Mine are still on the original batteries supplied 8 years after. Even been left on for hours on overnight a few times. They are so old now I am keeping an eye for battery leakage, but the low batt light has still not shown after all this time. I would also recommend *not* using the rechargeable.
Mark
Alex Buell brought next idea :
The meter will draw very little current from a normal PP3, so a none rechargeable should last you many years. Rechargeable one only retain their charge for a relatively short period (days, a few weeks at most), so the next time you need to use the meter you will likely find it flat.
Rechargeables are only really of use where used in something which quickly discharges a normal battery, such as models, certain types of torch etc..
On Thu, 04 Dec 2008 20:29:49 GMT, I waved a wand and this message magically appears in front of Harry Bloomfield:
Oh, bollocks. Thanks for the advice, should have known that already as my digital camera's batteries are exactly like that.
It's why sanyo/sony/etc. now sell nimhs with low self discharge.
TBH, for this application, who'd want to be trying to find the charger 2 years down the line when the meter is next used. But, yes, I'd agree with the comments so far - cheap NiCd and NiMh are not well placed in a DMM, where the operating current is so low, and the intervals of use are short duration, over long off-periods.
Just to go with the flow - a decent alkaline battery will keep you going for a year or more, better still, a lithium (although you're paying more for the battery than you are for the meter)
With low use it's the shelf life which determines when the battery is exhausted and alkaline is still better. I'm a relatively heavy user of DVMs - and rechargeables for many things - but really wouldn't bother with a rechargeable for one. Decent ones will also do an auto power down if left switched on but not used.
We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Mark" saying something like:
It's my standard practice when testing for shorts to earth in the loom.
Grimly Curmudgeon formulated the question :
In that case you might be interested in this novel piece of test equipment:-
Wire two lamps (of what ever voltage the circuit you are investigating) in series. Connect one end to the positive the other to the negative, which should then cause both lamps to light up dimly. Now add a probe connection to the middle of the two lamps. Touch the probe tip to a negative, one lamps lights up bright - touch the probe tip to a positive and the other lamp light up bright.
you can also buy a screwdriver like gadget with two leds inside which does a similar job, my one was from the MAC tools van and not very dear. your version is even more cheap and cheerful, in addition it should show up a poor connectoin better (by pulling more current), the leds don't pull enough amps and can show poorly connections as OK.
On Thu, 4 Dec 2008 00:12:29 -0000, I waved a wand and this message magically appears in front of Mark:
That one arrived early this morning and I've just used it. Appears when the engine is running it's measuring 14.49v. Which is good news. With the engine off, voltage is about 13.08v. Is that normal?
What's not so good is that I appear not to be able to measure how much current is being drawn when switched off (i.e to see if its the car alarm or the radio). How can I do that?
Alex Buell gurgled happily, sounding much like they were saying:
Sounds about right.
To find out how much draw there is on the whole system, remove one of the battery terminals and measure between the terminal itself and the lead.
To break it down into individual circuits, remove each fuse in turn and measure across the two terminals.
On 10 Dec 2008 13:49:57 GMT, I waved a wand and this message magically appears in front of Adrian:
When you say remove one of the battery terminals, do you mean, disconnect one of the leads to it, and then measure that lead and the terminal on the battery. And what setting should I be using on the multimeter?
I set the meter to the 20 symbol in the V ~~~ section when measuring the voltage, which incidentally is now 12.48v!
Alex Buell gurgled happily, sounding much like they were saying:
Yes.
Yes.
You want a current - Amps - range.
Gawd, what a useless set of ranges...
200µA, 2mA, 20mA, 200mA then nothing until 10A 200mA is probably too low for anything vaguely modern with a digital clock, remote locking, alarm, stereo memory, ECUs, etc etc.Give 200mA a try, but I'd expect it to be beyond it's capacity - in which case, try 10A - but that might not give enough detail that low.
Nope, start on the 10A range. Only if you get a reading below 0.2A should you test with the 200mA range. Significant overloads on these cheap meters is pretty much guaranteed to destroy them.
Before you start, make certain that all doors/boot are closed, and everything possible is turned off.
Harry B's tip about putting something like a 21W brake light bulb in series is well worth the effort, especially if you are not totally confident in what you are doing.
Chris
On Wed, 10 Dec 2008 14:21:50 GMT, I waved a wand and this message magically appears in front of Chris Whelan:
OK, thanks, will give that a try later today.
The battery off charge volts will be higher than actual if you measure then just after stopping the engine. Best to wait a while.
The meter needs to be switched to current - use the 10 amp range - and the red lead moved to the 10 amp socket. Then disconnect one battery lead and insert the meter between that lead and battery terminal. So they are wired in series. If you get a minus reading swap the meter connections round.
If you previously were measuring voltage and simply switched to read current on the low current range with the meter still connected you've probably blown an internal fuse in it. Exactly as was pointed out earlier in this thread.
It's a GP DVM designed for electronic use - not automotive.
If you want more 'sensible' ranges you'll need a specialist one costing many times more.
The big snag - as I said earlier - is many cars will have a switch on surge these days. So when you couple things up the initial current is much higher than the DVM can handle - especially on the low ranges. Resulting in a blown fuse at best. I've had it happen on the 10 amp range too.
"Dave Plowman (News)" gurgled happily, sounding much like they were saying:
Hmmm. Looks like you're right. I thought my own cheap'n'cheerful Draper meter had a c.1A range - but it seems to have the exact same ranges.
Easy peasy! You croc-clip one meter lead to the battery cable lug, hold the lug on the battery with one hand, then hold the other meter terminal on the battery post. Once enough time has elapsed for the surge, you move the battery cable away from the post and take the reading.
It's how I've always done it, although my background is electrical rather than automotive.
Chris
Yes - that works. I tend to use a jump lead in parallel with the meter then remove that when the surge is passed. Or the other tip to use a large lamp in series with it to limit the current. However you only usually learn this through bitter experience. ;-)
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