Cheap multimeter accuracy

[SUNRAY]

Could you edit the link please, the bracket has somehow been included!


In the our labs we regularly check our meters against a bench meter that we keep calibrated, and we have very few major discrepancies.
We have hundreds of Flukes, but for a mid range choice, I can recommend Tenna/Uni-Trend meters - they seem relatively student proof!

How I managed to include the bracket in the link I have no idea, My process for avoiding such problems is to type the 2 brackets : () then past the link between them. Anyway edited.
I've had a fair bit of dealing with Tenna products as CPC sell them and to date they have all been spot on, the exception being the hall effect clamps need to be positioned 'just so' whereas a proper iron transformer doesn't suffer that same problem.
I used to get their 'fag packet size' meters from CPC when they cost about £2 but stopped getting them when the price shot up.
I currently have 3 of these:

which I find very useful and useable, I think I paid just over £30 with the VAT at various times, over the years I've sourced over a dozen for other people after they've used mine.

 

[RandomGrinch]

I've had a fair bit of dealing with Tenna products as CPC sell them and to date they have all been spot on, the exception being the hall effect clamps need to be positioned 'just so' whereas a proper iron transformer doesn't suffer that same problem.

We have a purchase system based on consortium suppliers providing specific products - this is ok for 'everyday' items, but can leave you a very limited choice when buying more specialist products.
Our consortium supplier for test equipment provides decent discounts, but only on high-end products.
CPC/Farnell is one of our consumable suppliers. I have saved a lot of time and faff by sneaking through the odd (well, maybe many!) CPC order with an obfuscated description - hence some well used, but illegitimate Tenmas in the lab!

 

[plugwash]

I don't know where you work but I remember being told at the University where I work that anything below a certain value was considered a "consumable", we certainly buy low value test gear from our electronic components suppliers frequently.

As far as I can tell Tenma is a Farnell group house brand selling re-baged kit from a number of Chinese manufacturers. When I looked at the address on the box, it matched exactly to an address of another part of the Premeier Farnell Group (IIIRC the now defunct MCM electronics in the USA). You can often find the real manufacturer by googling the part number.

I did have a Tenma insulation resistance tester (a rebranded uni-t) that I was not particularly happy with, It's under-range indication was easy to misunderstand, and the lower limit of it's range was too high if testing to the limits of BS7671.

That particular model is no longer sold, but I think if buying a house-brand meter I'd want to do some tests on it to determine it's limitations before trusting the results. Resistors, even with Ludicrously high values (I bought a 1GΩ resistor to test said IR tester with) are cheap.

 

[opps]

In the our labs we regularly check our meters against a bench meter that we keep calibrated, and we have very few major discrepancies.
We have hundreds of Flukes, but for a mid range choice, I can recommend Tenna/Uni-Trend meters - they seem relatively student proof!

Thanks will check them out.

 

[blup]

Big clive does a youtube teardown/ comparison of cheap and professional multimeters, a key difference is the quality/size of the fuses, so its this additional safety you are paying for i.e. if things go badly wrong.

Blup

 

[JohnW2]

Big clive does a youtube teardown/ comparison of cheap and professional multimeters, a key difference is the quality/size of the fuses, so its this additional safety you are paying for i.e. if things go badly wrong.

Interesting. I must say that no matter what corners were being cut (to reduce cost) with the cheap ones I would not have expected that the size/quality of fuses would have been one of the main things to suffer.

Of course, the relevance of that issue depends upon how sensible/careful one is. In what must be about 60 years of using multimeters, I don't think I have ever caused a fuse to blow (or blown up a meter, despite any fuses that it might have). As for 'safety' (to persons, not of the device), although 'nothing is impossible' it must be incredibly rare for something significantly dangerous (to humans) to happen to a meter, no matter how silly or careless the user.

I think that one has to try to put these things in perspective, because of the incredibly range of prices. There is a fair choice of DMMs available for £3-£4 or so (and countless under £10 or £20), yet some which literally cost 'hundreds of pounds' (at least one Fluke costs over £850), so I think one really has to critically ask whether the cost of the latter (or even 'intermediate-rice ones, say £50 - £150) can really be justified.

Kind Regards, John

 

[plugwash]

The problem with traditional multimeters is they have a current measurement range involving the leads. In electrical work this range is both rarely useful and a big liability. Bottom of the barrel mulitmeters will often have the high-current range completely unfused and the low-current range protected by a fuse with low breaking capacity. Better multimeters will have both current ranges fused with fuses appropriate to the meter's safety rating. For a CAT IV meter those fuses can be quite bulky and expensive.

Personally if you are buying a meter purely for electric work I'd look to a clamp meter rather than a traditional multimeter.

 

[JohnW2]

The problem with traditional multimeters is they have a current measurement range involving the leads. In electrical work this range is both rarely useful and a big liability. Bottom of the barrel mulitmeters will often have the high-current range completely unfused and the low-current range protected by a fuse with low breaking capacity. Better multimeters will have both current ranges fused with fuses appropriate to the meter's safety rating. For a CAT IV meter those fuses can be quite bulky and expensive.

I understand and agree with all that. However, as I said, I think one has to consider whether that difference can justify paying 10 times, or even 100+ times the price, particular given that, as I said, I would think that the true 'safety' risk (risk to life and limb) is probably incredibly small - and the 'risk' of destroying a £3 - £15 meter is obviously trivial..

Personally if you are buying a meter purely for electric work I'd look to a clamp meter rather than a traditional multimeter.

That might make sense. What would also make sense (for 'electrical work') would be to omit at least the high-current range, and maybe all current ranges' (very rarely used for 'electrical work' - or, perhaps, to have some sort of 'interlock' to prevent one switching to a current range 'unintentionally'.

For me personally, what you suggest would probably not be a good idea, because my meters tend to be used far more for 'electronic' than for 'electrical' work (but, even then, only rarely for measuring current, and hardly ever for measuring high currents)..

Kind Regards, John

 

[RandomGrinch]

Of course, the relevance of that issue depends upon how sensible/careful one is. In what must be about 60 years of using multimeters, I don't think I have ever caused a fuse to blow

When you have a number of Fluke 23's in a student lab, you get used to changing 440mA fuses!

I think one has to consider whether that difference can justify paying 10 times, or even 100+ times the price, particular given that, as I said, I would think that the true 'safety' risk (risk to life and limb) is probably incredibly small - and the 'risk' of destroying a £3 - £15 m

My considerations for multimeter purchases may be quite different to a lone electrician, and aren't based on any safety risks!
Although some considerations may not be obvious. None of these reasons necessarily justify the huge prices differences, but hey ho!

Consistency - we already have hundreds of Flukes. I can buy a 115 today to replace an old 111 - and importantly for us, no experiment scripts would have to be changed.
Similarly for year groups, we want to introduce equipment in the first year that will be familiar through to their graduation; from familiarity comes proficiency!

...and even further than that, ideally we will be using the same equipment that they will find in a research environment.
Hence a lot of Fluke, Tektronix and Agilent kit makes its way into the teaching labs.

Reliability - The Flukes have been bullet proof for us. Although the rotary dials need some contact cleaner every so often.
They just 'Thud' satisfyingly, if they fall off our tall benches

Quality - this is an odd consideration.
Students are paying a lot of money for their course and want to see that money being spent well. Even though I could fill the lab with cheap multimeters and equipment, the students would be wondering where their money was being spent, even if it was being utilised better elsewhere! There is a fine line to tread, and the 'touch points' that students interact with need to be of a certain quality.

A down side to Flukes - apparently they are eminently steelable!
One visiting rep was really surprised that we had so many Flukes out on the benches - another university he had visited, had disposed of all of theirs, because they just kept going missing!
Not a problem for us, so far

 

[JohnW2]

When you have a number of Fluke 23's in a student lab, you get used to changing 440mA fuses!

That doesn't necessarily surprise me - but I am certainly not (and I doubt that any of the others in this thread are) working in a 'student lab' environment. On the contrary, I (and probably most of the others) are talking about meters which will only ever be used by one (non-student0 person or, at most, a very small number of (non-student) people!

My considerations for multimeter purchases may be quite different to a lone electrician, and aren't based on any safety risks!

I can understand that, and everything I've said obviously relates to very different environments from yours.

Students are paying a lot of money for their course and want to see that money being spent well. Even though I could fill the lab with cheap multimeters and equipment, the students would be wondering where their money was being spent, even if it was being utilised better elsewhere! There is a fine line to tread ..

OK, but might that not work both ways? - in other words, some of the more 'thinking students' may feel that they are being asked to pay what they regard as excessive amounts of money for their course because ludicrous amounts of money are unnecessarily being spent on equipment, when very much cheaper products would probably serve the purpose.

Kind Regards, John

 

[EFLImpudence]

Plus - Random turning up in designer brand clothes rather than F&F.

 

[JohnW2]

Plus - Random turning up in designer brand clothes rather than F&F.

Quite so!

Kind Regards, John

 

[Justin Passing]

@RandomGrinch - what/whom do you teach?

I wouldn't belittle the extra functions you get on a more expensive meter.
There's quite a list- off the top of my head;
- auto ranging
- manual ranging selection
- true RMS
- more digits or part digits
- Fluke style analog display
- AC current, often missing, or low current range missing
- very high current range (10A+)
- high voltage range (say 1kV)
- diode test
- No huge steps in the ranges
- auto switchoff with beep
- max hold
- reading hold
- auto hold on measurement change(Fluke style)
- 2 leads sockets vs 3
- a stand,
- a hook
- a magnet
- a rubber enclosure to protect it
- a decent carry case Fukes used to come in a nice tough box. Used meter and case was £30 on ebay for a long time.
- a display light
- protection against all manner of mis-connection

- capacitance
- frequency
- square wave output
- temperature by K-type TC
- transistor hFE test

Plus more which I can't think of. Nobody needs ALL those, but my goto meter has many of them, and it was £25.

 

[flameport]

Consistency - we already have hundreds of Flukes. I can buy a 115 today to replace an old 111 - and importantly for us, no experiment scripts would have to be changed.

That is by far the most common reason that Fluke devices are still purchased in volume at their high prices.
Large corporations and the military don't want the hassle of changing thousands of existing processes and procedures every year or four. They want consistency, and that's what Fluke provides. They also want the availability of replacement devices which is just a case of buying some more - no changes to specification or anything else. The cost of the devices is irrelevant when compared to the multiple millions that changing processes and retraining would incur.

For the average user, there is little or no benefit to buying an expensive Fluke meter over plenty of others.
Some of the older Fluke products are significantly inferior to devices from other manufacturers in both specification and features.

 

[RandomGrinch]

OK, but might that not work both ways? - in other words, some of the more 'thinking students' may feel that they are being asked to pay what they regard as excessive amounts of money for their course because ludicrous amounts of money are unnecessarily being spent on equipment, when very much cheaper products would probably serve the purpose.

Yes, maybe - but there's also an issue within the sector; with competition between institutions, on open days, prospective student visit days and publicity materials, a lab full of Lidl multimeters wouldn't quite cut it!
Many institutions end up with a certain 'quality' of equipment, because that's what others have.... and that's not necessarily best value for students.

There are also a lot of 'Sponsored' labs appearing at the moment, for example another department has a lab sponsored by NI LabView - with much equipment provided at low or no cost. This may be good value for the students, but I find the ethics questionable!

Plus - Random turning up in designer brand clothes rather than F&F.

F&F for me, sports cars are more my thing!