Author Topic: World's Worst DMM?  (Read 10558 times)

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Offline Bored@Work

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Re: World's Worst DMM?
« Reply #25 on: November 01, 2013, 06:10:03 am »
That is true. SO these cheap meters do have their place...

Yep, in the trash can.
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Offline retiredcaps

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Re: World's Worst DMM?
« Reply #26 on: November 01, 2013, 06:13:23 am »
They eat 9V batteries if you forget to turn them off too;
Most, if not all, cheap 830 meters like the three I have shown below have no auto power off.  However, I measured the current consumption of the 830s when measuring DCV using a Fluke 87. As you can see it varies quite a bit even though I'm led to believe all 830s are more or less created the same.

All figures below were recorded using min/max.  I reported the max and rounded up.

DT-830D - 1056uA

M-830B - 968 uA

DT-830B - 298uA

Fluke 75 - 276.8uA (2,000 hour battery life on 9V battery)

So if we estimate 1mA for the average 830, that should give around 400 hours of use assuming a 9V is 400mAh.

On another forum where I participate, I estimate that 80% of the people asking for help have 830 variations.  About once every two weeks, we get people with 830 meters reporting 10VDC readings on a 5V standby rail.

Invariably, the cause of this bad reading is a 9V weak battery in the 830.  However the 830 lcd, even though it has a low battery indicator, is not on.  Once we convince the user to put in a fresh battery, the 830 usually gives correct readings.

BTW, the 2 yellows ones were non functional when I received them.  I managed to "repair" them back to working order with advice/suggestions from modemhead.  I spent a lot of time doing it, but I learned a lot about.

Quote
oh, I forgot, so do my Fluke meters.
I'm curious which model handheld Fluke multimeter eats batteries.  I'm guessing the 233, 87IV/89IV/187/189, or 287/289. Most of the other models are in the 300-400 hour range.  The current 28II is 800 hours on 3 AA batteries.  Most of the modern ones have automatic power off.
 

Offline BravoV

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Re: World's Worst DMM?
« Reply #27 on: November 01, 2013, 06:36:45 am »
I own few of them although never use them anymore, starting from early version that is still using 7106 DIP package cramped into that small case and it looks horrid.  ???

@ModemHead or @retiredcaps, I think either of you should make a new thread for this popular 830 DMM, and inviting people to post their if they haven't dump it yet, I guess it will be fun to see how many variants out there.  >:D

« Last Edit: November 01, 2013, 06:49:20 am by BravoV »
 

Online Whales

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Re: World's Worst DMM?
« Reply #28 on: November 01, 2013, 06:41:41 am »
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.

Agree.  I have one at the moment, alas current measurement has been fried by testing a transistor with too high a HFE.  Indeed!

Here is another 'good' DMM:

  • Runs off a A23 12v battery.  Drains in hours of standby time
  • Has no notification when battery is low -- readings just start fluctuating like the probes are not connected properly
  • Blew the current fuse in it a few years ago, before I properly understood ohm's law.  Hence the foil :D
  • Had to severely crimp the banana sockets so they actually kept contact with the probe plugs
  • No continuity buzzer
  • Short probe leads

« Last Edit: November 01, 2013, 06:45:17 am by Whales »
 

Offline BravoV

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Re: World's Worst DMM?
« Reply #29 on: November 01, 2013, 06:47:01 am »
LOL ... love that "UNFUSED!" label there.  :-DD

Offline rsjsouza

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Re: World's Worst DMM?
« Reply #30 on: November 01, 2013, 10:48:52 am »
@ModemHead or @retiredcaps, I think either of you should make a new thread for this popular 830 DMM, and inviting people to post their if they haven't dump it yet, I guess it will be fun to see how many variants out there.  >:D
BravoV, check this other thread where people posted internal pictures of a range of 830 clones throughout the years.
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Offline amyk

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Re: World's Worst DMM?
« Reply #31 on: November 01, 2013, 10:57:37 am »
:-DD
That's the http://www.cem-instruments.com/en/pro/pro-490.html

If I remember correctly, the '830 design originated from a multimeter kit in the 80s that used the same '7106 and had the same set of ranges.

Here's one from 1996:
http://www.tequipment.net/pdf/Elenco/m-1005k.pdf
 

Offline Dark Prognosis

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Re: World's Worst DMM?
« Reply #32 on: November 01, 2013, 11:25:31 am »
The probes on the HF red one are utter shit and the black probe broke near the meter for absolutely no reason on me.  I noticed the wire inside had about 3 or 4 strands and that was it.  I don't see those as handling 10 amps of current at all so I replaced them with some 30 to 40 year old probes that are real rubber and the points will stick you and make you bleed.  I think the probes came from a VOM I found that was DOA.

As far as the uses I use it to measure 3 things...batteries (has a nice battery position), resistors, and LEDs (using the diode tester it will make them light dimly if they are good).  I would be so afraid to measure 10A of any real voltage on it.
« Last Edit: November 01, 2013, 11:27:29 am by Dark Prognosis »
 

Offline Napalm2002

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Re: World's Worst DMM?
« Reply #33 on: November 02, 2013, 01:03:15 am »
The worlds worst dmm is the one that u need and don't have
 

Offline BravoV

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Re: World's Worst DMM?
« Reply #34 on: November 02, 2013, 01:58:16 am »
@ModemHead or @retiredcaps, I think either of you should make a new thread for this popular 830 DMM, and inviting people to post their if they haven't dump it yet, I guess it will be fun to see how many variants out there.  >:D
BravoV, check this other thread where people posted internal pictures of a range of 830 clones throughout the years.
Rafael, I'm aware of that thread, its just the title is not what I'm expecting, since you're the thread creator, maybe renaming it to something like ... "Post your 830 clone and teardown" or something similar ?  >:D
« Last Edit: November 02, 2013, 02:07:52 am by BravoV »
 

Online orin

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Re: World's Worst DMM?
« Reply #35 on: November 02, 2013, 02:37:52 am »
The probes on the HF red one are utter shit and the black probe broke near the meter for absolutely no reason on me.  I noticed the wire inside had about 3 or 4 strands and that was it.  I don't see those as handling 10 amps of current at all so I replaced them with some 30 to 40 year old probes that are real rubber and the points will stick you and make you bleed.  I think the probes came from a VOM I found that was DOA.

As far as the uses I use it to measure 3 things...batteries (has a nice battery position), resistors, and LEDs (using the diode tester it will make them light dimly if they are good).  I would be so afraid to measure 10A of any real voltage on it.


I wouldn't measure 10A with pointy-ended test leads anyway unless I wanted to make sparks and potentially burn the end if one slipped.  I used something like 14 gauge stranded wire leads with banana plugs at the meter and Anderson power poles at the other end.  As for voltage, 50V DC, high side, but the meter didn't know that and I didn't tell it ;)

The power supply however (a switching 500W 50V supply), did not last - junk capacitors and a PTC thermistor that let the magic smoke out.  I fixed it, but short of an active load and some extensive testing, I'm not putting it back in service.
 

Offline ModemHead

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Re: World's Worst DMM?
« Reply #36 on: November 02, 2013, 03:25:55 am »
@ModemHead or @retiredcaps, I think either of you should make a new thread for this popular 830 DMM, and inviting people to post their if they haven't dump it yet, I guess it will be fun to see how many variants out there.
I've become a multimeter snob and I wouldn't want anyone to think I'm recommending these things.  For anything other than the scientific study of how to make stuff dirt cheap.   ;D
 

Online Whales

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Re: World's Worst DMM?
« Reply #37 on: November 02, 2013, 04:09:23 am »
FYI, I wrapped my fuse in aluminium foil because I could not find any of these official replacements:


EDIT: Woops!  Source: http://hackaday.com/2013/11/01/hackerspacing-in-europe-hack42-in-arnhem/
« Last Edit: November 02, 2013, 08:38:58 am by Whales »
 

Offline Huluvu

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Re: World's Worst DMM?
« Reply #38 on: November 02, 2013, 07:16:09 am »
 
FYI, I wrapped my fuse in aluminium foil because I could not find any of these official replacements....

:-DD :-DD :-DD :-DD :-DD :-DD

omg ......  spit all the coffee around and still laughing  :-DD
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Offline Stonent

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Re: World's Worst DMM?
« Reply #39 on: November 02, 2013, 08:38:19 am »
FYI, I wrapped my fuse in aluminium foil because I could not find any of these official replacements....

:-DD :-DD :-DD :-DD :-DD :-DD

omg ......  spit all the coffee around and still laughing  :-DD

I sent that to one of the maintenance guys at work and he got a kick out of it.
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Offline Dark Prognosis

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Re: World's Worst DMM?
« Reply #40 on: November 02, 2013, 12:45:08 pm »
The probes on the HF red one are utter shit and the black probe broke near the meter for absolutely no reason on me.  I noticed the wire inside had about 3 or 4 strands and that was it.  I don't see those as handling 10 amps of current at all so I replaced them with some 30 to 40 year old probes that are real rubber and the points will stick you and make you bleed.  I think the probes came from a VOM I found that was DOA.

As far as the uses I use it to measure 3 things...batteries (has a nice battery position), resistors, and LEDs (using the diode tester it will make them light dimly if they are good).  I would be so afraid to measure 10A of any real voltage on it.
Yeah, the pointy leads are only for jabbing in on fluxed up solder joints and was good for what I do but 10A on the 4 strands of copper wire to the leads it would just melt I think or get very hot.  The old VOM I took these off of that was buried handled 240Vac work daily so I know they can easily handle anything I do for sure.


I wouldn't measure 10A with pointy-ended test leads anyway unless I wanted to make sparks and potentially burn the end if one slipped.  I used something like 14 gauge stranded wire leads with banana plugs at the meter and Anderson power poles at the other end.  As for voltage, 50V DC, high side, but the meter didn't know that and I didn't tell it ;)

The power supply however (a switching 500W 50V supply), did not last - junk capacitors and a PTC thermistor that let the magic smoke out.  I fixed it, but short of an active load and some extensive testing, I'm not putting it back in service.
 


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