| 61010-1 | Safety requirements for electrical equipment for measurement, control, and laboratory use — Part 1: General requirements |
| 61010-2-030 | Particular Requirements for Equipment Having Testing or Measuring Circuits |
| 61010-031 | Safety requirements for hand-held probe assemblies for electrical measurement and test. |
| 61010-2-032 | Particular requirements for hand-held and hand-manipulated current sensors for electrical test and measurement |
| 61010-2-033 | Particular requirements for hand-held multimeters and other meters for domestic and professional use, capable of measuring mains voltage |
And, to my surprise, I haven't been able to find any meaningful differences. ...... (All of this is excluding CAT IV 1000V of course, which has no equivalent.) Sure, they specify the difference in intended use, which is more than enough to keep me from using a CAT III meter for CAT IV measurement. But I really expected to find something more concrete than that. I was only able to get access to older versions of some standards, so maybe the latest versions have changed or clarified this. I also could have just completely overlooked something. It seems like there must be a difference, otherwise almost every CAT III meter would also be certified as IV.
Many people have noticed that transient overvoltage tests for CAT III ratings are equivalent (in voltage and source impedance) to the next lower CAT IV rating (i.e. CAT III 600V = CAT IV 300V). People also often wonder if a CAT III 600V meter, for example, could be used for CAT IV 300V measurements. The answer is always a resounding "No", which I agree with completely. I don't plan on ever using a meter for something more dangerous than the manufacturer recommends, regardless of what numbers say.
However, purely out of curiosity, I started to wonder what the concrete differences were in design requirements and test protocols between CAT III and the equivalent lower tier CAT IV rating. I spent a while searching through the following standards:
61010-1 Safety requirements for electrical equipment for measurement, control, and laboratory use — Part 1: General requirements 61010-2-030 Particular Requirements for Equipment Having Testing or Measuring Circuits 61010-031 Safety requirements for hand-held probe assemblies for electrical measurement and test. 61010-2-032 Particular requirements for hand-held and hand-manipulated current sensors for electrical test and measurement 61010-2-033 Particular requirements for hand-held multimeters and other meters for domestic and professional use, capable of measuring mains voltage
And, to my surprise, I haven't been able to find any meaningful differences. Clearance, creepage, impulse testing, exposed probe tip length, everything for CAT IV seems to either line up with the equivalent higher tier of III, or in some cases, be less stringent for IV. (All of this is excluding CAT IV 1000V of course, which has no equivalent.) Sure, they specify the difference in intended use, which is more than enough to keep me from using a CAT III meter for CAT IV measurement. But I really expected to find something more concrete than that. I was only able to get access to older versions of some standards, so maybe the latest versions have changed or clarified this. I also could have just completely overlooked something. It seems like there must be a difference, otherwise almost every CAT III meter would also be certified as IV.
I understand the differences in intended use, the available energy at different points in the system, etc. My question was about specific, concrete differences in design requirements and test protocols.If I understand correctly what you asking, there are generally not much stipulations as to design details of instrument (there are some, like separation distances and such). Only tests that it has to survive. It is up to manufacturer to devise design that will satisfy the requirements... Again, as Joe said, what is in the standards is in the standards. No more, no less. What detail is there you have to obey, everything else you have to design yourself. And make it so that it survives the test...
Fault currents are listed in the standards you mention.
I went back through them again and I'm still not seeing anything unique to CAT IV. The overcurrent tests are set at 10 times the device's max rated current, for all categories. The current created during the impulse testing should be the same, since both CAT III and CAT IV are tested with 2 ohm source impedance. Fault current when testing with probes in the incorrect terminals or in the incorrect range should also be the same, since both III and IV are specified to be tested with a 30kVA supply.There is no difference in the testing, as you found out and all meters that can meet CAT III 1000V are also rated for CAT IV 600V.
No. CE is self declared. If you designed to the applicable standards and you tested it internally or externally with a report, then you are good. There's no centralized registrar for certificates, unlike UL/FCC.
I went back through them again and I'm still not seeing anything unique to CAT IV. The overcurrent tests are set at 10 times the device's max rated current, for all categories. The current created during the impulse testing should be the same, since both CAT III and CAT IV are tested with 2 ohm source impedance. Fault current when testing with probes in the incorrect terminals or in the incorrect range should also be the same, since both III and IV are specified to be tested with a 30kVA supply.
Fault currents are listed in the standards you mention.
I went back through them again and I'm still not seeing anything unique to CAT IV. The overcurrent tests are set at 10 times the device's max rated current, for all categories. The current created during the impulse testing should be the same, since both CAT III and CAT IV are tested with 2 ohm source impedance. Fault current when testing with probes in the incorrect terminals or in the incorrect range should also be the same, since both III and IV are specified to be tested with a 30kVA supply.