Multimeter?

IT depends on whether or not you've got any other use for it or ever intend to attach it to the 240V mains. It's normally safer to use one on the lowset voltage rating attached along the battery mains lead than in series with the lead, saves on expensive multimeter fuses when you open the door & the lights come on etc.

Or use a clamp meter

Take your pick if that's all you need it for. Prices range from a couple of pounds to a couple of hundred.

Ones sold specifically for cars look to me poor value.

A normal DVM can't test a car battery. Although could be used to see how much the voltage drops under load which can give an idea.

A tip is to go for one where you have to re-plug the leads to measure current - if this is done on the switch it's all too easy to blow it up.

the best type is a Fluke, but they are expensive. Maplins sell them. Maplins also sell a quite reasonable car specific (non Fluke) one for 20 quid.

I find you can still blow them up even doing that :-( The AVO ones where you couln't change the switch to volts without unplugging the lead from the current side where neat, but I gave in & gave Lem my money.

Duncan Wood brought next idea :

If that meter genuinely measures DC current with the clamp (many indicate they do, but don't), that would still not be adequate to check for the mA 's which could form the leakages (drains) as its low DC current range is 40amps. A more usal none clamp type meter with a 10amp maximum range wired in series would be more suitable, wired in series for the tests.

I have Fluke DVM I bought new many years ago. It has proved very robust and reliable. I did cost me about £90 (years ago). All I've ever had to do to it is charge the battery. Having said that I just remembered, one of the test leads has fractured near the connector end. This is not cheap as these leads (the real ones) are about £25 (I think) but then at least 10 years use (hobby level) isn't bad. ps Agree with what Dave P said, have to unplug one lead and plug it in to another socket to read current. Two ranges 10A and 300mA. One thing I like about this meter is that I trust the actual readings it gives.

Till you blow the fuse.

>

Easy... Put a 16w brake lamp bulb in series with a 10amp meter, that will limit the current to max about 1.5amp and still allow you to check for small leakage currents.

I wouldn't bother with splashing out on a Fluke for car use. My £2.99 Maplin mulitmeters are plus/minus 1.5%on current up to 200mA and all voltage is plus/minus 0.5%. More than adequate for car use. Flukes are designed for electronic design and repair work ott for car stuff. Personally I still use my Avo 8 for electronics, although it does have limitations these days, it's still nice to use. You can see a lot from a mechanical meter that is with a DMM is just jumping digits.

I fully endorse what someone said about putting a car bulb in series with the battery/meter when checking current drain. That will prevent the the DMM fuse blowing if something suddenly tries to draw lots of amps, without affecting your low current measurment.

Mark

Mark formulated the question :

Agreed.

Well, they are designed for professional use with a professional price, with professional features and calibration. I have a few Flukes and a few Maplin types and really there is not that much practical difference.

I have an old Selectest (name?) around somewhere, cheap alternative to the Mk 8. I'm idlely looking for a nice Mk8 to add to my collection at the moment. BTW AVO have only just stopped manufacturing them, due to technical problems with production. Their last selling price was around £650.

Which is where the digi meters with analogue displays are useful.

That was I, but to be fair it was an afterthought. It is what I had to do when checking my own cars static discharge. It is packed with electronics and gismos - it draws quite a large current when first turned off, until all the electronics go into sleep mode. Disturb the battery connection and they all wake back up, so it was a matter of waiting >20 minutes for it all to settle down properly before a discharge reading was valid.

I presume you are talking ham gear. I recall in the 70's I had a home built class C 20 watt power amp that was permanently across the 12 volt supply via fuses. I'd just plug in a 2m Icom when I got in the car and the power amp would fire up when it got drive from the transmitter. One hot day I noticed the power amp had problems as the RF sense relay was chattering away. Something was oscillating to itself. I checked and the heatsink was very hot and turned out is was drawing about 5 amps. Good job it had a tight filter on it's output as discovered it was oscillating out of band. Nothing got through the filter thank god.

Mark

Mark has brought this to us :

No, the electronics gizmos built into the car itself by the manufacturer.

You'll get a decent one on Ebay for about 40 quid.

It happens that Dave Plowman (News) formulated :

Yes. I saw a good one a few weeks ago at around that price, but the seller was not willing to post and it was the other end of the country.

Maplin have a cheap one for £6.99 on BOGOF at the moment. It'll do for basic autoelectrics quite easily.

That's the one I've been using for the past 8 years. I bought 4 of them when they were doing a buy one get one free. Worked out to £2.49 each and even came with a pp3 battery. Can't fault them for general use around house and garage.

Mark

A pack of fuses might be worth getting at the same time. This meter uses a

250mA 20mm fuse. GJ84F 20mm QB 250ma10 PK £1.79 In Stock

On Thu, 4 Dec 2008 00:28:27 -0000, I waved a wand and this message magically appears in front of Mark:

Thanks to all replied, I've now bought two of these multimeters, some fuses, a rechargeable PP3 battery and a PP3 recharger. Should arrive in the post next week.=20

At least I'll be able to track down the source of the drain on the battery. It's happened twice in the past week. but each time a quick

15 minute @ 20Ah recharge has quickly got the car started. The battery and alternator appears to be working just fine so I think it's either the CD player or the car alarm that's causing the drain.=20

I know the alternator is fine as there's a gauge on the dashboard that reads 14v when the engine is running.=20

--=20

Fearsome grindings.

There's little point in using a rechargeable as the battery should last a long time. You might well find the rechargeable either doesn't work properly or gives a low volts warning as many are not 9 volts nominal like a alkaline one.

When you insert the ammeter there's a good chance the fuse will blow due to the switch on surge when the battery is effectively reconnected. To save this happening use something like a single jump lead in parallel with the meter and then connect that to the battery. After a short time remove the jump lead leaving just the ammeter in circuit to measure the quiescent current draw.