Which Digital Multimeter?

[threeseven]

It would seem logical that having the skill to reverse engineer to that extent, that they would instead just design and sell their own products.
Anyway, the Chinese are now facing the same problem as the West, their labour and infrastructure rates are rising fast so they won't have the luxury of such a massive price advantage for much longer.

[Craig Sawyers]

It would seem logical that having the skill to reverse engineer to that extent, that they would instead just design and sell their own products.

Getting off-topic again, but...

You have to be very careful applying Western logic in pacific rim countries. As an example, at one stage I was on a business visit to Japan, and Honda showed us their biotechnology facility. This was as sophisticated as I had ever seen. "What sort of products are you manufacturing here?" I asked. There was a pause "No products" "Pardon me - so what is this facility for" "Because we want to learn about biotechnology"

Likewise second guessing what the Chinese mind-set is regarding plagiarising products is fraught with problems. The difficulty in dealing there, in my last job we were trying to sell our product into China, and appointed a Chinese agent to act on our behalf. Even so two years on (I've since left the company) not a single product has sold - they make it as difficult as they possibly can, and put up hurdle after hurdle to discourage sale non-Chinese products in China. We had to supply units we for approvals testing (and CE/UL is not accepted there). They even made it a requirement that we supply mechanical drawings and software code as a prerequisite of approval. Yes - you read that right.

[threeseven]

Good point. It's easy to forget cultural differences when not in regular contact with them, even quite close to home.
I have a friend who went to live and work in France, she was astonished at how different and even outright strange business practices were there.

[MrBungle]

Did some research. What we all really want is a Heathkit IM-2215, which is an ICL7106 based bog standard DMM, almost an 8020A rip off, with schematic and assembly info, with Fluke style input protection.

Schematic link: http://tubularelectronics.com/Heath_...M-2215/sch.jpg

Edit: to be clear, it needs Fluke style input protection added, not that it comes with it!

[threeseven]

I have a Heathkit IM1202 nixie tube DMM, still works but I wouldn't expose it to high voltage!

[MrBungle]

Always wanted one of them. Have precisely no use for it other than the "ooh" and "ahh" factor though.

[G6Tanuki]

I've read this thread with interest.

My one-and-only DMM is a £9.99-from-Screwfix one. Marked as "CAT III" I'll happily use it for general testing on stuff up to and including 350V, even though it supposedly goes up to 600V.

I *did* once use it in a situation where there was 550V at around 1A to be measured - but in that particular case the meter was sitting inside a RF shielding cage with safety-interlocks on the access so no way was it touchable when the HT was on. The biggest issue I had doing this was getting the cage access-door closed, the HT warmed-up, and taking a reading before the meter's auto-power-down kicked in.

A cheapie DMM has other advantages too: I once left a Bird-43 RF Wattmeter on the roof of the car. It wasn't there at the end of a 300-mile motorway journey and I had to pay for the replacement out of my salary. I won't fret too much if the dog decides to use my £9.99 Screwfix-Special as a chew-toy.

[threeseven]

Originally Posted by MrBungle

Always wanted one of them. Have precisely no use for it other than the "ooh" and "ahh" factor though.

It's quite interesting internally, shall we say, quite tightly packed!

[G0HZU_JMR]

I think there is a bit of snobbery going on here!

Not really, it's not snobbery to criticise the OP's cheap Chinese meter that costs under £3 new from Farnell... I would definitely want to upgrade from this meter if it was my only DMM. I'm almost certain that this is the same meter that was given out as a freebie DMM with every order by one test equipment supplier we use at work.

I think that I have three different classes of meter here at home. By far the worst is the cheapo TMK meter I pictured earlier. This is probably better than the Duratool meter but not by much. It's fine for occasional use on low voltage low power stuff even though it feels cheap and flimsy.

But go up a class in meter and you can buy the modern equivalent of my old Maplin Precision Gold DMM that I bought in the 1980s. This meter was a fairly decent hobby meter and I chose it carefully at the time. It has a fairly decent amount of protection built in and was marketed as being overload proof to something like 500V AC/DC across all ranges using various protection circuits. i.e. you can select the wrong function/range and it will (presumably) tolerate this up to 500V without permanent damage.

It's not in the same class as a Fluke in terms of build quality, precision or ruggedness or protection but I trust it for measuring 230V AC inside equipment and I've used it up at 500V DC when testing my old Tek 585 scope many years ago. I wouldn't trust it to survive misuse in the same way a Fluke meter can but this meter is a decent and reliable tool for home use. It has survived about 30 years' daily use and I'm amazed that I haven't worn out the range selection switch by now.

If I was a student again today the modern equivalent would probably be something like the Eevblog/Brymen meter. This meter is in a similar price bracket allowing for inflation, it has similar features (usually slightly better than my old meter) and it has a USB interface and decent protection built in. Not sure it will be as hardwearing as my old Maplin meter but modern electronics gear isn't made like this anymore.

My other meters are professional DMMs that I bought used. There are obvious risks when buying a used meter but I'm pleased enough with these meters as they were relatively cheap. The Fluke 45 only cost me £35 on ebay.

I would guess that the typical choice today would be between the Eevblog/Brymen meter or a basic Fluke meter. If I was a student on a budget and I wanted lots of features and good protection I'd buy the Eevblog meter but if I was looking to buy a meter to withstand a lot of use and last a long time and be reliable in terms of accuracy then I'd pay a bit more and consider buying a Fluke meter.

However, I'd avoid the Fluke 115 because it only resolves down to 1mA and the 116 version looks better in this respect. However, the specs for accuracy are best described as "adequate for most tasks" rather than impressive. My 30 year old Maplin meter has better specs for accuracy and I don't think I've ever adjusted it for accuracy on the DC or AC ranges since it was new. I have tweaked the thermocouple calibration a couple of times but that's it. But it still reads 10.00V the same as my pro bench meters on DCV. (but then again so does the little TMK meter and that hasn't been adjusted since I bought it many years ago at a rally)

[threeseven]

Just a tip for those testing mains and 3 phase as a routine, there is a test device known as a Drummond MTL 10 or 20. This is designed to safely test on mains and 3 phase installations and equipment. It indicates in voltage bands of 50, 100, 200, and 400+ upto 500, AC and DC through a scaled indicator lamp.
Check it out on their website.

[McMurdo]

By far the worst is the cheapo TMK meter I pictured earlier

go up a class in meter and you can buy the modern equivalent of my old Maplin Precision Gold DMM

For a time, TMK made Maplin's precision gold meters!

Mine dates from the late 80's and is still going strong without repair. It's my main 'home' meter. I bought it before I started work and used it there for a few years before it was replaced by the aforementioned fluke I smashed. (BTW there wasn't a rubber case available for my model).

[G0HZU_JMR]

Interesting...

Your TMK meter looks to be better built than my TMK meter here. I bought this one as a factory reject at a rally maybe 15-20 years ago. It was in a large box with dozens of the same meter all priced at £1 each. All the meters in the box had display faults and I think I just had to clean the display interface to get it to work OK. I chose this one because it 'worked' when I squeezed the case...

It has proved to be a surprisingly stable/accurate meter but could my TMK meter be a fake? It says made in Korea on a sticker on the back.

I haven't taken my Maplin meter apart for a very long time but see below for an image I have just taken of both meters. The top of the case of the Maplin meter is reluctant to lift any higher than this because it has wires going into the top half.

But I think it's clear that there is a gulf in build quality between the two meters in the image. The Maplin meter looks to be well made with decent quality parts in the meter and it has more than one PCB and some decent EMC shielding and it has various protection devices in the front end.

[McMurdo]

Mine looks quite like yours but the battery/fuse is horizontal. No reason to suspect it's fake, I think it comes from a time before that sort of thing was so widespread. They did them in brown too. Not a bad little meter, think mine retailed at around £30 (rubber case was extra). We used to get them in for repair (yes they were worth doing!!!) from industrial users. Usual thing was poor contact through display rubbers or buckled switch wipers. They're clearly influenced by the Fluke 70 series.
I think TMK (UK) who supplied spares & diagrams later morphed into DiLog Instruments, who are still trading.

[G0HZU_JMR]

For completeness here's an image of the other side of the PCB. I'd expect Dave Jones' speech to go up an octave if he were to comment on this meter but it is still working after all these years. It does have an easy life because I mainly use it for DCV checks on low voltage stuff. Even the 250mA fuse is original. It's going to need a new PP3 snap soon though.

The rotary switch feels cheap and flimsy and the whole meter has that twisty, squeaky, flimsy feel you get with low cost stuff bought from a pound shop. But it does work well as a cheap and fast auto ranging meter when probing around various test points on a typical low voltage circuit board. I would expect that it would only take one fairly basic connection mistake to stress and damage the rotary switch though overload. The wafers look like they are on the cheapo PCB and it all looks very flimsy to me.

[G0HZU_JMR]

I spotted this video on youtube that tests the Eevblog meter for voltage overload with various transient tests up to several kV.

https://www.youtube.com/watch?v=g3uYcHAumhA

I didn't watch all of it but the meter does seem to be designed to survive some fairly nasty transients. I wouldn't volunteer any of my meters to go through those same tests...

It does look like this meter would cope quite well inside various types of vintage equipment allowing it to measure typical HT/anode voltages and still survive against some nasty transients. It would certainly be a huge upgrade from the £5 meter but only if you actually need or value the extra protection and features/specs it offers. As I said earlier, I think this meter would be on my shortlist if I was starting again and buying a decent and versatile DMM for home/hobby use.

[Craig Sawyers]

That is a comprehensive review - thanks for posting