Maybe it has already been discussed before in this thread, but I am wondering why there are no cheap Fluke clones with good electrical robustness. Most of the techniques are in plain sight. Just copy the board with big clearances, large fuses and MOVs. It may cost a few more dollars for parts, but the margin for "professional" multimeters is much larger.
Because:
a) There's no need, sales of unsafe meters are doing just fine.
b) Certification costs money and you're not going to sell many meters without certification marks.
c) Once a meter is certified you're not allowed to change a single component supplier or any part of your production line without going through re-certification.
I suspect (c) is a real problem for Chinese meter makers.
[...] several japanese brands (Samwa, Hioki) have excellent quality and reputation and also do not have markings. It boils down to the manufacturer's reputation and seriousness.
[...] several japanese brands (Samwa, Hioki) have excellent quality and reputation and also do not have markings. It boils down to the manufacturer's reputation and seriousness.
No- Sanwa, Hioki etc. will "design to" 61010 but never tested, no approvals, so it's another gamble.
Using gas-tubes for protection is a known no-no because of the follow-through current that exists with real mains-transients. OVC aren't just a high-voltage blip. Once a gas-tube is lit due to a transient, you have mains to deal with afterwards and in the 1/2 cycle arc flash happens, the part explodes.
Now I'm thinking that perhaps, rather than run different brands, take the most notorious brand (Duracell) and just test those to discover the best mechanism for leakage FIRST, before testing all the brands?
And maybe get a bunch of small $2 farting novelty gadgets that takes two AA's that has a small standby current. I could get dozens of these on AliExpress and run various combinations.
Product recommendations?
[...] several japanese brands (Samwa, Hioki) have excellent quality and reputation and also do not have markings. It boils down to the manufacturer's reputation and seriousness.
No- Sanwa, Hioki etc. will "design to" 61010 but never tested, no approvals, so it's another gamble. One spacings mistake and you learn why testing is done in the first place.
Using gas-tubes for protection is a known no-no because of the follow-through current that exists with real mains-transients. OVC aren't just a high-voltage blip. Once a gas-tube is lit due to a transient, you have mains to deal with afterwards and in the 1/2 cycle arc flash happens, the part explodes.
They seem to have no problem putting certification stamps on existing meters, whether outright fake or just shady. With plenty of review sites and videos, it wouldn't be hard to get a reputation for real robustness with a few large protection components.
Let's assume that companies who design DMMs are not stupid enough to place a MOV or GTD directly across the meter's inputs.
Maybe it has already been discussed before in this thread, but I am wondering why there are no cheap Fluke clones with good electrical robustness. Most of the techniques are in plain sight. Just copy the board with big clearances, large fuses and MOVs. It may cost a few more dollars for parts, but the margin for "professional" multimeters is much larger.
Because:
a) There's no need, sales of unsafe meters are doing just fine.
b) Certification costs money and you're not going to sell many meters without certification marks.
c) Once a meter is certified you're not allowed to change a single component supplier or any part of your production line without going through re-certification.
I suspect (c) is a real problem for Chinese meter makers.Fungus, "c" is only valid if you apply for their "listed" program (UL, TÜV, Intertek, etc.). The listing requires annual inspection to the manufacturing plant audits and process reviews. Most Chinese low cost meters do not go through that, but that does not solely explain lack of safety: several japanese brands (Samwa, Hioki) have excellent quality and reputation and also do not have markings.
Let's assume that companies who design DMMs are not stupid enough to place a MOV or GTD directly across the meter's inputs.
That assumption is mostly correct, but in a very few cases it is not.
Which meters have you seen where they did this? Did any of these have some sort of safety certification?
[...] several japanese brands (Samwa, Hioki) have excellent quality and reputation and also do not have markings. It boils down to the manufacturer's reputation and seriousness.No- Sanwa, Hioki etc. will "design to" 61010 but never tested, no approvals, so it's another gamble.Do you work at one of these companies? If not, you can't possibly know that.
As far as the protection circuits with GDT/spark gap, I see most are across the inputs in series with the usual 1.1kohm PTC, like in the 34401a, PM300, and with the extra 1kohm surge resistor for the Keysight handheld DMM'S.
The antique Beckman/Wavetek/Meterman/Amprobe Tech300/3000/HD110 family used 2kV GDT or spark gap directly across the multimeter's input. A bunch of Radio Shack models as well- these are all from pre-1010 era.
Only Fluke had a spark gap after the HV input resistor, back in the day when they used that instead of MOV's.
So an ionized gas tube would give different fault currents, some explosive due to follow-through current, and others much PTC smoke when on a DC bus (where GDT normally extinguishes at zero-cross on mains) where it's a long-term wiener roast due to the tube lighting up and keeping current flowing in the PTC.
Using gas-tubes for protection is a known no-no because of the follow-through current that exists with real mains-transients. OVC aren't just a high-voltage blip. Once a gas-tube is lit due to a transient, you have mains to deal with afterwards and in the 1/2 cycle arc flash happens, the part explodes.
You've probably done more testing and comparison across multiple brands than any manufacturer. Based on all that experience maybe can design your own meter with best protection features and start making it, to compete with EEVblog meter.
For high voltage behaviour even a tiny bit of resistance ( teraohms or more ) counts very much ... sparkgaps have very little as they are phisical gaps , MOV's and the other components obviously have much more . What do we see in the video is discharging in gases vs different dielectric materials . So for easy protection you would want a "leaky" material , obviously not desirable in long term as some degradation would occur . But for a fair test is very important that the equivalent input resistance to ground of the measuring IC is somewhat added after that 10Mohm resistor . I bet it counts very much .
[...] several japanese brands (Samwa, Hioki) have excellent quality and reputation and also do not have markings. It boils down to the manufacturer's reputation and seriousness.No- Sanwa, Hioki etc. will "design to" 61010 but never tested, no approvals, so it's another gamble.Do you work at one of these companies? If not, you can't possibly know that.
Can we stop shilling multimeters from manufacturers such as Sanwa and Hioki, that have no 61010 safety approvals, only misleading statements such as "designed to" or "conforms to" or "safety rating" or "CE" which mean nothing.
Maybe for japanese market is enough and they don't care too much about the rest of the world ...
EN 61010-2-033 defines electrical safety for handheld multimeters.
SAFETY REQUIREMENTS FOR ELECTRICAL EQUIPMENT
FOR MEASUREMENT, CONTROL, AND LABORATORY USE –
The above is from Part 1: General requirements of 61010-1.
Part 2-033: Particular requirements for HAND-HELD MULTIMETERS
and other METERS, for domestic and professional use,
capable of measuring MAINS voltage
The test leads come up from time to time. These are covered in 61010-031.
It is THE document where CAT category ratings are defined as applied to multimeters for measuring mains voltages....
So no, they are not muppets. I trust them much more nowadays than Fluke run by bunch of greedy creeps that are coming from the same school of management as those scumbags that are running Boeing.. You know, taking some of the best and most respected companies in the world, firing all the engineers that made those companies great and milking the brand reputation as long they can, until they destroy it..