Author Topic: World's Worst DMM?  (Read 10609 times)

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Offline echen1024

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World's Worst DMM?
« on: October 31, 2013, 02:26:22 am »
For $1.91, is this http://www.ebay.com/itm/Digital-Multimeter-/291005261135?pt=LH_DefaultDomain_2&hash=item43c143e54f#shpCntId the world's worst multimeter? I would love to see someone zap it with 2.5k volts from an insulation tester.
I'm not saying we should kill all stupid people. I'm just saying that we should remove all product safety labels and let natural selection do its work.

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Online IanB

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Re: World's Worst DMM?
« Reply #1 on: October 31, 2013, 02:38:03 am »
I have a bunch of them. Harbor Freight Tools sells them in an appealing red color.

They are crap, of course. But they can also measure voltage accurately (the emphasis being on can).

If I wanted a DMM to give to a 5 year old to learn about batteries with, I would pick this one.
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Offline rolycat

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Re: World's Worst DMM?
« Reply #2 on: October 31, 2013, 02:48:05 am »
For $1.91, is this http://www.ebay.com/itm/Digital-Multimeter-/291005261135?pt=LH_DefaultDomain_2&hash=item43c143e54f#shpCntId the world's worst multimeter? I would love to see someone zap it with 2.5k volts from an insulation tester.

Definitely not. I have owned a DT830B for ten years or more, and it is still working and giving reasonably accurate readings.

The object to the left of this picture may qualify, though:



All three meters are connected to a power supply set to 10V, as can be seen from the Fluke and DT830B displays.

The analogue meter, however, thinks that it's just over 8V, despite having been cleaned up and adjusted.

It's Japanese, an Eagle Products TK-25, which I liberated from my Dad when I was about 10. By comparison the DT830B is a masterpiece of precision engineering.

(Edit: I have just spotted that you specified a DMM, but my first DMM was even worse in terms of build quality - it disintegrated many years ago.)


« Last Edit: October 31, 2013, 02:51:46 am by rolycat »
 

Offline jwm

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Re: World's Worst DMM?
« Reply #3 on: October 31, 2013, 02:50:10 am »
I find them useful to rip apart and get a fairly decent 3 digit voltage controlled panel meter, depending on the layout you can just chop the PCB right below the lcd after probing out the voltage and power lines. you can then directly integrate them into power supply or whatever projects.
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Offline echen1024

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Re: World's Worst DMM?
« Reply #4 on: October 31, 2013, 03:03:03 am »
AHhh yes. The Panel meter application may be a good idea.
I'm not saying we should kill all stupid people. I'm just saying that we should remove all product safety labels and let natural selection do its work.

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Offline johansen

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Re: World's Worst DMM?
« Reply #5 on: October 31, 2013, 04:51:34 am »
you can chop the circuit board right below the lcd?!
i had no clue. hmm

on the other hand, a real panel meter for 5$:
http://www.ebay.com/itm/YX-1000A-Voltmeter-Ammeter-Ohm-Multimeter-Battery-Leads-Electric-Pocket-Size-/251242439255
a meter that won't go bezerk when emi exceeds some non zero value

these don't look too bad.
http://www.ebay.com/itm/Digital-DC-AC-LCD-Voltmeter-Ammeter-Multimeter-Tester-/180766330552
too bad they need 9 v batteries.
 

Offline retiredcaps

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Re: World's Worst DMM?
« Reply #6 on: October 31, 2013, 05:42:17 am »
For $1.91, is this http://www.ebay.com/itm/Digital-Multimeter-/291005261135?pt=LH_DefaultDomain_2&hash=item43c143e54f#shpCntId the world's worst multimeter?
In Canada, there are very little auctions for multimeters on ebay.ca.  The auction above is representative of our choices.  I would get one for $1.91, but the shipping costs of $9.10 kills the deal.

Some USA sellers ship to Canada, but at $30 ish shipping charges.
 

Offline orin

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Re: World's Worst DMM?
« Reply #7 on: October 31, 2013, 06:51:47 am »
I have a bunch of them. Harbor Freight Tools sells them in an appealing red color.

They are crap, of course. But they can also measure voltage accurately (the emphasis being on can).

If I wanted a DMM to give to a 5 year old to learn about batteries with, I would pick this one.

The Harbor Freight versions will measure 10A without melting too... but best used to see if that AA cell found at the back of the bench is completely dead or not.  Don't expect better than 1% accuracy.

They eat 9V batteries if you forget to turn them off too; oh, I forgot, so do my Fluke meters.


 

Offline Stonent

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Re: World's Worst DMM?
« Reply #8 on: October 31, 2013, 08:31:46 am »
I have a bunch of them. Harbor Freight Tools sells them in an appealing red color.

They are crap, of course. But they can also measure voltage accurately (the emphasis being on can).

If I wanted a DMM to give to a 5 year old to learn about batteries with, I would pick this one.

How the hell did you do that? On the half dozen or so HF meters I've had the trimmer appears to be just for looks doing nothing.

I have red and yellow switched meters. The Red ones seem to be less glitchy though.
« Last Edit: October 31, 2013, 10:09:07 am by Stonent »
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Offline hedgewallace

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Re: World's Worst DMM?
« Reply #9 on: October 31, 2013, 09:39:47 am »
For $1.91, is this http://www.ebay.com/itm/Digital-Multimeter-/291005261135?pt=LH_DefaultDomain_2&hash=item43c143e54f#shpCntId the world's worst multimeter? I would love to see someone zap it with 2.5k volts from an insulation tester.
It says it can test AC voltage, DC voltage, DC current, resistance, transistor and diode, which is pretty much the basics. But for $1.91, it seems pretty good. I wonder what the test leads are like? Probably best not to think about them...

There seems to be heaps of these styles of meters on the market. I once owned a $10 cheapie from Jaycar (QM-1500) and the plastic coating on the test lead near the connector that plugs into the meter was stripped back after not much use. Definitely not safe.

These kind of meters are designed for people who would only use them a few times, or not very oftern.
 

Offline Stonent

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Re: World's Worst DMM?
« Reply #10 on: October 31, 2013, 10:11:15 am »
Now that I'm not at work and can see the ebay link, the model number is the same as all the Harbor Freight special clones, but the design is different.  The basic look is there but the straight transistor checker is new.
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Online wraper

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Re: World's Worst DMM?
« Reply #11 on: October 31, 2013, 10:40:04 am »

I don't understand why you hate that Rishabh so much. Leave it alone already, there was enough in the another thread.
« Last Edit: October 31, 2013, 11:21:54 am by wraper »
 

Offline Stonent

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Re: World's Worst DMM?
« Reply #12 on: October 31, 2013, 10:48:47 am »



Oops, you said DMM.
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Offline ModemHead

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Re: World's Worst DMM?
« Reply #13 on: October 31, 2013, 01:28:29 pm »
Now that I'm not at work and can see the ebay link, the model number is the same as all the Harbor Freight special clones, but the design is different.  The basic look is there but the straight transistor checker is new.
There seem to be an entire universe of variations of this "830" style meter, with quality ranging from dangerous to passable.  But they all share the same basic 7106 COB design.  I once posted somewhere that the schematic must be printed on the back of every restaurant menu in Shenzhen.

Some are well-dressed with different shapes and tool-maker brands.  Dead giveaway is the two AC voltage ranges, 200V and anywhere from 500 to 700V, depending on the optimism of the one making the label.

Pictures of the Harbor Fright variety, for those interested.
 

Offline amyk

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Re: World's Worst DMM?
« Reply #14 on: October 31, 2013, 01:51:53 pm »
They also come in kit form. I don't think any manufacturer has rated them any more than CAT II 600V.
 

Offline johansen

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Re: World's Worst DMM?
« Reply #15 on: October 31, 2013, 06:11:17 pm »
Some are well-dressed with different shapes and tool-maker brands.  Dead giveaway is the two AC voltage ranges, 200V and anywhere from 500 to 700V, depending on the optimism of the one making the label.

considering it goes to 1999.  :D

somewhere around here i might still have a photo of a not so cheap relatively unknown dmm reading -1999 volts. i then unclipped the leads, reversed them, and the meter blew up. (https://lh3.googleusercontent.com/-C-fKbwZtMAY/UnKcpjPv7tI/AAAAAAAAAi8/1mgLbpFHgDk/w867-h650-no/P1020420.JPG)

I bought 5 of those cheap dmm's (behind the dmm in the photo).. I migtht hook the one remaining functional unit up to a 6KV transformer and see how high it goes before detonation. i'll be sure and video tape it. hmm. maybe friday afternoon pacific time.
 

Offline rsjsouza

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Re: World's Worst DMM?
« Reply #16 on: October 31, 2013, 07:32:25 pm »
It is probably not the worst, but I saw this one the other day and it looked really horrid.
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Offline Dongulus

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Re: World's Worst DMM?
« Reply #17 on: October 31, 2013, 08:34:30 pm »
It is probably not the worst, but I saw this one the other day and it looked really horrid.
I own this one also from Velleman and it's pretty awful, but about what you would expect for $10 on special at Fry's. I haven't used it in a few weeks and I've just remembered that I might have forgotten to turn it off. It's probably dead by now.  :palm:
 

Offline tocsa120ls

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Re: World's Worst DMM?
« Reply #18 on: October 31, 2013, 09:23:10 pm »
They also come in kit form. I don't think any manufacturer has rated them any more than CAT II 600V.

"Teaching kit"? What are you going to teach with that? Teach underage workers how to build multimeters (and probably mp3 players/clocks/etc)?
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Offline orion242

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Re: World's Worst DMM?
« Reply #19 on: October 31, 2013, 09:23:49 pm »
I find them useful to rip apart and get a fairly decent 3 digit voltage controlled panel meter, depending on the layout you can just chop the PCB right below the lcd after probing out the voltage and power lines. you can then directly integrate them into power supply or whatever projects.

Hey now, that's a great idea!
 

Offline Lightages

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Re: World's Worst DMM?
« Reply #20 on: October 31, 2013, 09:31:01 pm »
Maybe a great idea, maybe not. If they are unreliable and show incorrect readings as has been reported, perhaps you will get an incorrect reading and fry something with the incorrect output on your power supply or whatever you trust these things to show.
 

Online IanB

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Re: World's Worst DMM?
« Reply #21 on: October 31, 2013, 09:52:19 pm »
The occasional incorrect readings seem to be caused by poor electrical contact on the rotary dial switch. If you remove the mechanical parts from the system the electronics seem to be quite reliable.
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Offline echen1024

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Re: World's Worst DMM?
« Reply #22 on: October 31, 2013, 09:53:29 pm »
It is probably not the worst, but I saw this one the other day and it looked really horrid.
I own this one also from Velleman and it's pretty awful, but about what you would expect for $10 on special at Fry's. I haven't used it in a few weeks and I've just remembered that I might have forgotten to turn it off. It's probably dead by now.  :palm:
I got one on free special at frys. It's an AND 5526 rubbish.
I'm not saying we should kill all stupid people. I'm just saying that we should remove all product safety labels and let natural selection do its work.

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Offline orion242

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Re: World's Worst DMM?
« Reply #23 on: October 31, 2013, 10:01:15 pm »
I want them nothing more than a backup volt / current meter for low voltage stuff.

Basically a temp meter to backup my ADC readings while hashing out code on a project, aka sanity check.  I'll stick to my 289s for any real measurements.
« Last Edit: October 31, 2013, 10:03:29 pm by orion242 »
 

Offline echen1024

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Re: World's Worst DMM?
« Reply #24 on: November 01, 2013, 12:16:16 am »
That is true. SO these cheap meters do have their place...
I'm not saying we should kill all stupid people. I'm just saying that we should remove all product safety labels and let natural selection do its work.

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