Multimeter recommendations

I've learned something from this thread, always good. Anyone know where I can get fuses for a Fluke at a sensible price?, £10 a pop is a bit ott. It's a type 87 serial 62430186 and on the back it says F 1A 600V, F15A 600V. Interweb searches suggest 11A and 440mA, which seems sensible as they are +10% on the max for each range. It appears something changed after number 65650000. I can't imagine using the lower rating would matter

Clearly BS 1362 fuses are good for 250V AC, how about the DC rating? Or BS2956A 1.25" glass, these have 250V engraved on the end.

Hi Nick,

Yes, either inadvertently or by deception, I can't tell which, they are claiming compliance with CAT standards that they cannot meet.
This may be because they misguidedly do their own analysis of compliance and get it wrong. Even Fluke don't do this, they send their meters for independent verification.

The requirement is that applying a high energy source at the maximum rated voltage to ANY combination of inputs in ALL switch positions will not cause a hazard. A hazard includes shock, sparks or explosion. The amount of energy appiled goes up with the CAT rating number even if the voltage is the same. This is bsed on the FAULT current the supply it is intended to be used on can supply. This can be thousands of amps.

There are two things to note:
1/ This is for protection against spikes or surges on the supply or mis-application of the meter.
2/ The meter does not have to work after the test.

It can be seen that unless there is a problem with the powersupply or the meter is mis-used not having a fully complinat meter has no effect. It's only when something goes wrong that you will find out the the meter is deficient in it's protction. By then of course it is too late.
The big issue is that there is no enforcement of compliance. Trading standards don't have a buget to send meters for testing.

Robert G8RPI.

The problem with using 250V fuses is that they don't meet the 600V CAT rating of the meter. You might know this but what if somone else uses the meter and does not?. Note that the fuse in a meter has to be safe for surges and spikes on the supply so 250V fuses would not pass for a DMM CAT rating by analysis even at 240V nominal mains.

If the fuses need replacing it means someone has made a mistake before and the protection worked, do you want to risk it the next time?

" You got to ask yourself, do I feel lucky? Well do yah punk?"*

Robert G8RPI.

*Dirty Harry 1971, You are playing russian roulette when you use a non CAT compliant meter on mains. Mains has a lot more energy than a 44 magnum.

Hi Robert, thanks for answering my question and with that it is a little disconcerting that a company like Farnell are associated with the sale of these multimeters if they are not up to the category they claim to be. However, I do know the fuses only protect the current measuring sections and I'm highly unlikely to be measuring any amperage on high energy circuits and most likely never on any 3 phase installations.

I have been reading this Fluke Safety Guide Lines which is very interesting, but on page five, they do say to replace any fuses with those that match the manufacturers high energy fuses that they specify. I'm also aware by the presents of the lightning symbol in the triangle on my new meter, that the meter and it's leads should not be handled when high energy circuits are connected, but this was mentioned years ago with my old Maplin analogue multimeters that the meter should be connected while any high energy circuits are turned off and should not be handle during any tests and then removed only when the circuit is turn off again.

Regards Nick.

Edited By Nicholas Farr on 11/09/2021 10:43:24

Is that true, or an assumption? From LittelFuse, who invented them, my bold:

In electronic equipment with relatively low output power
supplies, with circuit impedance limiting short circuit
currents to values of less than ten times the current rating
of the fuse, it is common practice to specify fuses with
125 or 250 volt ratings for secondary circuit protection of
500 volts or higher.

Does anyone have access to IEC61010-1?

Possibly Fluke meters are designed to survive blowing a fuse, whereas the cheaper meters are disposable. In them the fuse protects the operator, not the instrument, which goes in the bin.

What's the most destructive test I could put my spare M-0830B too? With suitable precautions I'm tempted to blow it up deliberately! Could be wrong, I think it's light construction will cause the board to pop inside the case rather than explode or catch fire. Pity Maplin have gone bust and I can't ask them: be good to see their documentation justifying the CE mark.

Dave

Hi Dave,

The line you quoted "In electronic equipment with relatively low output power supplies, with circuit impedance limiting short circuit currents to values of less than ten times the current rating of the fuse"

Is the key.
We are not talking about electronic equipment or low impdence circuits limiting currents, we are talking about MAINS SUPPLIES and their ability to supply currents in the thousands of amps before the supply fuse opens.
And no, a RCD does not help because we are talking about live to neutral currrents. The only thing limiting the peak current is the circuit impedance which is a fraction of an Ohm. Even the 10A shunt in a meter is typically 0.01 Ohm so peak current across the mains(at 240V RMS nominal) is roughly 34,000 amps (240x1.414 / 0.01) Actully a bit less due to wiring imedance etc, but it's still thousands of amps.. This is assuming you connect the meter across the mains on 10A range by accident which is what CAT ratings are about.

Robert G8RPI.

Dave (SOD) also said " I think it's light construction will cause the board to pop inside the case ..."

I agree, and that would be a failure of the CAT test. A flash arcing) caused by vapourising a conductor is considered a hazard. That is why high breaking current (not fusing) rated fuses have sand filling and tough ceramc or composite bodies, to contin the flash.

I've carried out high energy discharge tests and you don't want to be on the wrong side of the safety screen!

From IEC 61010-1
"16.2 Multifunction meters and similar equipment
Multifunction meters and similar equipment shall not cause a HAZARD in any possible combination
of RATED input voltages, and settings of function and range controls. Possible HAZARDS include
electric shock, fire, arcing and explosion.
Conformity is checked by the following test.The maximum RATED voltage specified for any function is applied to each pair of TERMINALS in
turn, in every combination of function and range controls. The test source connected to the
equipment measuring TERMINALS during this test is limited to 3.6 kVA for measurement category I
or measurement category II. For measurement category III or measurement category IV, the test
circuit has to be capable of delivering 30 kVA.

During and after the tests, no HAZARD shall arise.
Multifunction meters and similar equipment are to be tested by changing the Function/ /Range Selector to all
possible settings while connected to the maximum rated source.”

Robert G8RPI.

Hi Robert, for your information, this is the card that was in the packet that my new multimeter came in, which claims it's conformance of EN61010-1 CAT III. All I can do is accept what it says.

Regards Nick.

Edited By Nicholas Farr on 12/09/2021 13:44:31

Excellent to see what IEC 61010-1 actually says! I think it can be read two ways, one of which is Robert's strict interpretation, the other much less onerous. As Devil's Advocate:

First, the successful test is one in which there is no HAZARD. I argue this means it doesn't matter what happens inside the case provided the explosion, fire and arc are contained and can't physically harm or shock the operator. A hand grenade could be safely exploded inside a sufficiently strong box. The contents would be completely wrecked, and the box bulged, but I claim it's a pass.

Secondly, what's meant by 'The maximum RATED voltage specified for any function is applied to each pair of TERMINALS in turn, in every combination of function and range controls.'? I could argue it doesn't mean 600VAC must be applied to all the terminals and switch settings. For example, my less rigorous interpretation is that the maximum RATED voltage on the 200mV DC range function is only 200mV, not 600VAC. Not difficult.

Thirdly, the input energy of a CAT I or CAT II test is limited to 3.5KVA, which is far less than a sand-filled mains fuse has to cope with. Even if the meter disintegrates inside the box, 3.5kVA isn't spectacular unless the current continues to flow. I argue there's no particular reason why it should, and in practice all those thin PCB tracks will break almost instantly. It's another pass.

Just a hypothesis. Though I suggest an overloaded M-830 would still fail safely, with minimum HAZARD, I don't know! However, if my sophistries are correct, it might explain why weedy multimeters are CE marked and equally acceptable for sale in the USA and all other administrations around the world. They can't all be fakes can they? Maybe IEC 61010-1 isn't that demanding, or perhaps all the testers have been bamboozled by smart lawyers!

Dave

PS. I actually sympathise with Robert's line on electrical safety: in practice I'm pretty careful with volts and amps.

I've bought the proper fuses for my Fluke, found them at £5 each. At least my widow will be able to sue Mr Fluke if I get blown up.

It would be interesting to get Farnell and RS comments on this thread, but I'll not hold my breath

Perhaps the clamp ammeter is the way to go? No high current clearing needed, just the ability to withstand 1000V on an uninsulated wire.

Hi Nick, I assume that paperwork came with t "STANDARD" ST913 in your earlier picture. If that is the case I can say it is incorrect just from your picture. Theis is because there is no CAT rating next to the input terminals.

Additionally the paperwork does not reference a model number and the make of the meter in the picture does not ppear to be STANDARD. If you read the link I posted earlier there are ots of meters that dont meet the declared CAT standard. Did the suppliers catalog or web listing actually state it was CAT III 600V?

Likewise your UNI-T UT61 is non compliant because the rating has only been appled to the Volts/ Ohms terminals. A meter has to pass on ALL inputs and functions to be compliant. Current ranges are harder than voltage to make compliant.

Manufacturers and suppliers make all sorts of incorrect or plain fradulent claims.

Robert G8RPI

Hi Dave I think it is clear that it is the maximum CAT rated voltage that has to be applied. Thus if a unit is CATII 600V even if the equipment specification says 500V max, the test applies 600V. Also the same voltage is applied to all termin combinations on all switch settings. This is common sense as there is nothing to stop the operator setting up for current measurement and then connecting between live and neutral instead of live and load. In safety terms this is a "slip" and has to be expected.
The hazard of arcing includes internal arcing. If this was not the case Fluke etc would not use expensive fuses designed to contain the intentional arc of them fusing. An uncontained arc can lead to other hazards.
No "830" meter is really safe for use on the mains.

Robert G8RPI.

Hi Robert, this is the one that I purchased from CPC/Farnell.com TEN01061

This is the front page of the instructions, it doesn't have the standard or the ST-912 printed, but all the specifications printed inside match what is stated on the front of the meter.

The test leads supplied have CAT III 1000V CAT IV 600V and also the CE and the double insulation symbol and 10A with the Earth symbol, moulded into both of the probes.

Regards Nick.

Edited By Nicholas Farr on 12/09/2021 20:29:51

As far as l am concerned , l am with RA all the way on this one . Regulations , and their literal interpretation , whether simply in the form of a code of practice or statutory , exist not to keep someone in a job but because at some point in the past someone has been hurt or even killed , and you ignore them at your , or worse someonelses peril .

In the event of an untoward occurrence , and you're in front of the man with the silly wig on , or the men from the ministry ( HSE ) and the inevitable question is asked " Do you have a code of practice , and have you followed it ?" you'd better have a bullet proof excuse if your answer is likely to be "no" . BEEN THERE , DONE IT , and it's not a comfortable place to be even when your answer has been " yes".

So well done RA for giving the benefit of your experience and advice so freely and without personal preduice , which with luck will help someone being injured or killed .

On a more specific aspect , is the CE mark shown in the supplied pictures and actual CE mark ( indicating compliance to known standards) or , as been noted in the past simply Chinese Export which just happens to be in the same type face as the genuine CE mark ?

Trevor .

Well both CPC and Farnell list Tenma for that model number but that supplied to you and pictured on their websites is branded "STANDARD" The claim on the website is they meet IEC1010 (no dash number or date specified IEC1010-2 is for centrifuges) not EN61010. The IEC 1010 standard is obsolete and is replaced by EN 61010-1. (the latest version of 61010-1 also requires compliance with parts of EN61010-2-30, another document to buy).

You could ask CPC for evidence of the meters compliance, but they are just taking the suppliers word for it. Am almost tempted to buy one and challenge it. CPC sell "retail" so I could go to Trading Standards.

The slightly more expensive Duartool DO3144 loks better at lest it quotes 61010-1 band the manual specifies 600V 10kA breaking fuses, but the tepmerature / HFE input is not protected to 600V (manual page 4 f says 250V. https://www.farnell.com/datasheets/2648510.pdf ) So that is also a clear failure.

There is a reason why compliant meters cost more. Caveat Emptor and if it looks too good to be true it probably isn't.

B.T.W. checking compliance of aircraft parts is part of my day job. A few years ago I found that ta safety compliance test of a electrical component had not been done correctly in two respects. The test intention is actually similar to part of EN 61010-1. This was an exsiting part and thouands are fitted to airliners.The part maker agreed that the test had been done incorrectly and neither the approved independant test house, the part maker or the aircraft mnufacturer had noticed! They re-ran the test, but did it wrong again! The got it right on the second re-test. Fortunatly the part passed or there would have been a huge re-call required. The tests cost in the 5 digit range.

Robert G8RPI.

Hi Robert, thank you for your assessment, however I won't pursue CPC for any evidence as they probably won't know anything more than what is in the instructions, but the instructions are well written although fairly basic, but they do point out the hazards and to use it with caution and it is unlikely that it will be used in a situation that will have any danger and as I've said, I really only got this one for the battery test facility and it was in effect half price as it covered postage cost for the rest of the same order. At least this discussion may help others to choose carefully what they buy for their own use.

Regards Nick.

Edited By Nicholas Farr on 13/09/2021 07:50:47

Hi Nick,

That is fine. As long as it is just your personal use and you have assesd the risk and accepted it. This is like so many other things in ME which would never be allowed in a commercial or industrial setting.
I'm not trying to be the "safety police" . I just want people to have correct information so they can make that informed judgement. There ais a lot of poor information oout there. Regulations and guidance also evolve and what was "OK" last year may not be today.
For anyone using meters in any kind of commecial or public environment they really should be fully compliant. As Trevor says you might just hve to answer for your actions. Also if you have insurance they may quibble about it and not pay you or try to claim back off you for a 3rd party payment..

Trevor,
Thank you for your comments. On CE marks, the one on SOD's "830" meter is incorrect but it might be an old meter. Those shown by others appear to be the correct mark but unless the item is fully compliant they are not valid.
Interestingly. if you want to sell into China they do not accept CE UL etc. You have to submit samples and full technical details to a test house in China and pay for testing. Somone cynical might say that clones would be on the market before you approval was granted.....

Robert G8RPI.

My advice if you are buying a budget meter is chuck the leads away and buy a decent set. Personally I would be more worried about flimsy probes that anything that was going to happen to the meter itself.

regards Martin

Whoa whoa fellas!

£10 for a fuse? Divide £10 by the number of years until you next blow a fuse - in my case I replaced the fuse in my Fluke 77 with the correct Fluke fuse about 10 years' ago - so it has cost me just £1 per year so far, and I haven't blown it again yet, so that price drops every day.

Why are you trying to use a cheap substandard part? There is a saying from my aviation career; "if you think safety is expensive; try having an accident".

For all we know, genuine Fluke fuses might be filled with nitrogen or other inert gas, or expensive compounds, to ensure its reliability and safety.

For what it's worth:

1. For a safety critical part; use the correct, genuine, manufacture's specified part.

2. Divide the cost of anything by the number of years it will last or that you will use it for.

3. Even though you might not use the meter in a critical situation, your son, or a friend who borrows your meter one day, might do. (Or you might forget that you put a cheap fuse in and endanger yourself).

4. Fluke meters are a quality item. Why cheapen it and compromise its safety performance by trying to save a few quid?

5. Do you use the cheapest available brake pads on your car, or the correct OEM ones? (actually, don't answer that.....!)

.

Edited By John Doe 2 on 23/09/2021 11:13:27

Edited By John Doe 2 on 23/09/2021 11:15:34