Multimeter recommendations

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.

Well electrickery is not my deep specialism I was the engineer superintendent on the job, can only recount what I saw. Total available power was four 160kW generators if all on the board at once with the bus tie closed but ship maximum load 50% of the maximum power (100% redundancy) only 2 machines on the board at the time, bus voltage 415v 50hz. Whether a ship is classed or not hasn't much to do with size, this was an 86m ferry but Class can go down to at least 24m. Lots of small vessels are classed and many administrations delegate approval responsibilities to Class. I can't remember the exact test being carried out at the time, probably under or over voltage trips as frequency and reverse power trips were usually done from the board instrumentation, the volt meters on the boards were analogue and not that easy to read small variations.

Paul.

Thank you for the information gents. I am still ploughing through the recommendations and links. Strangely it seems that the cheapo varieties often have more functions than more expensive models. In particular a setting for DC current.

Mick

I was looking at buying a new multimeter myself recently. My 30 year old analog one (Maplin own brand) is still working but accuracy is pretty suspect. The rotary switch is a recurring cause of problems on this and many other meters. I've had mine apart for cleaning on at least one occasion... and need to do it again.

Personally I found the Fluke vs china cheapie question left me thinking that I was really missing something in between these extremes - surely Fluke is not the only decent brand?

I found this article helped to shed some light on the 'middle ground' more than most. It's US based though but some of the brands are readily available on our side of the pond.

I haven't made a decision and the circumstances that prompted the question have now passed so my purchase has been pushed down the priority pile.

... and yes an analog one is nice when you want to look at a moving value... and yes a cheap one is good for use where you don't want to risk damaging your nice one... plus there are circumstances when having two meters on the job can be very useful.

Edited By Andy Carlson on 09/09/2021 08:45:49

… more functions … In particular a setting for DC current.

Possibly, but usually one range to 200mA (fused) and a 10A range (which is not fuse- protected). An excessive current through the 10A range usually means the end of that particular function - and possibly the whole instrument.

Simplicity generally means more reliability. Fewer switch contacts to wear out, for instance. Not all cheap digis have auto shutdown (or don’t actually completely turn off) and often don’t have a low battery warning - the first thing you eventually notice is incorrect readings…

I used to have a standard reference cell and that used to show up the cheap meters for what they were. All the (low cost) digital meters were always fitted with fresh batteries and checked prior to ‘A’ level Physics practical exams.

I purchased a TACKLIFE TRMA 6000 Multimeter at the beginning of last year and it's very good - I'm happy with it, it's a solid well made device. I did a little research at the time and the reviews were all positive in the areas that mattered to me. At about £30 it was also a reasonable price with everything I needed (and more). I still have my old analogue meters but don't really use them these days.

However, I've just checked and it seems TACKLIFE don't sell here in the UK now but they are still available in the US & Italy apparently.

Regards

Hi Andy Carlson, Fluke are more or less at the top end of the market, but they are designed for intensive use for professional engineers, but there are many other brands that do have very good attributes at a more realistic price for general usage, but cheap is cheap and is of limited quality and life span, but there are plenty in the £30 to £40 range that fill the needs of those that don't have to use them for certificated or everyday pro' work. Just look for ones that will suite what you are likely to use them on. Which ever ones you get, make sure you understand how they are to be used correctly and know their limitations.

Regards Nick.

Rather than theorise about 'quality' here's photos of the insides of an AVO8 (Model B) and an inexpensive Maplin Digital.

The AVO movement and electronics are mounted on a thick plastic front panel backed by a heavy steel box, not waterproof. The electronics are hand assembled from separate components of basic type: wire-round resistors, bent springs, open switches, the whole being much exposed. The construction style is a century plus old, and was pretty sensible because the unreliable components of the day often needed repair. (My meter has a few old repairs.) This type of construction is semi-skilled, labour intensive, and extremely expensive: much of the customers money went on wages, not 'quality'. In 1953, an AVO 8 plus leather carry case cost the equivalent of about £700: only an exceptionally wealthy amateur could afford a new one.

The Maplin meter was built using modern mass-production techniques. Few humans involved: most likely the SMD components were automatically placed on the board by a machine and wave-soldered in the blink of an eye.

The meter's brains are in the Integrated Circuit far right in the photo. The electronics are far more complex than those in the AVO, and also far cheaper. Once designed and debugged the IC can be sold in volume for less than a pound. The other components are also mass produced far more cheaply that their 1950's equivalents. The AVO has a seriously pricey high-end D'Arsonval movement; the modern meter has a Liquid Crystal Display costing a few pence.

Not much difference between brands or models when inexpensive meters are mass produced in this way; the old-fashioned notion of quality that applied to my 1950's AVO don't apply to this class of consumer electronics. It's quite hard to make duds provided the meter isn't too cheap. But beware buying manufacturer rejects, customer returns, and damaged goods from unknown purveyors on the web.

Chasing 'quality' is likely to waste the amateur's money on a grand scale! Going up-market takes one into paying serious money for ruggedisation, high accuracy, and safety features designed to save professional electricians from mistakes made on live switchgear.

If you're the type who enjoys owning feel-good tools, by all means buy an AVO or one of its modern equivalents. Just don't pretend it's a rational procurement decision. (I fancy owning a red MG even though it's daft)

Otherwise think about Requirements! Comparing my similar examples:

If carrying the meter in a pocket is important, don't buy an AVO! If AC current is wanted, don't buy the Maplin. If safety is important, don't buy either!!!

Dave

An excellent fact-check, Dave

MichaelG.

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.

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!

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!

I got a nice amateurs unit, a Vichy 99 but they don't seem to sell it here anymore

import only

Edited By Ady1 on 10/09/2021 11:04:18

I bought my AVO8 (Tropical version) in 1959 brand new and it cost me the princely sum of £55. Still going strong today.

Replaced the leads and clips for later versions. Works for me. Throw away cheap meters have their uses however.

About 35 years ago, a short part of my career was spent both using and repairing AVO multimeters.
The company I worked for had several hundred that were on a 6 monthly calibration cycle. If they failed calibration, they came to our department for repair. It could be a very time consuming task depending on the fault. Two faults filled us with dread, one was rotary switch replacement when the contacts wore out, as it was a complete strip down.
The second was the overload cut-out, which was a fiendishly cunning mechanical system that relied on the acceleration of the movement pointer to open a push to reset switch. It was real knack to get this this to trip or not to trip within specification.

Also we went out of "field jobs" outside of the workshop around the factory. If an Avo was needed this went in the basket of a butchers style trade bike as they were damned heavy to carry any distance. Hand held Fluke DMMs were a godsend as they would just fit in a lab coat pocket.

Hi, well here's my line up of digital multimeters, first one is Maplin's precision gold range and must be nearly 20 years or more old. It is cat III 600V and has measured the mains umpteen times without any issue, but there is no current measurements to worry about. I have compared it to a good known professional multimeter at one time and the results were not different enough to be concerned about. It can be seen that it has transistor and capacitor testing, I can't remember exactly how much it cost, but think it was in the £25 range at the time and this was my first digital multimeter I had, previous ones were analogue, which I do still have but rarely use them now.

This next one is a UNI-T which I bought from Maplin's for around £35-£40, a fair while before they closed their stores. It is auto-ranging, but the ranges can be set manually, it is cat IV 600V and cat III 1000V and does have DC and AC current in all ranges but no transistor testing, it has also been used to measure the mains. All the readings compare very well with the above one with no drift worth any mention.

This next one I received yesterday, I really only bought it to save me paying postage costs on another two items, but I chose it really for the battery test function although it seems to be a good general overall use one. This is also cat III 600V and cost £11.94 from CPC/Farnell. Haven't use it yet, so don't know how it compares with any of the two above.

This last one is completely different as it doesn't measure volts or amps but it does have Inductance measuring, resistance, capacitance and transistor testing. I think I bought it about 18 months or so ago and it cost in about the £35 range, again from CPC and it was the inductance range that I wanted. I've measured a few commercially made chokes that have been marked with tolerances on and has been in the same ball-park close enough not to make any effect for what I would use it for. Just have to remember not to put it across any voltage, but it only has leads that are 170mm long including the crocodile clips, so I shouldn't really confuse it with any other meter.

Regards Nick.

Edited By Nicholas Farr on 10/09/2021 13:04:40

When I was working, the company issued the engineers with "Fluke" meters. When I retired, mine had to be returned, so I bought this one from Maplin for about £20 at the time. Since then I have not noticed a difference in performance between this and the Fluke. The same model is currently on sale at Amazon for about £45.

At the other extreme is this one, which also came from Maplin and on Amazon at the princely sum of £9.99

I can't remember how much I paid for it but not a lot. It is very similar in size and shape to the first moving coil meter I ever got (now long gone)

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.

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.

Hi Robert, I'm not disagreeing with you, however this brand new meter from CPC that I have, it states the fuses as being 250V fast blowing, which has been factory fitted with glass ones.

The instructions for my UNI-T say they must be glass fuse 250V fast type.

So have both of these manufacturers got it wrong?

Regards Nick.

Edited By Nicholas Farr on 10/09/2021 19:25:29