Quick GW Instek GDM-8341 bench DMM teardown / review

[bd139]

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 

[Specmaster]

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

[bd139]

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.

[Specmaster]

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.   

[rsjsouza]

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.

[wraper]

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  . 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.

[eeviking]

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.

[bd139]

They are definitely shit. Notorious for Sound Blaster X-Fi failures. References via Google.

[rsjsouza]

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.

[bd139]

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.

[wraper]

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.

[wraper]

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.

[nctnico]

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  . 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!

[wraper]

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.

[bd139]

That’ll be why it has decent protection then!

I concede on the capacitors

[nanofrog]

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...       

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

[Dwaine]

Ground is done Right,

[Inflex]

Apologies for reviving an old thread.

What's the continuity and diode mode speed like?  I'm looking to purchase this meter but if the continuity speed is slow (ie, more than "near instant") it might not be viable.

[bd139]

Couldn’t answer that for you. I don’t own it any more.

In fact I’d recommend avoiding the meter at this point. It’s nearly impossible to find someone who can calibrate it.

[Inflex]

Hello @BD139,
 
  Thanks for the quick reply.  More and more looking like it'll be back to the VC8145C for the job it'll be used for ( board repairs, not precision work ).

[HKJ]

Hello @BD139,
 
  Thanks for the quick reply.  More and more looking like it'll be back to the VC8145C for the job it'll be used for ( board repairs, not precision work ).

You can compare a couple of bench meters here: https://lygte-info.dk/info/DMMReviews.html
Click on the "Type" column for sorting.

[bd139]

Just a few! 

I wouldn’t bother with a bench DMM now. Invest in a Fluke 87V or Brymen BM867s and job done.

[Inflex]

Just a few! 

I wouldn’t bother with a bench DMM now. Invest in a Fluke 87V or Brymen BM867s and job done.

I genuinely prefer bench meters.  Gone through enough hand-held units and still have a few as a fallback, but bench meters stay out of my way, don't turn off, have decent data connectivity and I can program them to switch modes from my software.

[Inflex]

You can compare a couple of bench meters here: https://lygte-info.dk/info/DMMReviews.html
Click on the "Type" column for sorting.

Unfortunately there's no spec on how quickly the continuity mode works.  Some meters, you encounter a short (say, below 20R) and they'll near instantly beep; others, seem to go out for a cup of coffee, mull over the crossword in the latest newspaper and eventually get back to you with a "Oh yes, that might be a short".

VC8145, BSIDE ADM20, B&K 390A seem to be fast enough but it would appear some of the better meters seem to go slower than anticipated with continuity.

[bd139]

Just a few! 

I wouldn’t bother with a bench DMM now. Invest in a Fluke 87V or Brymen BM867s and job done.

I genuinely prefer bench meters.  Gone through enough hand-held units and still have a few as a fallback, but bench meters stay out of my way, don't turn off, have decent data connectivity and I can program them to switch modes from my software.

HP 34401A then