Cheap DVM's on e-bay

[NeilP]

Just seen these
DVM for £0.99



OK, only 10 Amp...but for £0.99 ($1.60) and £1.16 ($1.87) shiping from China...gotta be worth it.

And it they are not...well you have got a new set of leads

 

[grindz145]

Just seen these [img=http://cgi.ebay.co.uk/LCD-Digital-Multimeter-Voltmeter-Ammeter-Meter-OHM-DVM-/390171973976?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item5ad80fd958#ht_6254wt_907]DVM's[/img]

OK, only 10 Amp...but for £0.99 ($1.60) and £1.16 ($1.87) shiping from China...gotta be worth it.

And it they are not...well you have got a new set of leads

Thanks for the tip. I have a few of these that I picked up for $2 USD from HarborFreight when they had a sale. They're not the most accurate things in the world, and don't try to run much current through them for a while or the leads will fall apart, but seriously 2 bucks? gotta have a couple around for emergencies.

 

[Ykick]

"9V Battery is not included"

LOL...

Never have enough DVM's!

 

[NeilP]

Yes, saw no battery included...do you think we are being ripped off

I doubt accuracy will be great..but they appear exactly the same as the Silverline ones also on e-bay for £5.95..

They do not look any worse than the Sealey one I bought a few months back for £30. I ordered 3

 

[jag]

I have used exactly that kind of DMM's for 14 years. Picked up my first batch of 4 on a trip to Yunnan, China in 1998, then found them in local stores such as Princess auto. The ones in the ebay sale above is generally the cheapest version, but the exact same innards are in many more expensive store brand DMM's with slightly different enclosures.

Among the cheaper DMMs ($1-$60) I've never found that price indicates accuracy. The $1 ones on the link above are as good as the $60 "Mastercraft" ones in Canadian tire. In fact the $1 ones are more reliable. I still use the original ones from 1998, and keep getting similar ones to give for valentines gifts and the like.

 

[Hillhater]

Well, i have you there jag.. :wink:
my identical MM is now well over 20 yrs old..bought in a Spanish supermarket in the '80's for a few hundred Peseta's !!
Its still working but i recently noticed it reads a few volts high
Still, I cannot complain i guess, as i have often put near 20 A through it ( it will read up to 20A before showing the error indicator.)

 

[Ricky_nz]

I wouldn't recommend the low end meters for use on high power battery packs. They have minimal fusing and poor insulation, some would dangerous to use on either a high power battery pack or on mains.

They are perfectly fine for checking low power circuits but keep them away from high energy circuits for your own safety.
I do have one similar and its fine for low power stuff but I wouldn't use it for mains or my battery packs. The fusing isn't rated to cope with the currents our LiPo packs can deliver into a short circuit. This is the reason the fuse for the current range on a fluke meter is really expensive.

On the other hand borrowing from PC technology a
Redundant Array of Inexpensive Meters, RAIM
the multimeter equivalent of RAID could be useful :lol:

Edit:
If you do use one of these meters near your main battery a good safety measure would to tape over the current input so you cannot ever leave the probe in the wrong input. There is almost no need to measure current on your ebike in the 0 - 10A range so its sensible to prevent fireworks otherwise its not a matter of if you will make the mistake its a matter of when :lol:.

 

[John in CR]

Ricky,

We measure no load current with them. Works fine, perfectly safe. The safety risk is forgetting to put the lead back in the usual position. That's something you E guys should figure out a better design, because what I assume is intended as a safety feature ends up the opposite. How many around here haven't forgotten at least once?

 

[NeilP]

thats how I let the smoke out of my last one...trying to check 72 volt pack voltage...in the 20 Amp range...

 

[grindz145]

thats how I let the smoke out of my last one...trying to check 72 volt pack voltage...in the 20 Amp range...

I've been there... You can always replace the fuse, but that might cost more than a new DMM

 

[NeilP]

Oh no..this was way beyond a fuse

 

[NeilP]

OH....B****ks B****ks B****ks B****ks....just gone and bloody done it again.

Got a replacement for my old (one week old) meter at the store just this afternoon...then try and measure a 2 amp charge current with it...20 amp selection selected...but plugged in to the low current port....yes blew the fuse...but more than that...continuity section gives permanent 0 ohm...conductive tone...even with no loads connected....same stupid f****ng mistake in two days.... So another one shagged...and that was a £30 one as well...reckon I'll order some more of these 99p ones. being so bloody careful not to short the battery terminals together or get a high voltage flash from the LiPo's ...making sure the selector was in Amps...but not being careful enough with the bloody meter connections.
hae been using these things since a kid...so 30 years. and never a problem now in two days the same mistake twice.

 

[grindz145]

Oh no..this was way beyond a fuse

Hah. O, one of those kind 'sposions

 

[NeilP]

Well...maybe it was just the fuse...just my annoyance at being such a pratt made me replace the blown fuse with another blown one...and then get annoyed that I must have done more damage...that I did more damage....but luckily chucking the meter across the kitchen has only resulted in a cracked casing...and putting a working fuse in it now all works correctly again...still feel a bloody idiot though

 

[Jeremy Harris]

I keep a set of modified "low current" test leads for measuring low current and voltage and a separate set of "high current" leads with croc clips on that I only ever use for high current measurements. The banana plug on the positive one has a built-in 2A 20mm fuse, which avoids blowing the meter fuse. It's saved my meter fuse a few times, and given the silly price that Fluke charge for the fuse that's good thing. The only snag is that I can't remember where I got the fused banana plugs from.

Jeremy

 

[Rassy]

Ricky_nz wrote:

If you do use one of these meters near your main battery a good safety measure would to tape over the current input so you cannot ever leave the probe in the wrong input

Yep, I did that. Mild case of KFF, and melted the battery connector. It was just a 36V SLA pack. Other than having to file off the prob a bit, the meter wasn't damaged, which surprised me.

I had just started using this style of DVM after picking up several at HF on sale. My "better" radio shack DVM just has two permanent leads. First thing I did after the incident was to put tape over the third receptable, since I don't have any use for it anyway.

 

[amberwolf]

Since I have a few DMMs of various types, and two of them are basically the cheapie HF meter (though one is a different color and "brand", it's teh same inside), a few weeks ago I set one of those two to 200VDC and put a dot of superglue on the edge of the selector, preventing it from being unthinkingly turned (but not permanently set that way, as a good twist will still change it, breaking the glue). Then I set the other to 10ADC and glued that selector. Then I stuck a piece of insulation into the non-selected input probe hole, so I can't plug a probe in teh wrong place.

That leaves these two "safe" to use with my various ebike experiments, more or less. The fact that one is red and the other yellow helps, except that I can never remember without looking which is which. :lol: I tried to make it easier by thinking "High Voltage warnings are often yellow, so let's use the yellow one for DCV" and "hot stuff from high currents melting it glows red, so lets use the red one for DCA", but I somehow still never remember that without checking each time I use them.

 

[NeilP]

Might have to do the same, leave one just set for current,and as Jeremy posted earlier, fit a in line fuse in the lead, slightly less than the internal fuse...

Already go me thinking...how many poles/contacts on the rotating switch??? modify a meter so the current setting is only accessed via a momentary switch...a bit inconvenient I suppose. I was thinking a push button that only allows selection of 'Current' when the button is pushed...on release the meter returns to high voltage mode...

 

[amberwolf]

Sure...Let's say you have it hooked up across the battery terminals, then accidentally push that button, shorting full battery voltage/current thru the meter.

Better make sure that's a fast-acting fuse. :lol:

 

[NeilP]

Well yes...but at least you have to push the button, so two stupid acts rather than one. Connecting it in Current mode.

At least like that you would have to connect it AND then push the button...rather than connect it when it has been left in current mode already

 

[dak664]

Having the same probe for voltage and current is one thing that makes them cheap but if you buy more than one that isn't necessary as you will have extra probes. Put a 10 ohm resistor in the voltage probe, and fatten the current probe with tape so your hand will know the difference when your attention is elsewhere.

Not spending a lot of time adjusting the calibration pot is another thing that makes them cheap. I set mine to 5.00 using two 2.50 volt precision references in series (tedious 5 minute job) and then verify the 2.50 reading, 5 out of 6 have passed. The calibration changes if bumped hard but holds up pretty well otherwise.

 

[EDS]

There's a meter we have at work that will beep at you if you turn the dial to voltage with a lead plugged in to the current jack. It's the same sound as when you're testing continuity. Great feature. The brand is BK Test Bench.

I haven't had low current range on my meter for years - since I tried to check for voltage when installing a ceiling fan with the lead in the current jack.