QuoteSo, 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.
QuoteSo, 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.
QuoteSo, 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.
Sometimes I get lucky and some unintended area with breakdown (arc) and absorb enough to save the meter from the recycle bin.
The diode-connected transistors clamp the overload hard at first, then the PTC heats up and the fault current backs off.
QuoteSo, 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 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.
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?
QuoteSo, 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.
QuoteSo, 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 just wanting to understand. If the meter can withstand voltage surge and arc flash for the CAT rating without harming the user.
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.
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.
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.
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.
QuoteI 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.
QuoteI'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.
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.
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.
QuoteI 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.
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.
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 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.
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.