not work under all circumstances.

[joeqsmith]

Sometimes I get lucky and some unintended area with breakdown (arc) and absorb enough to save the meter from the recycle bin.   

How would that work out in a fully energized CAT test?

Hard to say but I doubt burst and surge would do near the damage as an arcflash test would.   

I built what I refer to as a half cycle line simulator.  It can put out a low voltage fairly high current wave.    It is used in conjunction with the high voltage generator.   Basically the high voltage short duration transient rides on top of the low voltage high energy wave.   If a meter, like the UT90A were to break down from the high voltage transient, rather than the 20 Joules, we can feed in roughly 600 J to sustain the arc.  The half cycle line simulator still uses a 2 ohm source and the energy it produces is normally absorbed by the high voltage generators output network.  600J is no where near what even a combo generator would typically provide.   It does command some respect as coming in contact with the output could prove lethal.   Again, nothing new and has been explained many times in various videos.   

If you watch this video, starting at the link you can see where the UT90As damage came from.
https://youtu.be/aRuI_q_K5RY?t=351

A toy compared with an arcflash, or even a real surge test.   

[joeqsmith]

Attempting to determine the root cause of failure for an old Fluke 87V.   Video goes over the front end and there is a model of it that I transient test.   Should give some visual idea of what is happening with the various stages of clamps. 

[E-Design]

So, what Flooby said?

Yes.

I thought you had watched the eevblog video on dmm input protection?
All this had been covered in that video.

Multiple techniques  are needed in order to fully protect a dmm:
Over voltage
Surge suppression
Over current
Energy dissipation
If you skip some of them, then better make sure the dmm will fail in a safe way for the user.

I did watch it but I was specifically addressing how MOVs assist PTCs in that reply becasue I  do not understanding how a transistor could or could not do that.

I wish he would send me the schematic on it.

I did asks how a tiny transistor could protect against voltage surge and over voltage, and he replied it was a technical discussion that was too involved to go into, or something like that. You have to really watch for language miscommunications. So, I asked for the schematic.

I think you have your indication from the above discussions, to a good level of confidence, that the manufacturer has used a little bit more silk-screen ink on the front panel than he was entitled to. He is, after all, trying to compete with other low cost manufacturers who are doing exactly the same thing. It's just an option for them, if the customer (distributor) wants a 'IV' on the front then they will happily print one at no extra charge. If an internal inspection doesn't show that it is not a Class IV 600V product, then the selling price should.

I sometimes enjoy winding up telephone scammers for long periods (other times I can't be bothered). Feel free to keep torturing the seller (who isn't the manufacturer, probably not even the distributor) for as long as gives you satisfaction. You might get the schematic, which might be of minor interest, although it is pretty clear what is and isn't on the board (The PCB layout might be more interesting so that you can see both sides without dismantling the switch), but I don't think you can expect him to come up with some miracle vindication at this point.

There's no particular harm in making life awkward for him though, just so long as you don't have expectations of a meaningful answer.

While the discussion and topics in this thread are all very enlightening and interesting for all of us, I predict that pestering the seller wont lead to anything at all. At some point, they will tire of the inquiries and just go away.
Also, if the end goal is to expose these cheap meters as being untrustworthy, thats already been established for  a long time and more so even now to the few people in the know.
If the goal is to affect change in the marketplace offerings against Chinese companies because they are "Illegal" - Its a waste of time.

What is the OPs time worth to him to carry on with sellers. And all the talk of illegal products and rating... , Pshhh nobody on Amazon is going to react to that without the Lawyers involved. And exactly how many lawyers are here in this thread rallying behind the OP ? Joe Blow can make claims to Amazon all day long. Could be that as soon as a Lawyer writes the the Shenzhen based company, they produce the documentation showing compliance. They dont have to give anybody anything. As I understand it, its also mission impossible trying to litigate against Chinese companies anyhow - that is if you can even find out who it is. Unfortunately, it will likely require somebody getting injured for a Lawyer to get involved with motivation.

Not trying to stifle the efforts, but I think that if there is an expectation that this brings change,  it is incorrect. Give them bad ratings, learn something about CAT ratings and cheapo meter design and move on?

[DW1961]

So, what Flooby said?

Yes.

I thought you had watched the eevblog video on dmm input protection?
All this had been covered in that video.

Multiple techniques  are needed in order to fully protect a dmm:
Over voltage
Surge suppression
Over current
Energy dissipation
If you skip some of them, then better make sure the dmm will fail in a safe way for the user.

I did watch it but I was specifically addressing how MOVs assist PTCs in that reply becasue I  do not understanding how a transistor could or could not do that.

I wish he would send me the schematic on it.

I did asks how a tiny transistor could protect against voltage surge and over voltage, and he replied it was a technical discussion that was too involved to go into, or something like that. You have to really watch for language miscommunications. So, I asked for the schematic.

I think you have your indication from the above discussions, to a good level of confidence, that the manufacturer has used a little bit more silk-screen ink on the front panel than he was entitled to. He is, after all, trying to compete with other low cost manufacturers who are doing exactly the same thing. It's just an option for them, if the customer (distributor) wants a 'IV' on the front then they will happily print one at no extra charge. If an internal inspection doesn't show that it is not a Class IV 600V product, then the selling price should.

I sometimes enjoy winding up telephone scammers for long periods (other times I can't be bothered). Feel free to keep torturing the seller (who isn't the manufacturer, probably not even the distributor) for as long as gives you satisfaction. You might get the schematic, which might be of minor interest, although it is pretty clear what is and isn't on the board (The PCB layout might be more interesting so that you can see both sides without dismantling the switch), but I don't think you can expect him to come up with some miracle vindication at this point.

There's no particular harm in making life awkward for him though, just so long as you don't have expectations of a meaningful answer.

I'm not trying to tie him up. I'm just wanting to understand if the meter can withstand voltage surge and arc flash for the CAT rating without harming the user. The problem is that in order to get that information, without assuming it, is to find someone with a voltage spike machine and spike it with 8000V while the leads are in the current or other than voltage or hit it with whatever current it is suppose to be able to withstand and see what happens.

 I just submitted the review saying there weren't any MOVs on it and that the resistors and PTCs were small, no guard tracks on the PCB, no case blades, etc. But in honesty I can't say anything else because no one knows how it will fail. I'm not going to give it a bad review on speculation.

I never heard back from him since I asked for schematics, so I'm done with it.

[MosherIV]

I'm just wanting to understand. If the meter can withstand voltage surge and arc flash for the CAT rating without harming the user.

Many forum members have already expressed their view that it is unlikely.

The most practicle way to know is to have the dmm tested by a test laboratory which certify these safety things,  such as UL (underwriters laboratory) - others exist but I do not remember right now.
Quality dmm manufacturers do this for you, you will find that the quality name have the logo of the certifying lab somewhere on the dmm.
These tests are not cheap and that and the engineering effort is reflected in the price.
You get what you pay for!

There are a few exceptions:
https://www.eevblog.com/forum/testgear/heads-up-cheap-multimeter-lidl-uk-(080218)/25/
Around $20 and it has a certified safety logo, some have even checked the lab report.
Safety rating is not great 250V CAT2
The point is that it has been tested by independant lab and verified to protect the user (not the dmm).
The dmm is basically a dt830 in a larger form factor.

BTW even the quality name brand dmm may not survive

Near the end, Dave blows up a classic Fluke 70, it does not survive but the dmm contained the internal explosion (apart from the flying knob  ) FYI these 70 series 1 predate the CAT ratings.

[Gyro]

I think you have your indication from the above discussions, to a good level of confidence, that the manufacturer has used a little bit more silk-screen ink on the front panel than he was entitled to. He is, after all, trying to compete with other low cost manufacturers who are doing exactly the same thing. It's just an option for them, if the customer (distributor) wants a 'IV' on the front then they will happily print one at no extra charge. If an internal inspection doesn't show that it is not a Class IV 600V product, then the selling price should.

I sometimes enjoy winding up telephone scammers for long periods (other times I can't be bothered). Feel free to keep torturing the seller (who isn't the manufacturer, probably not even the distributor) for as long as gives you satisfaction. You might get the schematic, which might be of minor interest, although it is pretty clear what is and isn't on the board (The PCB layout might be more interesting so that you can see both sides without dismantling the switch), but I don't think you can expect him to come up with some miracle vindication at this point.

There's no particular harm in making life awkward for him though, just so long as you don't have expectations of a meaningful answer.

I'm not trying to tie him up. I'm just wanting to understand. If the meter can withstand voltage surge and arc flash for the CAT rating without harming the user. The problem is that in order to get that information, without assuming it, is to find someone with a voltage spike machine and spike it with 8000V while the leads are in the current or other than voltage or hit it with whatever current it is suppose to be able to withstand and see what happens.

 I just submitted the review saying there weren't any MOVs on it and that the resistors and PTCs were small, no guard tracks on the PCB, no case blades, etc. But in honesty I can't say anything else because no one knows how it will fail. I'm not going to give it a bad review on speculation.

I never heard back from him since I asked for schematics, so I'm done with it.

Sure, this thread has turned into a very useful educational one.

I just wanted to be sure that you didn't have greater expectations of what the the seller, Amazon etc. would do. As I said, there is sometimes some satisfaction to be gained from winding up particularly persistent phone scammers and dodgy sellers, but it's unlikely that it will ever get past that individual, it can be fun though.

[joeqsmith]

I'm not trying to tie him up. I'm just wanting to understand. If the meter can withstand voltage surge and arc flash for the CAT rating without harming the user. The problem is that in order to get that information, without assuming it, is to find someone with a voltage spike machine and spike it with 8000V while the leads are in the current or other than voltage or hit it with whatever current it is suppose to be able to withstand and see what happens.

At what level?  The typical internet Wiki level?  From the EE level? The designer?  The safety inspector? The people writing the standards?  The people running the tests?  ...  I would imagine to be an expert in safety for handheld meters, you would make a career out of it.   

The voltage spike machine is a combo generator.  There are both current and voltage waveform requirements.   I am not aware where the surge or burst are applied to the current inputs.   It would seem rather dumb as you would be shorting out the generator, blowing the fuse before the test even starts. 

The most practicle way to know is to have the dmm tested by a test laboratory which certify these safety things,  such as UL (underwriters laboratory) - others exist but I do not remember right now.
....
BTW even the quality name brand dmm may not survive

Near the end, Dave blows up a classic Fluke 70, it does not survive but the dmm contained the internal explosion (apart from the flying knob  ) FYI these 70 series 1 predate the CAT ratings.

Agree, that the only way for a laymen to know is to have them certified. 

I watched that video you linked when it first came out and like my own tests, I don't believe you will find it has anything to do with the safety standards.  I will need to go back and watch it.    So if a meter survived what they were exposing them to or not would have little to do with how they would handle the actual surge or burst tests.   If you believe I am wrong about this, I will watch it again.

[MosherIV]

I watched that video you linked when it first came out and like my own tests, I don't believe you will find it has anything to do with the safety standards.

The video has nothing to do with testing safety standards. Sorry if you got that impression.

I wanted to point out that even the best protected dmm may not survive (work again) if exposed to high energy surges. They will however protect the user.

The video is in no way meant to demonstrate proper safety testing.

It does show the difference in how cheap dmm explode and properly designed dmm contain the explosion.

[joeqsmith]

I watched that video you linked when it first came out and like my own tests, I don't believe you will find it has anything to do with the safety standards.

The video has nothing to do with testing safety standards. Sorry if you got that impression.

I wanted to point out that even the best protected dmm may not survive (work again) if exposed to high energy surges. They will however protect the user.

The video is in no way meant to demonstrate proper safety testing.

It does show the difference in how cheap dmm explode and properly designed dmm contain the explosion.

This is a very specific transient.  At best we can say is how these meters perform against it.   We can't say how these same meters would perform if they were exposed to the surge waveforms called out by 61010.   Trying to tie the two together in anyway will just add confusion.   Worse, it can give a false sense to the beginner that a meter is somehow safe when it may not be. 

It would be fun to see all of them, with their stock fuses run through an arcflash test on the current inputs.   But again, does it matter?   It's the internet.   In the real world, I would expect a trained electrician will use the proper tools and beginners don't get to play professionals.   

[DW1961]

I'm just wanting to understand. If the meter can withstand voltage surge and arc flash for the CAT rating without harming the user.

Many forum members have already expressed their view that it is unlikely.

The most practicle way to know is to have the dmm tested by a test laboratory which certify these safety things,  such as UL (underwriters laboratory) - others exist but I do not remember right now.
Quality dmm manufacturers do this for you, you will find that the quality name have the logo of the certifying lab somewhere on the dmm.
These tests are not cheap and that and the engineering effort is reflected in the price.
You get what you pay for!

There are a few exceptions:
https://www.eevblog.com/forum/testgear/heads-up-cheap-multimeter-lidl-uk-(080218)/25/
Around $20 and it has a certified safety logo, some have even checked the lab report.
Safety rating is not great 250V CAT2
The point is that it has been tested by independant lab and verified to protect the user (not the dmm).
The dmm is basically a dt830 in a larger form factor.

BTW even the quality name brand dmm may not survive

Near the end, Dave blows up a classic Fluke 70, it does not survive but the dmm contained the internal explosion (apart from the flying knob  ) FYI these 70 series 1 predate the CAT ratings.

Yep, watched that video last night. I'm much less interested, and really not interested at all, if the meter can survive after a surge or arc, but user safety.

The main reason I posted is because of questioning wheter or not a 35.00 meter with a CAT III 1000V rating and CAT IV 600V rating can protect the user when hit with over voltage/current.

[DW1961]

I'm not trying to tie him up. I'm just wanting to understand. If the meter can withstand voltage surge and arc flash for the CAT rating without harming the user. The problem is that in order to get that information, without assuming it, is to find someone with a voltage spike machine and spike it with 8000V while the leads are in the current or other than voltage or hit it with whatever current it is suppose to be able to withstand and see what happens.

At what level?  The typical internet Wiki level?  From the EE level? The designer?  The safety inspector? The people writing the standards?  The people running the tests?  ...  I would imagine to be an expert in safety for handheld meters, you would make a career out of it.   

The voltage spike machine is a combo generator.  There are both current and voltage waveform requirements.   I am not aware where the surge or burst are applied to the current inputs.   It would seem rather dumb as you would be shorting out the generator, blowing the fuse before the test even starts. 

It's a good question.

The understanding level I was looking for was from a consensus of authority, whether or not this MM would protect the user up to its CAT rating.

I have the authority with all of you, but not the consensus.


Also, I got the same impression as you did that this 'test' does not say much about how a meter will survive like it should.

[DW1961]

I just wanted to be sure that you didn't have greater expectations of what the the seller, Amazon etc. would do. As I said, there is sometimes some satisfaction to be gained from winding up particularly persistent phone scammers and dodgy sellers, but it's unlikely that it will ever get past that individual, it can be fun though.

I do and did not. I was hoping to have something concrete as evidence that I could report is DEFINITIVELY not CAT certified. However, that definitive evidence has proven elusive.

[DW1961]

I watched that video you linked when it first came out and like my own tests, I don't believe you will find it has anything to do with the safety standards.

The video has nothing to do with testing safety standards. Sorry if you got that impression.

I wanted to point out that even the best protected dmm may not survive (work again) if exposed to high energy surges. They will however protect the user.

The video is in no way meant to demonstrate proper safety testing.

It does show the difference in how cheap dmm explode and properly designed dmm contain the explosion.

That's what I would be interested in also, not if it can survive, but if it protects the user.

[Gyro]

That's what I would be interested in also, not if it can survive, but if it protects the user.

There is also the tricky question of whether you actually want it to survive (operationally)...

1. Can you be sure that its performance and calibration are unaffected (without sending it in for calibration)?
2. Can you be sure that its protective components haven't been damaged to the point that it would not protect the (a future?) user in a future similar event?

[joeqsmith]

I just wanted to be sure that you didn't have greater expectations of what the the seller, Amazon etc. would do. As I said, there is sometimes some satisfaction to be gained from winding up particularly persistent phone scammers and dodgy sellers, but it's unlikely that it will ever get past that individual, it can be fun though.

I do and did not. I was hoping to have something concrete as evidence that I could report is DEFINITIVELY not CAT certified. However, that definitive evidence has proven elusive.

That's easy enough to find out but you won't get it playing on the internet.   Just contact what ever agency/s you are interested in and have them provide you with a quote.   Going through that process would be a VERY good learning experience, especially if you wanted to work in the industry.   

The understanding level I was looking for was from a consensus of authority, whether or not this MM would protect the user up to its CAT rating.

Even if you were able to filter out enough opinion to form a consensus, you shouldn't expect that suggests you have good answers.  It's an open internet forum.  You may feel better about it but that's about the extent of it.   

[E-Design]

I just wanted to be sure that you didn't have greater expectations of what the the seller, Amazon etc. would do. As I said, there is sometimes some satisfaction to be gained from winding up particularly persistent phone scammers and dodgy sellers, but it's unlikely that it will ever get past that individual, it can be fun though.

I do and did not. I was hoping to have something concrete as evidence that I could report is DEFINITIVELY not CAT certified. However, that definitive evidence has proven elusive.

DW1961

Concrete evidence,

Buy 2 of the meters. take one apart and discover its bill of materials. Look up the likely offending parts (fuse comes to mind and any silly sot-23 clamps etc..) Decide on some number of components are possibly in violation and have an effect on the CAT testing/compliance..

Send the second meter with the components and your findings to a 3rd party test house. Pay them.  Have them do full CAT and safety compliance testing and evaluation of it. Get that report and hand it to the MFG legal dept if there is one - along with Amazon and the governing body in the US for consumer product safety.

Otherwise, really!  all you have is a lot of mixed opinions ranging from sensible to wild speculation. A lot of great anonymous web forum people here-- oh and some photos along with more speculation of the circuit design. If you want to get real about it - then get real about it. You are not going to be able to DEFINITELY say much about anything without your own real evidence.. not sure why you would think otherwise.
I think the folks on this forum are great and have high expertise in the matter  . Sadly, not good enough for you seeking concrete evidence.

Are you going to go and tell the MFG they 'likely' dont meet a CAT standard (here is a link to a web discussion)
or
will you tell them they have demonstrably  FAILED the CAT standards they claim - here is a test report filed with Amazon legal dept, and US consumer safety.

eh?

[floobydust]

It's as easy as the manufacturer providing the 61010 certificate of conformance, in backing their claim "Safety Rating EN61010-1,-2-030 EN61010-2-033, EN61326-1 CAT III 1000V, CATIV 600V". "Certification: CE,ROHS,EMC etc."
Dongguan Habotest Instrument Technology Co.,Ltd shows one for their voltage detector. What about their multimeters?

You can also find the 61010 CofC for UniT multimeters, some tests seem to uh have been glossed over. At least they make the effort. It's common-place and low cost to get products safety approved in china, it's just that here you don't have to, so they don't bother. The test process can also be corrupted, as one multimeter popular here on the forums has 61010 approval only as a 3V battery-powered appliance, never connected to anything with a voltage source.

OP gives a picture and asks "will this bridge collapse?" manufacturer claims "supports 1,000 elephants" and well, it's missing most of the trusses so I know it can't do it and it was stuffed elephants on the bridge lol.

[DW1961]

OP gives a picture and asks "will this bridge collapse?" manufacturer claims "supports 1,000 elephants" and well, it's missing most of the trusses so I know it can't do it and it was stuffed elephants on the bridge lol.

LOL, exactly.

Well, I do have some concrete evidence that I didn't before, guys, thanks to all of you.

1. It does not have any MOVs in it.
2. Second, the current fuses are not 1000V.
3. No PCB guard tracks.
4. No Case Blade protection.
5. Small PTCs.

Conclusion: weak protection, but inconclusive as to harm to user.

And, that's how I framed it in the review. I've done the most I can do for an Amazon review. If I were getting paid hourly to investigate, you can be assured I'd do what you all suggested and get the facts on it asap. However, I have to do other things too. I've done x10 more than any other reviewer has on Amazon. I'm pretty over it, as of now.

As always, thanks for all of the insight and help.