Cheap DVM with believable CAT rating ?

[stuarth]

Many times on here and elsewhere, it is said that the CAT ratings of cheap meters are self certified, and may not be trustworthy. Hence, where safety is paramount, you should buy from Fluke or other reputable makers who ensure proper safety testing has been done.

I recently bought a digital clamp meter from Lidl for £14.99 which claims to be CAT III 600V, certified by TUV Rheinland. Looking up the TUV ID number on the Lidl packaging on the TUV website returns the model number on the back of the Lidl Parkside meter. Does this make the CAT rating of this meter just as trustworthy as the rating on more expensive meters? And perfectly acceptable for use on anything downstream of the domestic consumer unit (which is what it was bought for, I have literally dozens of older meters with no safety rating).

Lidl also sell a “normal” DVM for a couple of quid less than the clamp meter version, but that meter is only rated at CAT III 300V, and it uses a PP3 rather than 2AAA cells, so the cost difference is lost the first time you need to buy it a new battery.

Stuart

[Phil__G]

My own view is that good test equipment should last a career and beyond. Buy cheap, buy twice. Or, buy once - buy Fluke
The expense of PP3s can be avoided by simply making a rechargeable one from two discarded vape cells. Most of my non-critical stuff runs on recovered vape cells

[The Philpott]

...Also one wonders about the distinction between using the clamp meter function, or using the test leads...does the certification recognise this distinction? Probably not?

I was measuring the current coming out of a PV array the other day with a clamp meter which is 'cat III 300V', fully aware that the cable was carrying 500v or thereabouts. I wasn't worried about it as i've seen the thickness of the insulation.

Incidentally this particular (Uni-T) meter cost more than the Lidl ones Stuart mentions. M.Hennessey's teardown was critical of the separation between terminals at the business end of the PCB, hinting that it's primarily a clamp meter that has other tricks up it's sleeve.
It's quite miniaturised inside, i don't imagine it being a friend for life, but it's ok for the moment.

Dave

[kalee20]

Originally Posted by stuarth

I recently bought a digital clamp meter from Lidl for £14.99 which claims to be CAT III 600V, certified by TUV Rheinland. Looking up the TUV ID number on the Lidl packaging on the TUV website returns the model number on the back of the Lidl Parkside meter. Does this make the CAT rating of this meter just as trustworthy as the rating on more expensive meters

I'd say, yes it's credible. Unless Lidl have got a load of counterfeit meters and copied the model number from the genuine meter that TUV assessed - but I think that's unlikely, Lidl is a brand that's here to stay, they'll protect their reputation and integrity.

As a meter, it may have cost-cuts in many areas, cheap plastics for the moulding; LCD's that fade after a few years; zero trimming and calibration; and be generally built down to a price. But I can't see safety being compromised.

As for buy cheap, buy twice - i keep a few cheap tools and neters simply to take out in the field, to use in dirty environments (such as on the car), on the basis that if they get damaged, it's not a big loss. I have a Parkside DMM from Lidl for just that reason and I'd consider it excellent value!

[stuarth]

Well, it has CAT III 600V printed both alongside the test sockets and on the current clamp jaws, so it seems they have recognised the distinction.

I have a Uni-t AC/DC clamp meter which claims CAT II 600V and CAT III 300V and a Proskit MT2017 which claims CAT II 1000V and CAT III 500V, both of which I’m suspicious of, the Proskit for example has glass fuses (not HRC) and no slots in the PCB.

I also have a Metrix MX1, an analogue meter which claims CAT I 1500V, CAT II 1000V and CAT III 600V, and a GMC Metramax 12 which claims CAT II 600V and CAT III 300V. These are reputable manufacturers and I’d trust their CAT ratings.

The Lidl meter seems solidly built, 6000 count, true RMS, fast responding continuity buzzer, etc, and you can disable the auto-off timer by holding down one of the buttons as you switch it on. Doesn’t feel like a cheap meter. Like others, I wanted a cheap meter for dirty jobs around the house, inside domestic appliances etc. Since these jobs are where spikes and transients are higher than on the bench, I’m looking into CAT ratings.

Stuart

[The Philpott]

Yes, just looked, and the Uni-T has the CAT legend duplicated on the clamp..

[dglcomp]

Lidl stuff is usually pretty decent and I would trust the fact that it has been TüV certified. My Lidl meter I brought earlier this year seems decent enough, especially given how little it cost.
The only slight annoyance it the meter probes have shrouded tips that can't be removed but that'll be part of it receiving it's certification.

[Craig Sawyers]

The thing that marks a meter that will explode in your hands or be safe is down to the fuses and circuit features.

The cheapo ones use typically 15mm glass encapsulated regular fuses. As such, a meter like this is a death trap, regardless of what is printed on the front. Leaving it switched to say resistance and connecting to mains might well cause it to burst into flames. When held in your hands.

A decent meter will use high rupture capacity fuses - and they are expensive. Fluke has an 11A one for high current range and a 440mA one for low current. They are around a tenner each. The idea being that they will rupture even under massive overload (they are rated as being able to break 10kA completely safely if you do something daft - like leaving the meter in current mode and then connecting to the meter tails.

They are 35mm long and 10mm diameter.

The thing that determines safety in high voltage or high energy situation is routed flash barriers between + and - in the circuit board, and fusible resistors and voltage clamps as backup.

And if you intend on doing mains voltage measurements at the meter tails you need the correct probes. Not to do so risks arc flash, basically a plasma ball, which causes life changing injury.

Which is all to say - buy Fluke. And buy the right probes for the job.

Craig

[The Philpott]

....and have respect for 21st Century dirty tricks. Buying something and finding it satisfactory, then buying another example 5 yrs later may lead to disappointment..It's almost analogous to the price stability of washing up liquid- the price doesn't change, but you realise the bottle has shrunk by 10% since your last shop. (Catering for persons with smaller hands, hmm.)

No fuse in the Uni-T- just 3 MOVs and 2 PTCs, incidentally.

Dave

[G6Tanuki]

I wonder just how many of the AVO8 enthusiasts realise that their meters are potential uncertified death-traps when compared with modern stuff?

I'm happy to use Lidl-style meters for sub-500V applications. Yes they're cheap and cheerful but at least - unlike a Fluke - I don't weep when I leave one of them out in the orchard for a week during a rainstorm, or on the roof of the car and drive away.l

[Wellertcp]

I really cannot understand why people get so worked-up (I've seen it on other forums) over CAT ratings.

CAT ratings refer to equipment used to check/measure mains voltages in an industrial/commercial setting; substations, switch-gear, dis-boards, control panels, motors, etc.

This is a hobby-based forum covering radios, TVs, hi-fi, audio, etc.
~ Why does anyone need to measure the mains voltage, it's either there or it isn't.

[G6Tanuki]

"Mains voltage" is kinda tame compared with what many of us deal with.

Today I've been working with a valve amplifier whose power-supply delivers 690V at 300mA when loaded. Off-load the supply goes up to 800V.

Valve TVs similarly have lots of EHT stuff flying around, and often the only thing between their HT-rail and the power of the National Grid is a diode!

[stuarth]

Working on the bench, the available current into a short circuit and the surge voltages are more limited than those at the house wiring level. Operating voltages, as opposed to surge voltages, are a different matter. I’m happy with most of my meters for bench work, although I don’t have a digital meter I’d be happy to use at 1000V and above, that’s where an AVO comes into its own. For bench work, I like to use meters such as the Unigor meters, or a Simpson 260 with a -p suffix, these have very effective overload cut-outs.

The CAT ratings become important as you move into the house wiring or high power appliances such as ovens, where voltage surges, and misuse such as measuring the resistance of the mains, can be very damaging. As I understand it, the CAT rating are more to do with preventing injury to the user, even if it damages parts inside the meter such as the fuses.

I think the small/cheap ceramic HRC fuse in UK mains plugs is rated for 6kA rupturing capability. Should be good for anything downstream of the consumer unit. We’re only talking about CAT III here. CAT IV on the supply side of the consumer unit might justify a meter with a more expensive fuse. I don’t have a meter with a CAT IV rating.

I know Proskit and Uni-t meters do not have HRC fuses. I’ve not opened my Lidl meter, I don’t want to destroy the sealing label. If TUV are to be trusted, they will have checked it for its ability to explode in your hand on CAT III circuits, and they will have more expertise on safety issues than a quick peep from me would give. Hence my original question.

Stuart

[kalee20]

Originally Posted by G6Tanuki

I'm happy to use Lidl-style meters... at least - unlike a Fluke - I don't weep when I leave one of them out in the orchard for a week during a rainstorm, or on the roof of the car and drive away.l

Oh you've driven off with one on the roof? My Fluke DMM was on the (curved) bonnet. I'd had it 12 years!

I wouldn't trust the insulation and the probes of many a cheap meter, but I would a Lidl-special.

[Oldmadham]

Originally Posted by G6Tanuki

I wonder just how many of the AVO8 enthusiasts realise that their meters are potential uncertified death-traps when compared with modern stuff?

I'm happy to use Lidl-style meters for sub-500V applications. Yes they're cheap and cheerful but at least - unlike a Fluke - I don't weep when I leave one of them out in the orchard for a week during a rainstorm, or on the roof of the car and drive away.l

AVOs aren't "handheld" devices unless you are Godzilla!

If a DMM blows up in your hand, you are a lot closer to the "Bang!", the case is just soft plastic, offering very little mechanical protection, so you can cop the whole impact.

An AVO 8 is made of heavy Bakelite, so that any explosion is largely confined to the inside.
Creepage distances are large compared to the tiny PCBs in DMMs.

The normal operating procedure with AVOs is to place the meter on a convenient surface, set the range, check the leads are in the correct sockets, then place the test leads.

The "biggie" for all meters, if you can possibly arrange it, is to connect the test leads in a fixed position, with the supply OFF .
Step back, turn the supply ON, take your reading, then turn the supply OFF again.

You are usually better than 300mm away from the AVO meter face when using this method.

Since getting into Electronics in the 1960s, I have seen exactly ONE AVO 8 which had been damaged by incorrect connection to the Mains.
The Bakelite body had not been breached at all, although the meter was ready for "meter heaven".

AVOs were built before the rise of the "certification industry".

It's a bit like asking for the maximum Mach number of a Sopwith Camel!

Further, AVOs weren't "idiot proof", as people using them did the unthinkable---learnt the proper procedure for their use.

[Oldmadham]

Originally Posted by G6Tanuki

"Mains voltage" is kinda tame compared with what many of us deal with.

Today I've been working with a valve amplifier whose power-supply delivers 690V at 300mA when loaded. Off-load the supply goes up to 800V.

Valve TVs similarly have lots of EHT stuff flying around, and often the only thing between their HT-rail and the power of the National Grid is a diode!

The thing with "Mains voltage" is that if you are messing around with the feed coming into your building, the current it can deliver is much higher than you can expect from a transformer type power supply in an amplifier.

690v at 300mA sounds a lot, but Australian valve TVs used a centre tapped version of that ("345v a side") combined with a full wave rectifier, pretty much as standard.
Thousands of TV Techs worked on these over decades, with much less salubrious meters than an AVO 8, with a distinct lack of injury.

EHT in valve TVs only needs to supply a small amount of current, so its regulation under higher currents is poor, & the voltage drops radically.

I have never been able to get my head around the fixation on transformerless designs in the UK & other places, which required special series valves, complex insulation & so on, all to save the cost of a measly power transformer.

OK, I understand that there were areas with DC Mains, so they had to be catered for, but it seems everywhere else with normal AC Mains then had to pay for special designs for those few places.

I guess Australia was fortunate, in that, when we ramped up valve production massively during WW2, we concentrated upon conventional 6v & 12 v valves, so odd heater voltages were only available as imports.
Transformers were not at all expensive, so the standard "cold chassis" power supplies reigned supreme, initially with radios, then with TVs, until the advent of SMPS, which if properly designed, still offer a "cold chassis'.

[ppalped]

When it comes down to safety, it is important to make sure that whatever is claimed by the manufacturer for any type of equipment, that it really reflects the actual truth - and this might not always be an easy task. This is one of the reasons why choosing a decent, well-known brand is sometimes easier and ultimately, safer. This is specially true if the environment where such tools would be used can pose any kind of risk to the health or life of whoever will be using such tool in such environment.

But one important thing to remember, is that even using a Fluke doesn't mean you are safe - you might be safer, but not safe, as safety is so much more than relying only on quality tools. Ideally, a very good safety standard procedure should be designed and implemented in such a way that even if a multimeter burns and explodes, you'll have little to no injuries from it. Avoiding that a multimeter fails in such a way should just be the cherry on top of the cake.

That being said, I'm a Fluke fan - not only because if you buy it from a reputable distributor you are assured that it will meet the claimed safety standards, but more importantly (and apart from some newer models and markets they are entering into), their well-known models rarely fail. But when they do, they are (most of them anyway) covered by a lifetime warranty - this is something you won't get if you buy it second-hand, and even more important: You never know what the previous owner did with it.

There are other cheaper brands, such as Brymen, that seem to be highly regarded in terms of safety - but I cannot vow for their quality compared to Fluke, as I witnessed them failing in really funny ways in my hands, and when the 1 year limited warranty expires (2 years if you make a lot of noise with your supplier), you'll end up with a very good paperweight.

Alex

[winston_1]

Originally Posted by Phil__G

My own view is that good test equipment should last a career and beyond. Buy cheap, buy twice. Or, buy once - buy Fluke
The expense of PP3s can be avoided by simply making a rechargeable one from two discarded vape cells. Most of my non-critical stuff runs on recovered vape cells

Interesting. Where does one get discarded vape cells? I don’t vape nor do
I know anyone that does.

[Terry_VK5TM]

Flukes 'lifetime' warranty only exists until seven years after a product has been discontinued and only on products manufactured from 1996 on.

Then it's out of warranty.

[ppalped]

Originally Posted by Terry_VK5TM

Flukes 'lifetime' warranty only exists until seven years after a product has been discontinued and only on products manufactured from 1996 on.

Then it's out of warranty.

Yes - It's a common misinterpretation on "lifetime warranty" - It doesn't mean the lifetime of the owner or the product itself, but the lifetime of the product support/manufacturing cycle, or until Fluke ceases to exist - whatever comes first. It is under warranty while it is still being manufactured. In case of Fluke lifetime warranty, they extend that for a few years after the product is discontinued. Still more than any other manufacturer - and Fluke is known to keep the same models for decades, otherwise military customers wouldn't be buying from them, as process changes are quite costly.

Alex