Author Topic: Quick GW Instek GDM-8341 bench DMM teardown / review  (Read 3111 times)

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Online bd139

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Quick GW Instek GDM-8341 bench DMM teardown / review
« on: October 13, 2017, 12:23:03 pm »
This is a relatively cheap and average spec 4.5 digit bench DMM but it has three important things for me: a dual VFD display that I can actually see in my miserable little corner bench, a cal cert and USB data logging support. I picked it up for £320 from Amazon after losing way too many Fluke 45 auctions. Figured I'd just buy a new one, but you can't get them and I can't afford a decent Keysight or Fluke bench meter new!

Notable good things:

1. Fast read speed
2. Input protection that isn't shit. Nice to see a decent quality HRC fuse and PTC in something from China.
3. Dual display (current/voltage, voltage/frequency etc).
4. VFD
5. Nice and easy to use UI.
6. Handle folds flush underneath it, not on top like some other kit.
7. Feels pretty solid.
8. No fan!
9. AC bandwidth is flat to 180KHz which is way more than the quoted 100KHz total bandwidth.
10. Relatively low burden
11. Switchable impedance on low voltage range.

CAT II rated and actually looks like it is.

Notable bad things:

1. The probes that come with it are crap! Chucked and replaced with some Pomona ones.
2. No Kelvin / 4-wire resistance measurement (I don't need this anyway really)
3. You have to manual range to use the 12A range. This confused the shit out of me for about 20 minutes.
4. Crap electrolytic capacitors. I've added a calendar entry to replace these in about 5 years :)

Design notes:

1. Lots of AD analogue switches and relays
2. Couldn't find the ADC, not that I was particularly looking for that.
3. Brains are in an Altera IC. Assume this is an FPGA, possibly with embedded core of some description.
4. It has a JTAG port by the looks.
5. USB controller is an SiLabs one. Will reverse engineer that from a host machine at some point.
6. Nice design - you can access both sides of the board once you've slid it out of the chassis.

Pictures:

Input!



Whole thing



Analogue switching



Power supply



Front



Quite happy with this  :-+
 

Offline Specmaster

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Re: Quick GW Instek GDM-8341 bench DMM teardown / review
« Reply #1 on: October 13, 2017, 01:37:41 pm »
Nice meter, HRC fuses are not uncommon on Chinese meters are they? I have them on my Iso-Tech bench meter too. i love that dual display as well, so handy

Sent from my SM-J510FN using Tapatalk

« Last Edit: October 13, 2017, 10:03:40 pm by Specmaster »
Who let Murphy in?
 

Online bd139

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Re: Quick GW Instek GDM-8341 bench DMM teardown / review
« Reply #2 on: October 13, 2017, 01:41:02 pm »
The lower end vendors tend not to bother with them. That's usually Uni-T and those awful yellow things that cost about a quid :)

Iso-Tech probably came from RS as that's one of their house brands so they have them built to a slightly better specification.
 

Offline Specmaster

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Re: Quick GW Instek GDM-8341 bench DMM teardown / review
« Reply #3 on: October 13, 2017, 04:55:09 pm »
Correct it did originate from RS, and like yours has the Bussman fuses fitted and considering what it looked like when I received it and how it looks now, combined with the price I paid, I'm well chuffed with it.

Speaking of DMM's. the Fluke 8505A arrived today from, the USA, well packed but needing lots of work I'm thinking, DC volts does seem to be reliable, not auto ranging correctly and resistance range comes up with an error message. Hoping it just needs some slight TLC, factory resetting and calibration which according to the manual can be from a computer with the right interface or directly via the front panel. Huge manual, 315 pages long to read through to find the info on how to do it etc.   :-+
Who let Murphy in?
 

Offline rsjsouza

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Re: Quick GW Instek GDM-8341 bench DMM teardown / review
« Reply #4 on: October 13, 2017, 05:44:09 pm »
Nice pictures; it is quite interesting to see GW Instek using the entire space of the enclosure - I confess I would have expected some more scantily filled product, similar to VC8145 or UT804.

It seems to me the main AD is a U303 (ADS1246) that is paired with the reference U302 (REF5025). A bit concerning that this section is so close to the beefy voltage regulators and that highway of TTL signals to the front panel...  :-//

Also, my guess is the DMM's brain is the 80MHz Cortex M4 MCU (TM4C1236) and J400 is its JTAG connector - the Altera device seems too small to hold an embedded core.
Vbe - vídeo blog eletrônico http://videos.vbeletronico.com

Oh, the "whys" of the datasheets... The information is there not to be an axiomatic truth, but instead each speck of data must be slowly inhaled while carefully performing a deep search inside oneself to find the true metaphysical sense...
 
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Offline wraper

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Re: Quick GW Instek GDM-8341 bench DMM teardown / review
« Reply #5 on: October 13, 2017, 06:01:19 pm »
4. Crap electrolytic capacitors. I've added a calendar entry to replace these in about 5 years :)
Calling capacitors crap without knowing anything about them  :palm:. Should be bottom of the barrel to be sold at Arrow and Distrelec/elfa. Every time I see someone calling them crap, that someone cannot explain why. And why would you need to replace them, there is no SMPS or heat to cause even cheap Chinese crap to fail. The only times I've seen them bulged was when general purpose series were put into SMPS or buck converter.
« Last Edit: October 13, 2017, 06:04:05 pm by wraper »
 

Offline eeviking

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Re: Quick GW Instek GDM-8341 bench DMM teardown / review
« Reply #6 on: October 13, 2017, 06:31:44 pm »
I was about to comment on that also.  :)
Jamicon is a mid-range brand out of Taiwan. I would not call them crap. They are used by a lot of reputable manufacturers.
If anyone have data to prove they are crap please share it.
 

Online bd139

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Re: Quick GW Instek GDM-8341 bench DMM teardown / review
« Reply #7 on: October 13, 2017, 06:58:39 pm »
They are definitely shit. Notorious for Sound Blaster X-Fi failures. References via Google.
 

Offline rsjsouza

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Re: Quick GW Instek GDM-8341 bench DMM teardown / review
« Reply #8 on: October 13, 2017, 07:02:28 pm »
In my experience I think Jamicon is quite alright as well. I have disassembled quite a number of products with Jamicon capacitors on them, the older being two 15+ year old Honeywell thermostats. All of the capacitors were still in quite good shape when tested with both my LCR meter and a compatible voltage leakage tester.
Vbe - vídeo blog eletrônico http://videos.vbeletronico.com

Oh, the "whys" of the datasheets... The information is there not to be an axiomatic truth, but instead each speck of data must be slowly inhaled while carefully performing a deep search inside oneself to find the true metaphysical sense...
 

Online bd139

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Re: Quick GW Instek GDM-8341 bench DMM teardown / review
« Reply #9 on: October 13, 2017, 07:16:00 pm »
One of the caps blew up in my Honeywell thermostat and sprayed electrolyte all over the membrane key switches and wrecked them! Didn’t check the vendor though at the time. Got replaced by a Honeywell remote one.

I usually only use Vishay(BC/Sprague)/Rubycon/Epcos myself.
 

Offline wraper

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Re: Quick GW Instek GDM-8341 bench DMM teardown / review
« Reply #10 on: October 13, 2017, 07:39:57 pm »
They are definitely shit. Notorious for Sound Blaster X-Fi failures. References via Google.
Way overblown to call that notorious. One out of a very few mentions of Jamicon failing. And it's a single 220uF (isn't this too low for the purpose?) LOW ESR cap working in buck converter in between of the hot heatsink (main chip) and hot linear regulators around.  Put that near to the graphics card and you have a very nice deathtrap. X-Fi has tens of other Jamicons around and not a single of them failing. I've seen 20x more faulty Nichicon (hello HN and HM series) and Nippon Chemi-con (KZG, KZJ) than Jamicon. Jamicon LOW ESR caps are not that common, to be fair. I have a few LCD monitors at my work which failed just after 2 year warranty ended and they are still going strong for 6 years after recapped with Jamicon WL.
« Last Edit: October 13, 2017, 07:44:26 pm by wraper »
 

Offline wraper

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Re: Quick GW Instek GDM-8341 bench DMM teardown / review
« Reply #11 on: October 13, 2017, 08:09:03 pm »
One of the caps blew up in my Honeywell thermostat and sprayed electrolyte all over the membrane key switches and wrecked them! Didn’t check the vendor though at the time. Got replaced by a Honeywell remote one.

I usually only use Vishay(BC/Sprague)/Rubycon/Epcos myself.


« Last Edit: October 13, 2017, 08:11:10 pm by wraper »
 

Offline nctnico

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Re: Quick GW Instek GDM-8341 bench DMM teardown / review
« Reply #12 on: October 13, 2017, 08:41:13 pm »
4. Crap electrolytic capacitors. I've added a calendar entry to replace these in about 5 years :)
Calling capacitors crap without knowing anything about them  :palm:. Should be bottom of the barrel to be sold at Arrow and Distrelec/elfa. Every time I see someone calling them crap, that someone cannot explain why. And why would you need to replace them, there is no SMPS or heat to cause even cheap Chinese crap to fail. The only times I've seen them bulged was when general purpose series were put into SMPS or buck converter.
I agree. Electrolytic capacitors in a linear PSU without a heatsource nearby can last for decades!
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline wraper

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Re: Quick GW Instek GDM-8341 bench DMM teardown / review
« Reply #13 on: October 13, 2017, 09:04:20 pm »
Nice meter, HRC fuses are not uncommon on Chinese meters are they? I gave them on my Iso-Tech bench meter too. i love that dual display as well, so handy

Sent from my SM-J510FN using Tapatalk
GW instek is not Chinese, it's a Taiwanese company and most of it's gear is made in Taiwan as well.
 

Online bd139

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Re: Quick GW Instek GDM-8341 bench DMM teardown / review
« Reply #14 on: October 13, 2017, 09:05:23 pm »
That’ll be why it has decent protection then!

I concede on the capacitors :)
 

Offline nanofrog

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Re: Quick GW Instek GDM-8341 bench DMM teardown / review
« Reply #15 on: October 14, 2017, 01:44:26 am »
Nice meter, HRC fuses are not uncommon on Chinese meters are they? I gave them on my Iso-Tech bench meter too. i love that dual display as well, so handy

Sent from my SM-J510FN using Tapatalk
GW instek is not Chinese, it's a Taiwanese company and most of it's gear is made in Taiwan as well IME.
FWIW, I picked up a couple of pieces of GW Instek gear from all the ITT surplus that hit eBay, and both were made in Taiwan. Build quality is decent IME.  :-+ Even if it wasn't wonderful, I wouldn't be disappointed given what I paid for both units.  ;)

Edit: I screwed up on COO...  :-[  :-[  :-[  :palm:
    FWIW:
    • GW Instek GDM-8251A was made in Taiwan
    • GW Instek GPC-3020 was made in Malaysia (uses analog meters vs. 7-segment displays)

    GDM-8251A


GPC-3020
« Last Edit: October 14, 2017, 08:47:41 am by nanofrog »
 

Offline Dwaine

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Re: Quick GW Instek GDM-8341 bench DMM teardown / review
« Reply #16 on: October 14, 2017, 02:23:55 am »
Ground is done Right,
 


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