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Member postings for Robert Atkinson 2

Here is a list of all the postings Robert Atkinson 2 has made in our forums. Click on a thread name to jump to the thread.

Thread: Multimeter recommendations
26/09/2021 20:13:22

SafeBloc was different brnd and design from Keynector.
Keynector looked, as the name implies, a bit like 3 piano keys, You flipped back an isolator at the rear, pressed the bak of the key and the frony opened.

The Safebloc had the isolator contacts in the flip-up lid. Under the lid were 3 more conventional metal clips, These are much further back from the edge of the cover than keynectors contacts. Thus safer with less chance of a stray live strand sticking out.
The Safebloc does not look as nice, but it is safer and you don't have to strip back as much of the outer sheath.

I have examples of both.

Robert G8RPI.

Edited By Robert Atkinson 2 on 26/09/2021 20:14:43

Thread: Heatshrink sleeving as a heat insulator for valve handles?
26/09/2021 15:56:34

ATUM of similar glue lined hestshrink is not a good idea as the glue will soften with heat.
Silicone rubber tube is a good option. The only issues are that it tends to be thick wall and most types have poor resistance to oil and grease.
If you want to try heatsink I'd suggest Raychem DR-25. This is a durable thick wall tube and will give reasonable insulation. As Calum points out it can loosen with time. The best solution for this is to use a thin layer of epoxy under the heatshrink. Try it without and if happy but it loosens replace it and use epoxy.

Robert G8RPI.

Thread: Multimeter recommendations
25/09/2021 17:27:51
Posted by Michael Gilligan on 23/09/2021 16:49:59:

Despite the ‘no longer available’ message … my local Aldi has these in stock at £9.99

**LINK**

https://www.aldi.co.uk/ferrex-digital-multimeter/p/801179390763400

Has any forum member tried one ?

MichaelG.

Panel says "CAT III" and "300V max" which is impossible. Probably not safe for use on mains and counterfiet CE marking.

Robert G8RPI.

13/09/2021 08:15:14

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.

12/09/2021 22:43:03

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.

12/09/2021 19:49:42
Posted by SillyOldDuffer on 12/09/2021 16:55:36:

Posted by Robert Atkinson 2 on 11/09/2021 13:00:40:

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 Functi
on/ /Range Selector to all
possible settings while connected to the maximum rated source.”

Robert G8RPI.

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!

devil

Dave

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

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.

12/09/2021 19:34:55
Posted by Nicholas Farr on 12/09/2021 13:35:37:

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.

scan_20210912.jpg

Regards Nick.

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

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

Thread: Help identifying some tools
11/09/2021 13:06:18

The Bundenburg dead weight tester should have a matching set of weights. normally thes are paired to the tester. Unfortunatly they often go missing...
With the weights it has some value.

Robert G8RPI.

Thread: Multimeter recommendations
11/09/2021 13:00:40

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 Functi
on/ /Range Selector to all
possible settings while connected to the maximum rated source.”

Robert G8RPI.

11/09/2021 12:03:48
Posted by SillyOldDuffer on 11/09/2021 11:07:55:
Posted by Robert Atkinson 2 on 11/09/2021 09:24:44:
Posted by duncan webster on 10/09/2021 20:13:23:

...

The problem with using 250V fuses is that they don't meet the 600V CAT rating of the meter...

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.

Thread: I dont think its 3phase but what is it ?!
11/09/2021 10:00:50

At a guess it a network and power feed to a shed or garage. Whatever it is it is WRONG.

1/ Box should be sealed.
2/ Data and power should be separate.
3/ Choc blocks are not OK for data or for poer in an unsealed box.
4/ wrapping choc block in tape just traps any water that may get in making it worse than without tape.

You need to get that looked at by someonewho is competent and has cable tracing equipment.

Robert G8RPI.

Thread: Cutting Steel Plate.
11/09/2021 09:49:34

Angle grinder.

Unless you have a gas axe (oxygen / fuel torch) and know how to use it. If you did I don't think you would have asked the question though.

Robert G8RPI

Thread: Multimeter recommendations
11/09/2021 09:24:44
Posted by duncan webster on 10/09/2021 20:13:23:

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.

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.

10/09/2021 20:34:35

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.

Thread: What to drive a J & S with ?
10/09/2021 18:51:40

To be clear, a PROPER rotary converter is fine in terms of torque ripple (smoothness) etc but they tend to be large, noisey and power hungry. Modern VFD are now cost effective even without the reduced power consumpton. The "static" converers based on capaitors and possibly step-up transformers do not provide proper 120 degree phase shift so cause torque ripple.This can have adverse affects on surface finish and possibly machine reliability.
There is really no reason for not using a VFD or fixed speed solidstate single to 3 phase converter these days.

Robert G8RPI.

Thread: Multimeter recommendations
10/09/2021 17:45:36

Also see:
https://www.eevblog.com/forum/testgear/a-list-of-multimeters-that-do-not-appear-to-meet-their-claimed-safety-specs/

note " The main criteria is that all inputs must be able to withstand the maximum CAT ratings in all modes of operation, connected incorrectly or not, without harming the user. Current measurement protection must meet the CAT voltage rating as well, in other words fuses used must be rated for the maximum CAT rating on the meter."
I forgot to include the unfused current range in my earlier post..
Your Maplin is on the list " Any Meter with the model number "830" All of these low priced meters are junk just waiting to blow up in your hand. "

Robert G8RPI.

10/09/2021 16:59:47
Posted by SillyOldDuffer on 10/09/2021 10:50:17:
Posted by Robert Atkinson 2 on 09/09/2021 19:41:50:

SOD's picture of a Maplin meter is typical of a "830" type meter sold under many brands fron a few pounds up. Better than nothing, but not safe for use on mains or high energy circuits.

...

Robert G8RPI.

Is Robert's; 'not safe for use on mains' statement personal opinion or evidenced fact? I ask because the meter claims IEC61010-1 and CAT II on the 600V range, and, as it was sold with a CE mark by a reputable UK supplier, I've no reason to believe it's a fake. Can't take it back now if it's a wrong 'un!

dsc06498.jpg

I don't suppose the meter on ohms would survive being connected to the mains, but I don't think it's fundamentally unsafe when used as per instructions. What's the failure mode? If the 200mA fuse failed, I think the fine PCB tracks would fuse inside the box ; the instrument fails safe, unlike the much more heavily built AVO which depends on a 60 year old thermal cut-out.

The cheap meter's 10A shunt isn't a simple loop: the shunt has a notch full of solder and is presumably it's own fuse. Not quite the Widow-maker Robert fears. Whether all examples of this generic type of meter pay the same attention to detail is another question!

Dave

PS. I agree the Maplin meter is too flimsy for working on switchgear!

There is no way that the meter pictured is CAT II 600V compliant. This is a FACT. I can 100% from just one obvious feature - the 20mm glass fuse. No 20mm plain glaas fuse is capable of safely breaking the fault current on even a domestic electrical supply. Compare with the sand filled thick wall ceramic fuse in a 13A plug.

To satisfy yourself pull the fuse and see if it is rated for 600V AC. I bet it is not. For example Farnell do not list a single 600V 20mm fuse
https://uk.farnell.com/c/circuit-protection/fuses-fuse-accessories/fuses/cartridge-fuses?st=20mm%20fuse

The clearance and creapage on the input connector sockets and fuse also appears inadequate but I'd have t measure it to be sure.

The blob of solder on the 10A shunt is not a fuse. it's probably an attempt to calibrate the 10A range after they filled the notch in their first attempt too deep. It could also just be a random blob of solder, or a blind copy of another meter without knowing why it was there or any attempt at calibration.

Robert G8RPI.

Thread: What to drive a J & S with ?
09/09/2021 20:37:20

Any kind of capacitor fix or converter will cause torque ripple and will not be suitable for the spindle motor.

With modern prices there is no reason not to use a VFD. This can be st to 100% speed with a gentle rap up and down. Smaler, lighter, quieter, cheaper and uses less electricity than a rotary converter.

The pump could use single phase with a Steinmetz capacitor arrangement see:
https://electronics.stackexchange.com/questions/424068/3-phase-motor-running-on-single-phase-using-steinmetz-delta-connection

or swap the motor to a single phase one. However fitting a separte small VFD wll allow you to control the speed of the motor and thus the coolant flow. less noise and waste.

Robert G8RPI.

Thread: Multimeter recommendations
09/09/2021 19:41:50

SOD's picture of a Maplin meter is typical of a "830" type meter sold under many brands fron a few pounds up. Better than nothing, but not safe for use on mains or high energy circuits.

The reason cheap meters give a 10A DC range is because it is easy to provide an inaccurate, unprotected 10A range (it's the loop of wire next to the input sockets in the picture). Conversly it is expensive to provide an accurate and protected 10A range.
Likewise the expensive meters don't provide a "transistor test" function because it won't meet the safety requirements due to the small spacing on the socket.

Robert G8RPI.

08/09/2021 21:26:07
Posted by Paul Kemp on 08/09/2021 20:12:56:
Posted by Robert Atkinson 2 on 07/09/2021 17:36:49:

I think the fact it was new out of the box says it all. Presumably a manufacturing defect that was not picked up. Calibration is done with low energy sources for safety so may not pick up all faults. They cetainly don't test the fuse breaking current on every one or they would shi with blown fuses

What did Fluke say when you sent it back to them?

Robert G8RPI

I don't think it was a manufacturing defect, whe I said new out of the box that day it was that morning, the incident occurred in the afternoon. We had been doing a survey with the Class Surveyor to renew the Class cert and leccy had used the instrument on other tasks prior quite successfully both LV DC and HV AC. I suspect Andrew has it right, he simply had it on the wrong setting, it had been a long refit and everyone was tired. It never got sent back, we sailed the next day and never really found enough of it to send back! My point was they can be blown up.

Paul.

But that is the whole point. A meter that is CAT approved will NOT "blow up" even if connected to a supply (within it's rating) on the wrong range. A good one like a Fluke should not even have signficant damage, just a blown fuse. The fuse should not even emit a flame or sparks, that is why they are so expensive.
So either:
A. The meter was faulty nd should have been returned to Fluke if for no other reason than to ensure it was nor a defect that warranted a recall.
or
B. The system it was used on exceeded the meters CAT rating.

Note that the CAT rating is not just voltage, it the available energy i.e. the voltage and the source impedance. It you short out the mains at the end of a mains lead the energy is lower then if you d the same at the consumer unit This is because the resistance and inductance limits the current.
If the meter was being used on a main distribution board for a MW sized generator (possible on a ship big enough for classification) then it may have been being used beyond it's rating. Typically at that energy level the test leads have to be fused as well as the meter.

Robert G8RPI.

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