Author Topic: EEVBlog 121GW Multimeter Firmware Details  (Read 70897 times)

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Offline Terry01

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #125 on: November 21, 2018, 10:58:40 am »
I know this is a tiny bit off topic for this particular thread but for those who are interested in V 1.54 firmware, I just did a quick check of all the modes and ranges on my new 121GW that came with the V 1,54 firmware installed from Welectron yesterday.

I tested it alongside 6 other meters doing a general function test, i checked caps, resistors, diodes, voltages and currents of all different values and sizes and it was very close in every test same as the rest of the meters were. I didn't expect them to match exact to the last digit.
I didn't notice it to be particularly slow either or anything like that in any particular mode.
The only thing I didn't test was the mvA/VA feature as I don't know exactly how it works to test it. I'll learn that soon enough though.
To sum up i am happy with the meter so far in how it performs.

Hope this is of interest to someone.
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Offline thaistatos

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #126 on: November 21, 2018, 11:53:45 am »
is there an improvement of the slow reading of resistance?
 

Offline rattnallen

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #127 on: November 21, 2018, 02:19:25 pm »
 

Offline Terry01

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #128 on: November 21, 2018, 02:26:51 pm »
Firmware version 1.57 at https://www.eevblog.com/product/121gw/

I saw that but there was no V 1.54 which I thought was a bit strange. I'll wait and see as I am happy with it just now.
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Offline exe

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #129 on: November 21, 2018, 03:33:52 pm »
And I hadn't even heard of ChibiOS. Can you share what you have so far?

Uhm, not much, just a proof of concept for another project: https://github.com/kopchik/psu_firmware/blob/master/main.cpp . I use ChibiOS because:

1) reasonably simple API
2) Supports Linux (and any other sensible OS)
3) Provides threads and queue support. This is a must for me for any async UI development.
4) Sources are written by humans, not a typical autogenerated rubbish :)
5) I don't care about power consumption, if a DMM gonna work 50hrs from batteries instead of 600h it's still fine provided firmware is better than the stock one.


PS I think I'll finish my other projects first before jumping on this train. Don't want to spread too much.
 

Offline Dirk C.

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #130 on: November 21, 2018, 05:18:33 pm »
is there an improvement of the slow reading of resistance?

In Auto Mode it is not fine, slow.
In manual mode the measurements are very fast.

Version 1.57

Dirk
 
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Offline chronos42

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #131 on: November 23, 2018, 05:39:20 pm »
Hi,

there is indeed an extra digit.
I have made some test and found this:

In the higher ranges the meter is still slow but accurate and has a higher resolution.

DER EE 5000 as reference meter, 100nF (MKT type capacitor) @1khz : 113.68nF

Agilent 1252B : 114.2nF
Brymen BM869S : 114,4nF
UNI-T UT201E (cheap clamp meter) :114.4nF
121GW: 0.1129µF


So far so good, all meters are doing a good job.

Next with a 220pF ceramic NP0 capacitor:

DER EE 5000 as reference meter, 220pF@10khz : 238.3pF

Agilent 1252B : 0.234nF
Brymen BM869S : 0.24nF
UNI-T UT201E (cheap clamp meter) : 0.240nF
121GW: 0.165nF

All meters are spot on, except of the 121GW which is way off and not even close to 220pF. It seems that the low capacitance range now is messed up. Can sombody reproduce this issue?
« Last Edit: November 23, 2018, 06:41:18 pm by chronos42 »
 

Offline exe

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #132 on: November 23, 2018, 07:02:35 pm »
There is a separate thread for reporting bugs, and another one for general discussion. It's unlikely to get much support in this thread.
 

Online CDaniel

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #133 on: November 23, 2018, 10:21:47 pm »
Sub 1nF readings drift and are affected by noise , if you touch the probes , etc , this must be investigated further . I don't think it is normal ... another issue maybe . If I used REL just before the measurement and I didn't touch anything was accurate for low capacitance  ... but needs more testing .

If you touch only the red probe tip you can get a reading of a few nF , this it is not scientific but an indication that is not very ok .
« Last Edit: November 23, 2018, 11:51:20 pm by CDaniel »
 

Offline chronos42

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #134 on: November 24, 2018, 07:44:17 am »


What versions of firmware were you testing?  What were the values reported for that version?   How long did you allow the 121 to settle?

Hi,

sorry, I forgot the version information.
It is 1.57.
« Last Edit: November 24, 2018, 08:10:28 am by chronos42 »
 

Offline chronos42

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #135 on: November 24, 2018, 08:09:46 am »
Hi joeqsmith,

I can repeat this and get the same result every time.

Now with a 0.39 nF NP0.

DE EE 5000: 392.6pF @ 10kHz

121GW (Firmware 1.57) : 0.316nF.
The meter is about 80pF too low in the lowest range, capacitors lower than 81pF are shown as 0.000.

Unfortunately I don't know from which Firmware on the problem started, maybe I have lost a small part of the calibration. The other ranges are spot on as mentiond before.
Seems that I am the only one whith this problem?
« Last Edit: November 24, 2018, 03:08:33 pm by chronos42 »
 

Offline chronos42

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #136 on: November 24, 2018, 11:13:43 am »
Hi,

I did some more tests and found that this seems to be a problem only for my 121GW, it has nothing to do with the firmware.
My meter reads about 80pF too low in the lowest capacity range. It does this also with firmware 1.26 and the original calibration data, saved on the SD card.

Update:
After I have played with different firmware versions, I went back to 1.57, restored the original cal data again and made a new offset correction for all current ranges, because there was a large offset since firmware 1.5X.

And now the low capacity range works, it is only off for some pF.

WHAT???  :-//

This is really strange, I have no idea what happend, something in the calibration seems to be mixed up by some firmwareupdate in the past.
« Last Edit: November 24, 2018, 11:43:18 am by chronos42 »
 

Online CDaniel

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #137 on: November 24, 2018, 12:56:37 pm »
It is not working reliable for small capacitors , sometimes a remanent value of 20-60 pF remain on display . Disapear only if I switch to resistance and back .
I assume this can be negative as well but you can't see it ( below 0 ) and substracts from real value , sometimes I can get -80pF lower reading like in your case .
« Last Edit: November 24, 2018, 01:01:10 pm by CDaniel »
 

Offline chronos42

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #138 on: November 24, 2018, 01:59:03 pm »
Hi CDaniel,

thanks for the answer, so it seems I am not the only one with this issue.

Update:

I could repeat this behavior.
100pF capacitor:

I switched on the meter, it showed 0.100 nF, first time spot on!
Switching off and on again, now it showed 0.082nF.
Switched to Ohms an back to capactity: Now it showed 0.021nF, after switching off and on again sometimes 0.014nF, sometimes 0.021nF, but never again 0.100nF.

Does the 121GW only one time per day show the correct value in the pF range?... :-DD
« Last Edit: November 24, 2018, 04:43:22 pm by chronos42 »
 

Online CDaniel

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #139 on: November 24, 2018, 06:30:38 pm »
If I just put the fingers on buttons the value is changing by ~60pF ... so about what precision we are talking about ?  :-\
Measuring a precision capacitor the displayed value is drifting in time (10min) by at least 50pF .
This is again a problem with AC noise , like it was in resistance mode ( now resolved )

The behaviour can be somewhat different because everyone's lab is different , probably even the spot where it sits counts ...
 

Online CDaniel

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #140 on: November 24, 2018, 07:58:51 pm »
No , I don't touch or move anything and it drifts .
You don't use the probes , that is a very big difference .

The problem is not how you should measure for maximum precision pF capacitance , we know and we have RLC bridges for this , but if the meter is comparable with other good multimeters ... who we presume should not drift much and you can use the probes just in case you need to measure something accurate . This is a portable handheld multimeter after all , not to sit in the best conditions
« Last Edit: November 24, 2018, 08:38:58 pm by CDaniel »
 

Offline chronos42

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #141 on: November 24, 2018, 10:32:43 pm »
Hi joeqsmith,

to make that more clear: Normaly I do not use a multimeter for measuring low pF values, I have other instruments for this.
But that is not the point. Also the drift is not my major problem.

The problem is: I Connect a capacitor in the pF range to my meter, switch it on and it shows (mostly) the correct value at the first try. Then I switch it off and on again while not touching anything except the switch and now I get a totally different value. Do the same again and I get another different value. When I switch off the meter again, wait some time, switch it on I get the correct value ....and so on...

That is a very strange behavior. I don't know whether this issue was from begin on or not, because I had never tried to measure a capacitor in the low pF range. I noticed this first time after you have mentioned the higher resolution in the capacitor mode and I checked this to look how the 121GW now performs compared with my other meters.
Just for fun.. I did not expect such a crazy behavior.

First I thougt that is a firmware bug of rev. 1.57, but it seems not so.
Your meter seems not affected from this issue as I can see in your video. But CDaniel seems to have the same problem like me.
BTW: Try also the mode button, does this also not affect your meter?

« Last Edit: November 24, 2018, 10:59:45 pm by chronos42 »
 

Online CDaniel

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #142 on: November 25, 2018, 01:01:18 am »
Yes , more or less I see the same behaviour like you , but not allways . The drifting I see is maybe that difference ...
With short probes it is not sensitive to touching the buttons ... but an issue is an issue , you can't make it dissapear . If you put the hands near the probes ... it's a mess  :--
And of course you can see the problem with larger capacitors 1nF-10nF , you don't have to measure something really small .
I doubt it's a hardware issue , they don't know very well to control the chip HY3131 with the firmware ... and if STM32 microcontroller is also new for them it's a very bad combination
« Last Edit: November 25, 2018, 01:07:21 am by CDaniel »
 

Offline 1anX

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #143 on: November 25, 2018, 04:02:17 am »
Hi joeqsmith,

to make that more clear: Normaly I do not use a multimeter for measuring low pF values, I have other instruments for this.
But that is not the point. Also the drift is not my major problem.

The problem is: I Connect a capacitor in the pF range to my meter, switch it on and it shows (mostly) the correct value at the first try. Then I switch it off and on again while not touching anything except the switch and now I get a totally different value. Do the same again and I get another different value. When I switch off the meter again, wait some time, switch it on I get the correct value ....and so on...

That is a very strange behavior. I don't know whether this issue was from begin on or not, because I had never tried to measure a capacitor in the low pF range. I noticed this first time after you have mentioned the higher resolution in the capacitor mode and I checked this to look how the 121GW now performs compared with my other meters.
Just for fun.. I did not expect such a crazy behavior.

First I thougt that is a firmware bug of rev. 1.57, but it seems not so.
Your meter seems not affected from this issue as I can see in your video. But CDaniel seems to have the same problem like me.
BTW: Try also the mode button, does this also not affect your meter?

Hey chronos what happens if you short the capacitor leads each time before turning on the meter?

By turning the meter on the first time I assume you are charging a discharged cap, but each time you turn off and test again, the cap is already charged from the previous test.

Could this account for the behavior you are seeing?
 

Offline 1anX

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #144 on: November 25, 2018, 06:39:42 am »
I thought I would run a couple of low cap tests on my meter with V1.57 firmware.

Measured 2 caps of given values, 15pF and 22pF which are at the extreme end of what the meter is capable of measuring and checked values against my DER EE DE-5000 LCR meter.

The GW121 displayed a combined meter and leads, (with alligator clips) capacitance of 0.175nF when turned on. I used the REL function to zero out the combined meter and lead capacitance and then measured each cap. I repeated the turning off and on of the meter and zeroing using the REL function before taking each measurement.

The 15pF cap measured 15.7pf on the DE-5000 and 0.018nF for the first 121GW test measurement and then 0.014nF for the second test.

The 22pf cap measured 22.9pf on the DE-5000 and 0.025nF for the first 121GW test measurement and then 0.021nF for the second test.

Considering the +-2.5%+5, I was pretty pleased with the meter's performance!
 
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Offline chronos42

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #145 on: November 25, 2018, 10:06:30 am »
hi joeqsmith and 1anX,

i noticed this issue first with firmware 1.57 and blamed this firmware, but i was wrong in this point, sorry for the missleading.

I also can get very accurate values in the low pF range, but only one time after the meter was laying around unused for some time. After switching on the first time it is within its specs.
So far so good.
But from now on the behavior is not predictable.
When I switch off and on it sometimes is spot on again, sometimes it reads about 80pF too less. When I use the mode button and step through the different modes until I am back to capacity mode it also reads 80pF too less. Switching off and on in this state does not reset the meter to a correct reading. I have to wait some time, then it comes back. The reading counts up with about 1pF all 15 seconds until it has reached the correct value again.

That makes it so hard to find out a predictable behavior.

For me that looks like a port that is not correctly set and floates in tristate mode. In this case there is no stable operation possible and everything can happen and also every meter can behave different.
« Last Edit: November 25, 2018, 09:41:15 pm by chronos42 »
 

Online CDaniel

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #146 on: November 25, 2018, 06:33:29 pm »
   

Sorry about the pictures being tilted  :-\

So , meter on the bench , no probes , no powerfull electric field nearby ( everything was shut down )
At first was 0.000 , and then slowly is drifting up ( in maybe 30min ) . Doesn't matter if is on or off . With leads connected is much faster and bigger . This offset is adding when I measure a real capacitor .
This is not something heating up inside , it is like some capacitor in the measurement path is charged by external electromagnetic field .
If I switch the rottary selector to off and then on again to capacitance nothing is changing .
To zero out this offset I have to cycle through cap manual ranges or to switch to resistance and back ...

I see that you are curious about the shim , my multimeter was bought from Welectron with it already installed ( I looked inside ) . And is working just fine ... for now  :P
« Last Edit: November 25, 2018, 06:49:10 pm by CDaniel »
 

Online CDaniel

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #147 on: November 25, 2018, 07:03:52 pm »
Mister  joeqsmith , if you read my post carefully I said that with leads the drift is faster and bigger .
I tested without probes on purpose so you can't say that I moved them or I did something ...   or my test capacitors are not good enough ;)
If you don't observe anything wrong doesn't mean that everybody else is stupid ...
« Last Edit: November 25, 2018, 07:19:18 pm by CDaniel »
 

Online CDaniel

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #148 on: November 25, 2018, 07:31:47 pm »
Some issues are hard to replicate if you don't have the exact meter , it was pre-production or modified in any way .
And the firmware was released just recently , before this , with low resolution , was useless to test small capacitors .
So be patient , if there are contradictions is because we are testing right now , ideas and observations can change .  Probably many others will test and share the results .
« Last Edit: November 25, 2018, 07:42:03 pm by CDaniel »
 

Online CDaniel

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Re: EEVBlog 121GW Multimeter Firmware Details
« Reply #149 on: November 25, 2018, 08:58:30 pm »
OK , I have read the HY3131 Configuration , but we can't know yet how the firmware is implemented . How the configuration bits are .

For the noise in resistance mode I discovered that they didn't used the input low pass capacitor C21 , now they fixed that . That's like using an ADC for DC without any capacitor at input , any electomagnetic field will make the reading to fluctuate .

Maybe this is something simple , or not ... if it is something hardware after all , that CMOS 4053  switch leakeage current is the first suspect  ;) 
In my shoping list are some  MAX4053 low leakeage switch                   



« Last Edit: November 25, 2018, 09:02:23 pm by CDaniel »
 


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