Author Topic: EEVblog 121GW Multimeter Issues  (Read 195923 times)

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Offline Scottjd

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Re: EEVblog 121GW Multimeter Issues
« Reply #200 on: May 23, 2018, 03:13:34 pm »
Hi Dave, you did this video a while back with voltage. I’ve been :palm: trying to figure this out, and I think I finally figured out why my resistance testing is gettting such large differences in readings.

I haven’t had time to check the voltage and temperature change but it also didn’t jump out at me during basic testing so I’m assuming it’s probably ok.
What I have noticed is the resistor mensrment range being severely affected by the internal meter temperature. I’m going off what the internal temperature is showing on the meter.

Can you run this again in the resistance mode? Specifically the 50M resistance mode maybe with a 10M resistors? Although I’ve noticed the temperature affecting all resistance modes, the 50M ohm range seems to be the worse and most sensitive. The ambient temperature in the lab did not change more then 1C but the internal temp on the meter with backlight on went from 21.1C to 26.1C.

My Caddock 10M resistor at 0.1% tolerance is a 15ppm temp coefficient but as I mentioned the lab room temperature hardly changed at all. At internal meter reading temp it showed 10.005. By the time the meter internal temp reached 26.1C the resistor was reading 10.158. And the day my air con was off the lab was at 24.4C and the internal temp on the meter reached 28.9C and the reading was much higher at 10.356.

Despite the 10M resistor being 15ppm I also testing with Vishay that are 2ppm at 0.025% tolerances and those are affected also with all ranges I own 1, 10, 1K, 10k, 100k ohm resistors.
I will also note the 50M range seems to be the most sensitive jumping around a lot just going to push a button on the meter or waiving your hand around it.
I just want to know if this is mine only, or if you can repeate the test with the resistance mode and see if this is a common thing? And maybe the sensitivity can be adjusted in the firmware, it reminds me of your 2016 mV range video showing it being so sensitive that I believe was corrected with firmware or maybe a hardware change? If it not just mine maybe theirs a specific component this resistance mode uses that can be changed to something that has better temperature coefficiency?

The sweet spot for internal meter internal temperature seemed to be about 21.1C for all ranges.

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Offline IanB

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Re: EEVblog 121GW Multimeter Issues
« Reply #201 on: May 23, 2018, 04:15:03 pm »
From preliminary testing I find the resistance mode to have some issues.

When I short the probes to null out the lead resistance I get very variable resistance readings. Sometimes the display shows 0.000 with the leads shorted, sometimes 0.002 (I expect some 10's of mΩ -- 0.000 Ω seems unlikely). Also the display is unstable and doesn't settle. If I move my hand to the Rel button to null out the reading the display seems sensitive to the proximity of my hand. Just moving my hand near the meter with the leads shorted (with croc clips) makes the reading jump around.

The 1 mΩ precision is nice, but I think the measurement is not stable or repeatable enough for this to be useful.

Also resistance measurement shows quite odd display behavior. If I try to read a 100 Ω resistor I often see the display jump from OL to some number of MΩ, then to blank, then finally to the expected resistance reading.

Footnote: Retesting again today with shorted leads gives a reading of about 0.035 Ω, so I do not know why I kept seeing readings close to 0.000 Ω yesterday. There is somehow a lack of repeatability.
« Last Edit: May 23, 2018, 05:05:25 pm by IanB »
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Offline ChunkyPastaSauce

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Re: EEVblog 121GW Multimeter Issues
« Reply #202 on: May 23, 2018, 05:08:52 pm »
From preliminary testing I find the resistance mode to have some issues.

If I move my hand to the Rel button to null out the reading the display seems sensitive to the proximity of my hand.

Yes I'm having this as well, meter go way out of spec when touching or nearly touching buttons.

Finger just above REL button (almost touching) or lightly touching any of range-hold-rel buttons causes resistance value to change, 0.5ohm+ on mine. Same with light taps.

Also similar in the mVDC ranges.  Touching / lightly depressing the range/hold (or both) buttons causes mater to go way out of spec, 0.5mv+

v1.15
 

Offline BiOzZ

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Re: EEVblog 121GW Multimeter Issues
« Reply #203 on: May 23, 2018, 06:08:05 pm »
i took it fully apart except for the LCD and found really nothing out of place, some bodges that look fine and some flux here and there but no solder blobs or lifted components, i attached some high res photos of both sides, see if you can see anything
i also checked out under the switch and found nothing out of place

my next course of action is tracing down both signal paths and see if anything is a miss

EDIT: no attachment, too big, i placed both images here https://imgur.com/a/vHISAb5

EDIT2: I traced down what i could, PA9, PLD and PB0, none of these show a short or anything below what looks normal as referenced to agnd
i also looked at u16 and that also appears to be functional
« Last Edit: May 23, 2018, 06:36:52 pm by BiOzZ »
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Offline ChunkyPastaSauce

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Re: EEVblog 121GW Multimeter Issues
« Reply #204 on: May 23, 2018, 08:33:36 pm »
Thought I should report that the knob on mine felt way too tight, with a squeaking grind. Opened it after about a day of use and found the shim installed at Kane (from delayed batch) had been installed upside-down.


 

Offline Mag748

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In using the Diode test function, there is a discrepancy in the bar graph voltage reading and the bar graph voltage range indication.

Without any input:
In the 3V range, the bar graph indicates roughly 3 volts, and a full scale range of 5V.
In the 15V range, the bar graph indicates roughly 16V, although still displays a full scale range of 5V, which I believe should read 50V.

See images attached for your reference. Btw, I currently have FW version 1.15

Thanks,
Marcus

« Last Edit: May 23, 2018, 09:34:48 pm by Mag748 »
 

Offline IanB

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Re: EEVblog 121GW Multimeter Issues
« Reply #206 on: May 23, 2018, 09:42:59 pm »
Thought I should report that the knob on mine felt way too tight, with a squeaking grind. Opened it after about a day of use and found the shim installed at Kane (from delayed batch) had been installed upside-down.

Interesting. I wouldn't say the action on my meter feels silky smooth. I might open it up and have a look.
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Offline Scottjd

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Re: EEVblog 121GW Multimeter Issues
« Reply #207 on: May 23, 2018, 09:50:47 pm »
Thought I should report that the knob on mine felt way too tight, with a squeaking grind. Opened it after about a day of use and found the shim installed at Kane (from delayed batch) had been installed upside-down.

UODATED;
Well at least it’s not just just mine that was tight. I did finally confirm the routed are is supposed to face up, or at the PCB when re-assembled. But I think removing those three mold break points made the biggest difference. All three of them stuck up high, and without a fourth one it caused it to turn unevenly.
Scott
« Last Edit: May 24, 2018, 12:17:08 am by Scottjd »
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Offline Mickatroid

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Re: EEVblog 121GW Multimeter Issues
« Reply #208 on: May 23, 2018, 10:21:28 pm »
Thanks Dave. I suppose one of the good bits about selling meters to people like us is that many of us are prepared to have a go at some minor adjustments. If I have further problems I will try reseatting the zebra strip.

While the window is clearly very strong, as I said touching it lightly would at first cause some segments to come on. Perhaps the edges of the display were a bit jammed. Either that or I have discovered the secret touch screen option :)
 

Offline Seppy

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Re: EEVblog 121GW Multimeter Issues
« Reply #209 on: May 24, 2018, 04:35:01 am »
Due to it becoming a little disorderly and difficult to manage I have added a form on the product page to report issues with the multimeter.

https://www.eevblog.com/product/121gw/
 
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Offline Seppy

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Re: EEVblog 121GW Multimeter Issues
« Reply #210 on: May 24, 2018, 04:42:44 am »
i took it fully apart except for the LCD and found really nothing out of place, some bodges that look fine and some flux here and there but no solder blobs or lifted components, i attached some high res photos of both sides, see if you can see anything
i also checked out under the switch and found nothing out of place

my next course of action is tracing down both signal paths and see if anything is a miss

EDIT: no attachment, too big, i placed both images here https://imgur.com/a/vHISAb5

EDIT2: I traced down what i could, PA9, PLD and PB0, none of these show a short or anything below what looks normal as referenced to agnd
i also looked at u16 and that also appears to be functional

Hello,

Could I get your kickstarter details, backer number etc.

Kind Regards,
    Seppy
 

Offline BiOzZ

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Re: EEVblog 121GW Multimeter Issues
« Reply #211 on: May 24, 2018, 06:13:06 am »
I will PM you my information
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Offline ChunkyPastaSauce

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Re: EEVblog 121GW Multimeter Issues
« Reply #212 on: May 24, 2018, 03:33:53 pm »
Anyone test the 1khz LPF? On my unit, attenuation begins somewhere around 30hz (sine).

1.15
« Last Edit: May 24, 2018, 03:41:05 pm by ChunkyPastaSauce »
 

Offline Scottjd

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Re: EEVblog 121GW Multimeter Issues
« Reply #213 on: May 25, 2018, 07:38:44 am »
From preliminary testing I find the resistance mode to have some issues.

If I move my hand to the Rel button to null out the reading the display seems sensitive to the proximity of my hand.
Yes I'm having this as well, meter go way out of spec when touching or nearly touching buttons.
Finger just above REL button (almost touching) or lightly touching any of range-hold-rel buttons causes resistance value to change, 0.5ohm+ on mine. Same with light taps.

Also similar in the mVDC ranges.  Touching / lightly depressing the range/hold (or both) buttons causes mater to go way out of spec, 0.5mv+

v1.15
I can confirm this also. Since I don’t believe the meter is capable of reading mili Ohms (like most meters can’t) it probably why other meter remove the least significant digit in this range.
I have not tried relative in the mV mode yet.
Work around:  I find if you manually change it to the next range it’s a lot easier to zero out the resistance of your probes.
Scott
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Offline Scottjd

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Re: EEVblog 121GW Multimeter Issues
« Reply #214 on: May 25, 2018, 07:46:42 am »
Has anyone reported or noticed when you zero out the meter on voltage or resistance (I think all settings) and use the auto hold at the same time, the auto hold results ignore the zeroed out value when it displays the auto hold results.

Then if you turn off the Auto hold the relative triangle symbol is still displayed on the meter, but it’s not the truly zeroed out value being displayed. It’s the normal value ignoring the relative value it should be doing math with like you didn’t zero it at all. But the triangle is still displayed on the LCD. So I pushed the relative button again, instead of the triangle turning off it blinks on and off real fast and sets a new zero value.

Or, once you get the Auto hold reading without the relative value calculated into the Auto hold reading displayed, then turn off the relative set value by pressing the button again the triangle on the LCD does turn off and the Auto Hold is still displayed on the LCD. But it’s not doing any auto holding despite the LCD showing Auto hold being displayed, the meter will display the live readings with no holding at all or beep indicating it’s captured a hold.

And then also Auto hold might capture a value and beep, but if you don’t immediately remove the probe from the point being measured really fast it will display a lower value as you disconnect the probes from the source.

And it doesn’t detect small changes like mV or uV changes even when it’s set to the highest resolution using auto range or selecting a manual range. I think it’s looking for pre-set amount of change in the value it’s measuring before it will display a new hold value. I’m not sure how much difference it needs to see before it captures and display the new hold value? I think it’s between 35mV and 40mV?

Latest firmware 1.15, just recveied it today.
Scott

Has anyone been able to confirm any of these issues? To make this easier since it might not come across clear in text I’ve attached a video. Maybe someone can try the same things I do in the video and see if you can replicate this including taking a hold measument, turning off auto hold, then returning to Auto hold and reading the same source and it will not show anything (or maybe the wrong number if it changes when removing the probes).
Thanks,
Scott

https://youtu.be/l7hBJh_NMOo
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Offline ChunkyPastaSauce

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Re: EEVblog 121GW Multimeter Issues
« Reply #215 on: May 25, 2018, 09:36:30 am »
  • Has anyone reported or noticed when you zero out the meter on voltage or resistance (I think all settings) and use the auto hold at the same time, the auto hold results ignore the zeroed out value when it displays the auto hold results.
  • Then if you turn off the Auto hold the relative triangle symbol is still displayed on the meter, but it’s not the truly zeroed out value being displayed. It’s the normal value ignoring the relative value it should be doing math with like you didn’t zero it at all. But the triangle is still displayed on the LCD. So I pushed the relative button again, instead of the triangle turning off it blinks on and off real fast and sets a new zero value.
  • Or, once you get the Auto hold reading without the relative value calculated into the Auto hold reading displayed, then turn off the relative set value by pressing the button again the triangle on the LCD does turn off and the Auto Hold is still displayed on the LCD. But it’s not doing any auto holding despite the LCD showing Auto hold being displayed, the meter will display the live readings with no holding at all or beep indicating it’s captured a hold
  • And then also Auto hold might capture a value and beep, but if you don’t immediately remove the probe from the point being measured really fast it will display a lower value as you disconnect the probes from the source.
  • And it doesn’t detect small changes like mV or uV changes even when it’s set to the highest resolution using auto range or selecting a manual range. I think it’s looking for pre-set amount of change in the value it’s measuring before it will display a new hold value. I’m not sure how much difference it needs to see before it captures and display the new hold value? I think it’s between 35mV and 40mV?
1,2,3,4:yes
5: The threshold depends on the range selected I believe. Not updating until some threshold is the behavior defined in the manual though. 

I've been keeping rough track of fw issues I've come across as well. Maybe check these?

Code: [Select]
1. set max/min active, -> range button does not function

2. set max/min active, set hold, unset hold -> readings change as if max/min off, but shows max/min as on

3. set a-hold, press max/min button (note  min/max mode change is not displayed), turn off a-hold, -> max/min mode change suddenly displayed but not in min/max mode

4. set hold, press max/min button (note max/min mode change is displayed), set a-hold -> a-hold works as if max/min is off, even though max/min is displayed as active

5. In mvDC press range and immediately press REL -> REL sets before ranging completes, leaving error in offset. REL should delay until range completes

6. Short v-com, set VAC mode, set manual range other than 1000v, turn on 1ms peak, select 1000v range -> meter flashes high voltage warning symbol

7. Set a VAC mode, set a manual range, turn on 1ms peak, turn off 1 ms peak, -> meter forgets manual range set and reverts to auto range

8. Short v-com, set mVAC mode, set manual 50mv range (shows ~0mv), turn on 1ms peak, set range to 500mv-> suddenly large offset appears. Similar in Vac mode

9. Short v-com, set VAC mode, set range to 1000V, activate 1ms peak, set range to 5v -> takes over 10 seconds to switch into 5v.

10. Open v-com, set mVAC mode, set 1ms peak, switch to VAC -> mater never ranges - infinite blank

11. VAC or maVAC, set a manual range, turn on 1ms peak, turn off 1 ms peak -> meter goes to auto-range, forgetting it was in manual
 
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Offline Scottjd

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Re: EEVblog 121GW Multimeter Issues
« Reply #216 on: May 25, 2018, 10:47:38 am »
Thanks.
As for 5, I know the threshold is between 45mV and 50mV, I was going in 5mV increments. I could probably narrow is down more if I had a better mV power supply that was more accurate. It probably 50mV if I had to guess.
I need some sleep for now, but I’ve sent your tests to myself in email.
Did you check these on 1.15 or 1.17 for the things you want to me check?
I’ll check it once I wake up.

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Offline Scottjd

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Re: EEVblog 121GW Multimeter Issues
« Reply #217 on: May 25, 2018, 11:03:33 am »
I have one more for you I forgot about, but also probably related to the hold code.
In Amp if you measure current, hold the reading and pull the probes out the reading stays displayed.
In the mA/uA jack if you do the same thing when you pull the probe out, the screen goes blank. And if you had it set to a manual range it changes over to Auto range when you pull the probe with the reading on hold.
Some flukes do this from the jack detection warning, but when you put the probe back in the measurement is displayed again on the LCD. When I plugged it back in the mA/uA jack I was hoping it would display again but it didn’t. Then I realized it’s becjase it reset to Auto ranging also.
Scott
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Offline Scottjd

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Re: EEVblog 121GW Multimeter Issues
« Reply #218 on: May 25, 2018, 11:07:15 am »
My meter arrived a couple of days ago followed by an email from Kick-starter telling me it was my last chance to update my shipping details :)

Mine arrived with an immediate problem.  The screen contrast and viewing angles were weird and touching the screen even very lightly caused various segments to come on.  The packaging was largely OK, some bumps and bruises.

Anyway I gave the meter a bump on my bench (just on the top edge of the rubber surround) front and back.  Problem solved.  Not sure if the screen suffered a squish in transit or if it was pushed to hard front or back during assembly but I am thinking it was one or the other.  If you have this problem you can try giving the thing a bump.  Worked for me but, as they say, YMMV.
Mine has a weird viewing angle also, straight on is dim compared to looking up at it. But looking at a down angle it get worse, almost unreadable.

If you hold the RANGE button down when you turn it on, it will display all the LCD characters so you can check the LCD or see if some of the zebra connections are not making good contact.
Scott
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Offline bicycleguy

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Re: EEVblog 121GW Multimeter Issues
« Reply #219 on: May 25, 2018, 03:52:57 pm »
Thanks for the testing.  Haven't received mine yet.
Mine has a weird viewing angle also...

Have you tried the LCD Contrast adjustment?
 

Offline Scottjd

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Re: EEVblog 121GW Multimeter Issues
« Reply #220 on: May 25, 2018, 06:24:01 pm »
Thanks for the testing.  Haven't received mine yet.
Mine has a weird viewing angle also...

Have you tried the LCD Contrast adjustment?
Yes, contrast doesn’t change viewing angles. It just adjusts the dark and light between the displayed numbers and the background.
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Offline ChunkyPastaSauce

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Re: EEVblog 121GW Multimeter Issues
« Reply #221 on: May 25, 2018, 07:23:32 pm »
Did you check these on 1.15 or 1.17 for the things you want to me check?
I checked on both 1.15 and 1.17

In Amp if you measure current, hold the reading and pull the probes out the reading stays displayed.
In the mA/uA jack if you do the same thing when you pull the probe out, the screen goes blank. And if you had it set to a manual range it changes over to Auto range when you pull the probe with the reading on hold.
Same behavior on mine on 1.17

Mine has a weird viewing angle also, straight on is dim compared to looking up at it. But looking at a down angle it get worse, almost unreadable.
The view angle bias seems ok on mine - viewable flat on a table or looking straight on at meter (contrast does fade a little bit straight on but it's not bad). The default contrast setting on mine (4) was way too low though, I have mine set at max (7) and do wish it would go a little higher.

Noticing input jack warning doesn't function if both plugs are in the current jacks (one in A, other in uA). If in mV AC, and set 1ms peak, then input jack warning is not displayed. Similarly if one sets hold, then jack warning not displayed.   1.17
 

Offline BiOzZ

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Re: EEVblog 121GW Multimeter Issues
« Reply #222 on: May 26, 2018, 12:43:37 am »
A little update on my meter, the problem looks to be at least partly software as i cannot update the firmware, i checked out the mcu and there was some gunk over some pins as seen in attached but this appears not to be the issue, i cleaned it up and hit it with the rework station and the problem persists

when i attempt to update the firmware it looks like the micro locks up (with both 1.15 and 1.17 firmware) as some segments stay on and appear to build up and loose charge as it sits, i let it sit for an hour to no avail

at this point i have basically given up trying to repair it and hope for a replacement, i sent my details off to Seppy (i think i have, its not appearing in my sent messages)
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Offline ChunkyPastaSauce

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Re: EEVblog 121GW Multimeter Issues
« Reply #223 on: May 26, 2018, 01:35:17 am »
Bummer, but you tried

For sent messages to appear in outbox, you have to make sure "Save a copy in my outbox" is checked before sending. If you go to preferences there's a "Save a copy of each personal message in my sent items by default" option too.
 

Offline BiOzZ

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Re: EEVblog 121GW Multimeter Issues
« Reply #224 on: May 26, 2018, 01:49:33 am »
Bummer, but you tried

For sent messages to appear in outbox, you have to make sure "Save a copy in my outbox" is checked before sending. If you go to preferences there's a "Save a copy of each personal message in my sent items by default" option too.
Oh okay, thanks for the heads up ill keep that in mind
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