Multimeter

[alan]

What is the OP likely to us his multimeter for? Checking that mains voltage is getting to his boiler Checking for a blown fuse Checking for voltage from a thermocouple Perhaps checking DC voltages on a circuit board

A basic (cheap) digital multi-meter will do all of this and probably give less ambiguous results than any of the alternatives.

Having a multi-meter and mastering the use of its functions isn't going to help much in the repair if the knowledge about the item being measured is missing.

[Martin Brown]

Depends how the question was phrased. His answer is correct but unhelpful.

There was always one student (at least) that would try to measure the source impedance of the bench mains supply by connecting an Avo across live and neutral with the range set to resistance. This tested the cutout spring device very severely and usually damaged the internals.

It is quite hard these days to get one that doesn't also do frequency. As for models well the cheapest one that Maplin or whoever has on offer for under a tenner is a reasonable bet. I have a solar powered one ten years old still going strong and incredibly small. They should all do current voltage and resistance. Buzzer continuity test is worth having as is diode test anything else a bonus unless you are into electronics.

Agreed. Particularly for a first multimeter. The other advantage is that cheap meters do not tend to go walkies like Flukes do.

[Dave Plowman (News)]

I've never managed to damage one by probing volts when in resistance mode

- although I suppose you might if the volts are high enough.

Half decent ones have a fuse to prevent damage if you probe volts while set to current. On a Fluke (and maybe others) these fuses can cost more than a cheap meter. ;-)

[Dave Plowman (News)]

Think that's a misleading statement. A high input impedance is a virtue - in the days of analogue meters you had to pay dearly for the privilege, in the form of a valve voltmeter.

It's very easy to change a high impedance one into a low impedance type by adding resistance across the input. The other way round, not.

But in any case voltages measured with no load are pointless. Especially on cars. To get a true reading the circuit should be under load.

[Dave Plowman (News)]

For not much more money you can get digital meters with an additional scale which mimics a needle display.

[Dave Plowman (News)]

Even if setup to measure current? Now that would be useful...

[The Medway Handyman]

> Owain

That's made me think. All I really need is voltage & continuity.

Typical application, client removes loop in rose, joins all reds, all blacks, loses sleeve on switch live. Quite common.

I find it a right PITA trying to hold two 'probes' and the DMM so I can see it. You need three hands!

Something like that where the results are displayed on one of the 'probes' would be much easier.

[The Medway Handyman]

Oddly they are much more expensive than a cheap DMM?

> Owain

[PeterC]

>>> Owain

When I first got a MM I made up a 'probe' from a suitable plug, an insulated pin clip and about 20' or so of nice flexible wire. It's greta for clipping to a terminal and then I can wander off looking for t'other end of the connection. Very handy in France in a house with a mixture of French and English cabling and circuitry.

[Moonraker]

Ah when I was a sprog all that were available were Avos, very reliable though needing regular calibration, we were thoroughly taught how to use them. Oh yes there were Megggers as well, but hardly multimeters!

[PeterC]

Bad case of DTs?

Perhaps he'd worked for Microsoft.

[Bob Eager]

and a needle.

[NT]

Fuses arent very effective at protecting analogue meters on a low current range. Most folks buy digital now though.

NT

[NT]

The only ones I've seen have such low resolution pointer displays as to be useless, and the main advantages of analogue meters are all absent. Ie the ability to follow a varying signal, and the ability to estimate heavy overcurrent by pointer speed.

NT

[Owain]

Most of them also buzz on voltage or continuity. So you can attach to the circuit with croc clip probes and go away and flick MCBs until the buzz stops if you need to find the circuit. Etc.

Owain

[Adrian C]

The basic questions

1) Is there voltage there? 2) Is my device drawing current? 3) Is there resistance or continuity between two circuit points?

Require different hookup of a meter. Best get an understanding of concepts of a circuit, ohm's law, and metric prefixes - Kilo, Milli, Mega ... etc

One of the basic mistakes beginners do is try to find measurements for silly questions like "Is there current ACROSS these two points". The probable second "Is there resistance in this POWERED circuit?". The meter normally responds by popping a fuse or, worse, bursting into flames.

Cheap as chips digital meters are fine for a start, but pay respect with live electricity - it bites mucho.

[Dave Plowman (News)]

You can see that on a low resolution display. Only thing you can't do is read a figure accurately. And autoranging would get round the second part.

[geoff]

In message , charles writes

The demon drink, eh ?

[Dave Plowman (News)]

That's probably because they don't use a clever fuse like Fluke do. Not invented when the AVO8 was king.

Quite. Have you seen the price of a new AVO8?

[Dave Plowman (News)]

Quite. What's needed is understanding the basics of electrical theory. Using a DVM then becomes intuitive for the basic tasks. Doing things the other way round is pointless.