QuoteDoes anyone have a Fluke (or other legal brand) they can show images of for a meter of this CAT category and how it should look inside?
Did you not watch the eevblog video nusa posted?
It clearly explains the typical input protection circuits. If I remember correctly, Dave points to the insides of an old Fluke 23 to illustrate.
There are also dozens of dmm tear downs with images in the test equipment section.
Many of them have comments on how safe the input protection is for that dmm.
In general, all the name brand (Fluke, HP/Agilent/Keysignt, Hioki, Gossen, AVO, Brymen, to mention a few) will have proper safe input protection.
Anything cheap (less than 75$) is not likely to have good safe input protection. You get what you pay for.
It is the typical low cost Chinese meter with false claimed cat ratings. This is very common can found on something like 90% of the cheap meters in the US. The fuses are a dead giveaway - proper fuses for CAT 3 1000 V are twice the size and maybe more expensive than the meter. If you see a sub $50 meter with CAT4 rating one can be nearly sure it is fake. With a 1000 V CAT 3 rating it is highly suspicious. I don't know a proper place to report for the US, but it seems like there is no effective system to take those parts with false ratings off the market.
The fuses here are even slightly better than found in many cheap meters - so it maybe OK for a CAT2 300 V rating and thus OK to use with 110 V mains with some care.
It does not really matter if one only wants to do voltage measurements. The typical mistake / accident scenario where you need a proper fuse is to accidentally have the wires in the current terminals when you want to measure voltage.
It is the typical low cost Chinese meter with false claimed cat ratings. This is very common can found on something like 90% of the cheap meters in the US. The fuses are a dead giveaway - proper fuses for CAT 3 1000 V are twice the size and maybe more expensive than the meter. If you see a sub $50 meter with CAT4 rating one can be nearly sure it is fake. With a 1000 V CAT 3 rating it is highly suspicious. I don't know a proper place to report for the US, but it seems like there is no effective system to take those parts with false ratings off the market.
The fuses here are even slightly better than found in many cheap meters - so it maybe OK for a CAT2 300 V rating and thus OK to use with 110 V mains with some care.
It does not really matter if one only wants to do voltage measurements. The typical mistake / accident scenario where you need a proper fuse is to accidentally have the wires in the current terminals when you want to measure voltage.
I have an Amazon brand that is rated as Cat III 600V. It has Klein fuses and a copper shunt wire, but not the fuses you mention. So, Amazon is guilty of marketing these bogus CAT rating meters also.
However, what if you are measuring Voltage correctly, and you get a 3000V spike? Isn't CAT IV III suppose to be something like capable of taking care of a 6-8, 000V transients?
This is really disturbing to me, guys. It just rubs me all sort of wrong ways. It's not right.
Just read through this and others too. The PTCs in this unit are suppose to work as voltage clamps?
https://content.fluke.com/promotions/promo-dmm/0518-dmm-campaign/dmm/fluke_dmm-chfr/files/safetyguidelines.pdf
I have an Amazon brand that is rated as Cat III 600V. It has Klein fuses and a copper shunt wire, but not the fuses you mention. So, Amazon is guilty of marketing these bogus CAT rating meters also.
However, what if you are measuring Voltage correctly, and you get a 3000V spike? Isn't CAT IV III suppose to be something like capable of taking care of a 6-8, 000V transients?
QuoteDoes anyone have a Fluke (or other legal brand) they can show images of for a meter of this CAT category and how it should look inside?
Did you not watch the eevblog video nusa posted?
It clearly explains the typical input protection circuits. If I remember correctly, Dave points to the insides of an old Fluke 23 to illustrate.
There are also dozens of dmm tear downs with images in the test equipment section.
Many of them have comments on how safe the input protection is for that dmm.
In general, all the name brand (Fluke, HP/Agilent/Keysignt, Hioki, Gossen, AVO, Brymen, to mention a few) will have proper safe input protection.
Anything cheap (less than 75$) is not likely to have good safe input protection. You get what you pay for.
Amazon cant be held responsible for ensuring the specifications are met for all the products it allows to transact.
Amazon cant be held responsible for ensuring the specifications are met for all the products it allows to transact.
It's an Amazon brand. They could be held accountable for that.
There are no electrical/electronic component/product safety import regulations enforced in the West. There is no safety watchdog. The chinese are forever opportunists and it's our fault for letting in this stuff. Don't let Peter Navarro know about it.
So the low-end multimeter market gets ruined- legitimate players go out of business because real safety parts and approvals adds cost. The chinese industry is doomed because Mr. Honest now saying Cat. II when liars are saying Cat. IV, they can't go backwards for claims or be competitive. Funny thing is it's not that difficult to fix these issues (protection, certification) but they don't have to.
In the USA it trickles down to employers following OSHA regulations where the safety specs are important, but for the casual user or hobbyist, sellers - it doesn't matter. Wallwarts/phone chargers, Christmas lights, soldering/hot air stations, inverters, DVD players etc. many are not safe. But Amazon has no qualms about selling it.
It's ironic that a trademark infringement had US Customs stopping Sparkfun's multimeter import over Fluke's yellow cosmetics. But safety? let'em products roll in.
Amazon is only concerned about selling counterfeit products. I bought a cheap phone charger and it was terrible wrt safety, the power cord was like a shoelace so I gave it a bad review noting it has no safety approvals and shortly afterwards the brand name vanished and just changed to a different name.
Amazon commercial multimeters, their ones made by CEM (Shenzhen Everbest Machinery Industry Co. Ltd.) have 61010 certification. They use two or three MOV's and big PTC like 90DM600 pics.
I followed OP's multimeter through at least four chinese shell companies, it's kinda crazy how many names and hops are involved.
Amazon is only concerned about selling counterfeit products. I bought a cheap phone charger and it was terrible wrt safety, the power cord was like a shoelace so I gave it a bad review noting it has no safety approvals and shortly afterwards the brand name vanished and just changed to a different name.
Amazon commercial multimeters, their ones made by CEM (Shenzhen Everbest Machinery Industry Co. Ltd.) have 61010 certification. They use two or three MOV's and big PTC like 90DM600 pics.
I followed OP's multimeter through at least four chinese shell companies, it's kinda crazy how many names and hops are involved.
The meter is not legal in the US or Europe. There is no such thing as a 250V voltage limit on current input.
The fuses must have the same voltage rating as the CAT rating of the multimeter.
If the meter is rated CAT III 1000V, the HRC fuses must be rated for 1000V also.
The meter is not legal in the US or Europe. There is no such thing as a 250V voltage limit on current input.
The fuses must have the same voltage rating as the CAT rating of the multimeter.
If the meter is rated CAT III 1000V, the HRC fuses must be rated for 1000V also.
I want to add that to my review because I want to rake this MM on Amazon. Is there a link you have I can use for substantiation? Or, do others here concur this is not even legal in the USA?
The cat rating is definitely bogus. It may still meet some thing like 300 V CAT2, though not for sure.
The fuses may be good for 500 V or maybe 600 V with not that much breaking capacity - so no way to get a CAT4 rating.
The over-voltage protection (especially for the Ohms part) with only the tiny PTC is likely also a weak point, possibly even for CAT2. There is no absolute need for MOVs or visible spark gaps - but it helps.
The limitations on the frequency mode makes me even doubt about CAT 2 with a significant voltage.
Why would you need over voltage protection on Ohms? You mean the over voltage could cross over to the Ohms circuit?
MOV - Mercury Oxide Varistor - they start to conduct at a threshold voltage, thereby limiting the max voltage seen by the dmm
They are the blue things looking like large ceramic capacitors.
Keysight/Aglient (and some other manufacturers) prefer to use a gas discharge tubes to limit the voltage
And the comment about no such thing about 250V rating on current input - that individual doesn't understand the reasoning or design. All meters have a voltage limit on this input despite the low impedance.
The cat rating is definitely bogus. It may still meet some thing like 300 V CAT2, though not for sure.
The fuses may be good for 500 V or maybe 600 V with not that much breaking capacity - so no way to get a CAT4 rating.
The over-voltage protection (especially for the Ohms part) with only the tiny PTC is likely also a weak point, possibly even for CAT2. There is no absolute need for MOVs or visible spark gaps - but it helps.
The limitations on the frequency mode makes me even doubt about CAT 2 with a significant voltage.
Why would you need over voltage protection on Ohms? You mean the over voltage could cross over to the Ohms circuit?No.
A quality multimeter will not suffer any damage (other than a blown fuse in current mode) if connected to a circuit while in the wrong mode, provided you stay within the meter's stated limits. So if, on a meter that's specified to 1000V AC in volts mode, you accidentally connect to 400V AC in ohms, capacitance, mV, or whatever, no damage should occur. Cheap meters lack the protection circuitry needed to allow this kind of insult, and thus may be damaged.
(In contrast, CAT ratings specify the (massive) fault voltages the meter will protect the operator from. For example, a typical industrial meter like a Fluke 87V is rated for CAT III 1000V and CAT IV 600V. Both of those categories specify a transient overvoltage of 8000V, meaning that an 8000V surge will not cause the meter to explode in the user's face. The meter, however, does not have to survive the event in order to comply with its CAT rating.)
The meter is not legal in the US or Europe. There is no such thing as a 250V voltage limit on current input.
The fuses must have the same voltage rating as the CAT rating of the multimeter.
If the meter is rated CAT III 1000V, the HRC fuses must be rated for 1000V also.
I want to add that to my review because I want to rake this MM on Amazon. Is there a link you have I can use for substantiation? Or, do others here concur this is not even legal in the USA?
Those crap designs should get raked on Amazon.
Why not consult an attorney about the actual legalities of it (there are even free legal advise websites) - Everybody else is just providing speculation. Who knows what actual laws are broken (an attorney does)
If you want have a credible legal complaint, you had better have a sound legal basis for it.
And the comment about no such thing about 250V rating on current input - that individual doesn't understand the reasoning or design. All meters have a voltage limit on this input despite the low impedance.
And the comment about no such thing about 250V rating on current input - that individual doesn't understand the reasoning or design. All meters have a voltage limit on this input despite the low impedance.
Specifically, he said that the CAT voltage rating applies to the current circuit as well. Is that a true or false statement?
I was really interested in that because if true, then it is not a CAT certified device. (We don't need to know the laws, then, because the argument is logically true--follows directly from premises to conclusion with no leaps.)