Maplin Multimeter: how to use?

In message , Chris Oates writes

Mine would rise from his grave if he thought you might be eating something which he isn't

rats !! of course in 'many worlds' he wouldn't be totally dead anyway

To Martin and Geoff,

The real value of a "transistor tester" would have been in the days when transistors in the UK were germanium, "alloy diffused" types, with a wide spread of gain, which was low anyway and cost 2 weeks pay as a paper boy, but a bagfull of out of spec. devices could be bought relatively cheaply.

Sadly, 2 points arise. In 1961/2 the Maplin 5 Quid Multimeter wasn't available and if it had been I wouldn't have had the 5 Quid to buy it.

DG

A layman's explanation I have heard is that making an observation opening the box "Collapses the wave function" of the cat.

Bad news for the cat.

I can think of several classes of circuitry upon which, making an "observation" with a "Maplin 5 Quid Multimeter" might well have their wave function collapsed.

DG

Generally true. A quick 'diode test' on the two junctions and a wet finger to the base gain test is usually enough in the domestic environment.

Either way, these £5 are good value and perfectly good for most DIY use.

With respect, I would advise you to go and read BS EN 61010 and GS38

Yes the volt meter would be fine if only ever used on volts. It is what happens when things go wrong, with a meeter that has been designed to cope with the short circuit current, then there is little problem. If not there is signficant risk of injury. For interest look here

James Salisbury B.Eng(Hons) MIEE

neither I would think, is a 15W bulb

mike r

In message , James Salisbury writes

Scary stuff and there are of course risks with anything. The probability of getting run over is, I would think higher than the scenario you outline above.

If the device is approved in the UK to be used to test mains voltage, then it is approved to test mains voltage. Sure, it's better to use e.g. a Fluke with well spec'd test leads (as I do) but then there's always a quality / price trade off. It's the same with cars, a Fiesta is liable to come off much worse in an accident than a rugged 4X4. Are you going to tell people not to drive Fiestas because they are less safe ?

Geoff Drage B.Sc (Hons) MIEEE

Presenting a low impedance to a high current source with your hands is always a bad idea - much better to use a clamp meter. I can't ever remember using a probed meter on Amps except on SELV gear Better to kill the power and start injecting your own & use Mr Ohms to figure out whats going on

Glass at high temperature will conduct anyway

IIRC there are more injuries from arc flash than contact electrocution

Most people think a 13A fuse blows at 14A

You'd surely use crock clips if measuring current on mains? And insulated ones? Of course decent ones are unlikely with a cheap DVM.

Trouble is that many things have a very different resistance when cold, so Mr Ohms would only be guessing.

Isn't this how Sir Clive made his first fortune? Buying a bulk load of "failed" transistors from for next to nothing and then paying people to test them and sort them into matched pairs for use in his amplifiers?

It was people like Sir Clive who gave the public a taste for cheap high technology. Shame he couldn't follow through with the reliability!

Hwyl!

M.

As my Fluke has gone belly up, does anyone know of a good and cheap digital multimeter that read temperature as well complete with temp probe?

CPC do one. I got this one a while back discounted in a flyer. Described under IN0222266 £25.71 + vat but order it as code IN0222203 for £23.65 + v instead. The thermocouple is 1000mm long and everything appears to work OK. YMMV

In message , IMM writes

If you have a friend, it has to be CPC. They do a budget multimeter with a temp probe for about £30 (Maxim?)

Thanks. Is the temp probe a metal rod? I need to insert into ducts to take the temp.

Maxie, in a previous thread, I Googled, you said the cheapish CPC millimeters and temp sensors were kaka. Now you say buy them. Care to comment? Others read all this too.

Maplin dpo one for circa £19 with temp therocouple. I need a metal probe. Also BES do a similar priced one too.

If you are looking for one to check surface temperatures accurately (e.g. radiators) then a handheld band probe thermocouple will give good results.

e.g. RS Components 342-8956

There is a metal cup around the thermocouple, which is a spring loaded band. This ensures good contact and shielding from external effects.

I use one of these together with a Fluke 80TK adaptor for one of their multimeters RS 615-488

I am sure that better prices than the RS ones are available - I bought mine in the U.S. checking online sites should reveal lower prices than RS here.

It really depends on how accurate and specific you want to be at the measuring point.

.andy

To email, substitute .nospam with .gl

All the cheap ones (and some not so cheap) I've seen come with a thermocouple which is part of a semi rigid wire. But I'd say buying a metal probe as an extra shouldn't be too much of a problem given that many use the same type of thermocouple.

However, since you say you're a pro, why not by a pro temperature measuring device complete with calibration certificate?

There is quite a good booklet called "getting the most from your multimeter" by R.A. Penfold £3 odd. I think it came from Tandy when they did 'good' stuff. It is Babani press no BP239.