Author Topic: EEVBlog 121GW Multimeter Firmware Details  (Read 70813 times)

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Offline Lion_Tamer

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #150 on: November 25, 2018, 10:09:45 pm »
I have just tested my meter on the capacitance mode to see what sort of drift it has with results as below:

Set-up = The meter was placed in front of me between my keyboard and 2 monitors, probes were plugged in and clipped in to the holder on the back with nothing else connected and the excess lead laying on the bench. Blue tooth and logging was turned off. I left the meter in auto range mode on capacitance mode. Test length was 30 minutes each time.

Test 1:
Firmware Version 1.51
Available Resolution 10nF
Starting value 0.00nF
End value 0.00nF
Comment: At no point in the test did I see the meter value change.

Test 2:
Firmware Version 1.57
Available Resolution 1nF
Starting value 0.000nF
End value 0.002nF
Comment: The meter drifted up to 1pF after about 5 minutes and 2pF after 10 minutes, at one point during the test I did see 3pF on the display but it only lasted a couple of minutes.

I also tried touching but not pressing the buttons and leads during both tests with no noticeable changes to the displayed value.

Meter Serial No:180701854

I may have to look and see if I have any low value caps to test with when I can get a chance to sort my workbench out after recent building work.

Jem
 

Offline CDaniel

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #151 on: November 25, 2018, 11:01:51 pm »
For capacitance there is not a zero offset calibration in the manual , anyway with or without the leads connected is showing 0.000
Interesting ...
 

Offline lowimpedance

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #152 on: November 26, 2018, 01:44:56 am »
*********************************************************************************************************
Jan 8th 2019
EDIT : Just for clarity of my posts and further down in relation to the problem found with the capacitance measurement. 

Below was in response to a previous members post relating to a bug (as noted above, and yes this is not the correct thread for this stuff but anyway..).
A number of posts by another member were removed by them which generally makes the thread seem disjointed with my responses.
But as the detail of my posts are still of interest I will leave them here.
I did ask in the other thread when the discussion moved there to move the posts from here but that did not happen and that time window has long passed.

*********************************************************************************************************
Okay I updated my kickstarter meter (1st batch) to firmware 1.57. And tested some lowish value capacitors. All connected to the meter via short leads and croc. clips.
The Meter was in Auto ranging mode and gave quick measurements on the three capacitor values when connected.

first value
 100pF silver mica.
 Initial connection showed 0.100 nF +/- 1pF -2 pF. With no capacitor connected the meter reads 0.000 nF
Repeated disconnect and reconnect gave same result. Leaving the cap connected and then turning meter OFF then ON from the RH OFF position did not affect the measurement.
Now using the LH OFF position introduced errors into the measurement, which then also persisted when also using the RH OFF then back to ON. A 100 pF with a variable reading
around 30 pF (not consistent).  :-\
Also cycling through the modes on that switch position did not restore correct measurement.

 1 nF polystyrene
 Initial connection showed 0.990 nF
Repeated connection gave the same result. Leaving the cap connected and then turning meter OFF then ON from the RH and the LH OFF position did not affect the measurement.

10 nF silver mica (a L&N standard cap !)
 Initial connection showed 10.110 nF. Cycling through the modes back to capacitance again now gave a reading of 10.040 nF. (This value corresponded to my Fluke 87V after I REL the 0.26 nf Offset out  :P.)
Repeated connection gave the same result. Leaving the cap connected and then turning meter OFF then ON from the RH and the LH OFF position did not affect the measurement.

Last test was to 'pad' the input capacitance with the 1 nF and REL it out then connect the 100 pF and repeat that a number of times.
The measured value was 0.100 nF and was the same each time it was re connected.

No drift measurement done
*******************************************************

NOTE :When I went to the firmware download page I noted a message above the firmware list saying quote:
"NOTE: This version has a change that will not function correctly with the app in capacitance range. An update to the app will be released soon."

Its not clear if this refers to the current firmware on the list with the DMM and the logging app or just the capacitance mode on the meter itself  :-//.
Or this message has been there for many firmware revisions !, as I only just updated from 1.17 its been a while since I looked at the firmware page.
« Last Edit: January 10, 2019, 12:48:34 pm by lowimpedance »
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Offline lowimpedance

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #153 on: November 26, 2018, 02:29:14 am »
 Yeah , not sure what to make of the initial success with using the RH OFF only, as it generally went (and stayed) pear shaped after using the LH OFF.
Will try to repeat after the meter has been off for some time.
My testing was with a pair of DIY short leads so not much to twist so thats why I used the 1 nF  to get of the measurement 'floor' !. Seemed to give good results after the REL.
 I had quite a lot of issues directly attributable to the sloppy switch which I resolved with similar shimming before the official shim was released.
Still not convinced this switch design is issue free yet.


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Offline lowimpedance

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #154 on: November 26, 2018, 05:37:11 am »
 Re test of 100 pF after more than an hour turned off. Result was a correct reading of 0.100 nF when connecting / remove and re connect to the croc. clips.
Next leaving connected and turning OFF/ON from both directions initially gave correct reading but a short time later the reading started to display approx 82 pF instead.
I then cycled through the modes on that switch position and then re measured the 100 pF with the result now down around 25 pF or so as previously tested.
So a sort of repeatable result.
 Noted that the larger capacitance measures start a bit higher as well and then drop a small amount and could correlate to the same amount observed with the 100 pF. Needs further testing.

At this stage I have no plans to remove the switch, which considering the amount of usage I have given it would probably not show to much wear.
They did appear to be quite clean at the time I had the switch out, (nice gold plating).
However I will keep this in mind for when I do feel motivated to get in there again
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Offline Terry01

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #155 on: November 26, 2018, 08:38:33 am »
Quote
... gave correct reading but a short time later the reading started to display approx 82 pF instead.

If you watch that short clip I made, do you feel I was not waiting long enough?

About three hours now at 27C.  The 121GW  proto still has not budged off 16pF.   Looks like 27C was too low of a setpoint.  The camera, meter and fan are more than what all that insulation will carry away. 

The one problem I have noticed is how far off the meters internal temperature is.  About 10C low.  It may have always been this far off or maybe they changed the thermistor.   The schematics are the same.   There appears to be no way to align it outside of changing R38.  May be nice to have a way to trim it as part of the alignment.

I got a 121GW new a few days ago with v1,54 firmware installed and noticed the internal temp is around 2.5C higher than the internal temp in my U1273 when the temp is around 15C. As the temp gets nearer 20C it wanders to being around 3C higher. The 121GW also wanders quite a bit more on start up where as the U1273 is a lot steadier. The 121GW changes from anywhere around .5C to 1C in the first minute after start up.

« Last Edit: November 26, 2018, 08:43:46 am by Terry01 »
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Offline lowimpedance

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #156 on: November 26, 2018, 09:15:34 am »
@Joe, I have not watched the video yet but I will and comment then.
When measuring the 100 pf after the unusual drift to the lower value I did not observe a further drift of more than a few LSD. I will check for drift tomorrow with the 100 of from the first start.
I will also pay attention to the measured temperature compared to other meters for any differences from the lab temperature.
« Last Edit: November 26, 2018, 09:18:16 am by lowimpedance »
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Offline lowimpedance

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #157 on: November 26, 2018, 11:06:54 pm »
 Okay this morning I turned the 121 on an noted an initial reading of 0.012 nF with no connected cap. Which is what I had observed previously.
Next I connected the 100 pF and the reading was 0.111 pF then over the next 10 minutes that slowly drifted down to 0.109 pF as the 121 warmed up !. No further significant change observed.
The meter was kept in a temp. controlled lab overnight and is sitting at 21.40 deg. as recorded on a Guildline 9540 PRT temp. meter. The 121 secondary temp. reading was also 21.4 deg.
 Now the interesting bit, with the 100 pF still connected I cycled through the modes on that switch position and now the 100 pF measured as 25 pF and would stay at the value when either
turning on or off or disconnecting or reconnecting the cap.
Leaving the unit off for a short time and then turning back on shows the measured value to be increasing back to the correct value !!. just like something has a residual charge being slowly bled away.
 At re-switch on it showed approx. 68 p and after 10 or so minutes was up to 93 p, and now at 103 pF after 20 plus minutes...... :-DD
Interestingly the display will show 0.000 nF with no connection, when the 121 starts to give wrong measurements.  (mode cycling).
Perhaps the firmware hides all negative readings and just gives all 0  :P.

@Joe , Looking at your video I would say the behaviour was consistent with mine when measuring a 1 nF cap although I did note a change from the initial value down from 1.016 n to 0.977 nF after mode cycling.

OT:, and yay post 1000 !..........only took 7 years  :-DD
« Last Edit: November 26, 2018, 11:54:27 pm by lowimpedance »
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Offline CDaniel

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #158 on: November 26, 2018, 11:58:01 pm »
If you have some initial reading when you cycle through modes will clear that ... in my case anyway .
There has to be some kind of automatic zeroing when switching to capacitance , otherwise there is no way to read 0.000nF with or wihout leads ( long , short or how you want ) . If you put the probes close but not twisted together the capacitance is at least 10pF .

So if you leave something connected at start-up will screw-up the auto calibration ... my theory .

Maybe this feature  is not well design and is responsible for what we observe . Why some meters don't have the issue is interesting , the external electromagnetic fields may play a role .
« Last Edit: November 27, 2018, 12:07:21 am by CDaniel »
 

Offline lowimpedance

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #159 on: November 27, 2018, 12:04:17 am »
Additional info:
 I cycled the modes on the switch position to get the wrong capacitance reading of 24 pF with a 100 pF silver mica capacitor connected, then I left the meter running and waited.
The meter did auto power off but on restarting the meter using a key press the reading was correct at 109 pF. The time that passed was at least 30 minutes.
So all I did was to return after a half hour and turn the mater back on to now show the correct value.

Mode cycling will fully cause the issue to present itself each and every time on my meter.
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Offline Lion_Tamer

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #160 on: November 27, 2018, 12:25:07 am »
I had a dig through my parts bin and found a 27pF ceramic capacitor to try drift testing with tonight - so far I have only tried V1.57

Using a peak LCR meter the cap measured at 22.5pF

This time I also turned on logging (Results below). The maximum value that I obtained was 21pF with a minimum of 0.15pF in a non temperature controlled environment (probably only changed by a couple of degrees).

After the drift test I tried turning the meter off then back to capacitance mode several times, initially the read value would drop by a couple of pF before suddenly dropping to zero after which it did not seem to matter what I did with the meter it would not read any pF value for about 30 minutes.

Jem
 

Offline lowimpedance

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #161 on: November 27, 2018, 01:32:09 am »
 I would say that behaviour is consistent with my meter. Could you also cycle through the modes on that switch position, (from capacitance  through ohms etc and back to capacitance), when starting with 21 pF.
What reading do you get after the mode cycle ?.
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Offline Terry01

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #162 on: November 27, 2018, 12:30:04 pm »
Hi Joe can I ask a very beginner question? Do you use the 2 x BNC to 4mm connectors to give a more stable reading of the cap under test and eliminate the capacitance that would be in the leads if you used them? Sorry for the dumb question but I would like to learn these things.  ???
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Offline Terry01

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #163 on: November 27, 2018, 03:03:11 pm »
Hi Joe can I ask a very beginner question? Do you use the 2 x BNC to 4mm connectors to give a more stable reading of the cap under test and eliminate the capacitance that would be in the leads if you used them? Sorry for the dumb question but I would like to learn these things.  ???
I started out with an old VTVM and later a Radio Shack analog meter.   

The leads can interact with themselves and their surrounding environment.   Looking at extreme values of anything makes the setup more critical.  In short, I would say stability is a good word.

Cool...thanks for the explanation.  :)
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Offline chronos42

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #164 on: November 27, 2018, 03:42:09 pm »
Good to see that I am finally not the only one with this odd problem...

And to joeqsmith: You had every reason to ask, i did not belive it too after I saw this behaviour the first time.

 

Offline lowimpedance

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #165 on: November 29, 2018, 05:00:55 am »
If you have a way to take some high resolution pictures of the switch contacts, it would be interesting to see how they are wearing.   
I actually had an occasion to have the switch out and not having any means to take a high res pic. I tried to get the best with the crummy camera I had to hand. See image attached.
Looking as close as I could with a magnifying glass I cannot see any notable wear on my meter. But then again it has not reached 50000 rotations  :D.
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Offline nonentity

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #166 on: November 29, 2018, 08:04:36 am »
I'm wondering if the administrator has considered combining some of these threads with the issues section.  It started out with discussions about firmware metadata, but looks like it has morphed into issues. 
Topics I would expect to see in firmware details discussions would be:

Design Requirements, i.e., what things is it supposed to do and will those things be tested?
Configuration Management/Control, i.e., what really is in V 1.57 and what should go into 1.58 and why?
Test methods and results, i.e., how is it going to be tested? Was it tested? And where are the reports?
Documentation
Quality Control
 
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Offline lowimpedance

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #167 on: November 30, 2018, 05:41:22 am »
@Joe
 I used the Mantis at work to inspect the switch pattern and I could not determine if the black material was metallic in nature , quite possible there is some.
The reason is after a good clean I could see (using a 10X mag. eye loupe) that there was notable wear on some of the dimples on the switch fingers in the rotor.
Ie: the dimples that were a bit higher and thus had more pressure on them had worn down through the gold plate to the copper underneath. And this could well be the source of the black material on the PCB.
The PCB switch pattern however looked perfectly fine with minimal wear after cleaning.
I will try to get hold of a USB microscope to take some pictures (Monday!).
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Offline CDaniel

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #168 on: December 02, 2018, 08:19:26 pm »
My meter  180701918 from Welectron






« Last Edit: December 02, 2018, 08:23:00 pm by CDaniel »
 

Offline Terry01

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #169 on: December 02, 2018, 08:42:20 pm »
I got mine around a week ago from Welectron too but it's only been used a few times since so the contacts will still probably be "as new" so hardly worth showing just yet. I'll wait till I've had it for 6 months or so then i'll open it up and post a few photos.
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Online gnavigator1007

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #170 on: December 02, 2018, 09:33:41 pm »
I got mine around a week ago from Welectron too but it's only been used a few times since so the contacts will still probably be "as new" so hardly worth showing just yet. I'll wait till I've had it for 6 months or so then i'll open it up and post a few photos.

Might be worth it to open it now and grab some pics to compare down the road. Obviously, should still look new with no wear, but you don't really know without a peek.
 

Offline Terry01

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #171 on: December 02, 2018, 11:15:36 pm »
I got mine around a week ago from Welectron too but it's only been used a few times since so the contacts will still probably be "as new" so hardly worth showing just yet. I'll wait till I've had it for 6 months or so then i'll open it up and post a few photos.

Might be worth it to open it now and grab some pics to compare down the road. Obviously, should still look new with no wear, but you don't really know without a peek.

Very true, I never thought of it like that. I'll open it up when I get up in the morning and post a couple of the pics I take.
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Offline CDaniel

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #172 on: December 03, 2018, 12:44:18 am »
My meter  180701918 from Welectron
So they went from all single dimples to double dimples and now they are back to single dimples??  It looks like the dimples are showing some wear on yours as well as the pads.  Are we starting to see some copper exposed on the pads?

That is "black dirt " , after a wipe with alcohol looks like new , no sign of wear on pads .
But I didn't work with it much , as we know has "some" bugs and I don't like this ...
I'm more worried about this issues ...


I would like to see a comparation with other multimeters using HY3131 , Keysight U1282A for example ...
« Last Edit: December 03, 2018, 12:59:41 am by CDaniel »
 

Offline Terry01

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #173 on: December 03, 2018, 01:11:42 am »
My meter  180701918 from Welectron
So they went from all single dimples to double dimples and now they are back to single dimples??  It looks like the dimples are showing some wear on yours as well as the pads.  Are we starting to see some copper exposed on the pads?

That is "black dirt " , after a wipe with alcohol looks like new , no sign of wear on pads .
But I didn't work with it much , as we know has "some" bugs and I don't like this ...
I'm more worried about this issues ...


I would like to see a comparation with other multimeters using HY3131 , Keysight U1282A for example ...

I have Keysight U1273A...does that have HY3131?
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Offline lowimpedance

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #174 on: December 03, 2018, 01:20:13 am »
I have taken some pictures of my 121 ontacts using a USB microscope and attached for your ref.
note its quite hard with the gear I had to hand to get the best contrast, so may not be the absolute best representation.
The wear appears to be uniform across most of the dimples. The cotton tip I used for cleaning only shows the 'black stuff' and no discernible metallic debris.
The PCB traces look good with no obvious 'wear track' forming.
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