Author Topic: EEVBlog 121GW Discussion thread  (Read 501509 times)

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Offline Zom-B

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Re: EEVBlog 121GW Discussion thread
« Reply #925 on: July 19, 2018, 01:31:37 pm »
Meter arrived.
  • I didn't expect an SD card so I readied one and was pleasantly surprised,
  • By default the beep is off ???, which threw me off because the manual said I had to press Setup till I hear a beep before any setting is saved,
  • The rubber boot is warped on the left side, not that I care,
  • The Android app is completely useless, and I see many others with similar problems,
  • I dislike the new 'yellow' of the temperature probe. It looks like it's been discoloring since the 30's, and the 'red' of the lead is more orange than the ends,
  • I don't know if the rubber tube around the temperature probe is for protection or not, but I found a new use: With the front of the tube flush with the weld point, I can push the probe tightly against a surface without fearing that the probe will bend or that I'll introduce a temperature influence.
« Last Edit: July 19, 2018, 01:38:49 pm by Zom-B »
 

Offline FrankBuss

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Re: EEVBlog 121GW Discussion thread
« Reply #926 on: July 19, 2018, 11:52:03 pm »
The 1 MOhm range is quite noisy, and 10 MOhm is way off:




It has a 5 MOhm and 50 MOhm range. According to the manual, the 50 MOhm range has a +/-1.2% accuracy. Looks like your meter has a +1.9% error in this range. I wouldn't say that's way off, but technically you are right, looks like it doesn't meet the specification.
So Long, and Thanks for All the Fish
Electronics, hiking, retro-computing, electronic music etc.: https://www.youtube.com/c/FrankBussProgrammer
 

Offline Dr. Frank

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Re: EEVBlog 121GW Discussion thread
« Reply #927 on: July 20, 2018, 06:50:34 am »


It has a 5 MOhm and 50 MOhm range. According to the manual, the 50 MOhm range has a +/-1.2% accuracy. Looks like your meter has a +1.9% error in this range. I wouldn't say that's way off, but technically you are right, looks like it doesn't meet the specification.


That was a quick 'n dirty check only, but in the meantime I made an overview of most modes and ranges.

These are mostly a factor of ten more accurate than in the specification, as would be required by proper bandguarding  guardbanding ratio, and also for the annual drift.
A high bandguarding guardbanding ratio is always an indicator, that the instrument was properly designed.. Keysight or Fluke DMMs are always much more precise, than their specification tells.

The 500k Ohm, 5 MOhm and 50MOhm ranges stand out in this aspect, as these are either spuriously unstable, or are on the edge, or over the limits of their specifications.

examples:
500k : +0.02% (compared to 0.2% spec.) and noisy,
but: 1.9M +0.2% (compared to 0.3% spec) and noisy
and: 19M +1.4%, that's been another measurement, (compared to 1.2% spec), and unstable with longer time constant


That's both a bad indicator, that there is something fishy.. others also already reported  about that instability of these Ohm ranges.

I assume, that due to this instability, initial calibration was also affected.

Frank

PS.: I will post the complete verification table later
« Last Edit: July 20, 2018, 12:15:16 pm by Dr. Frank »
 

Offline firewalker

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Re: EEVBlog 121GW Discussion thread
« Reply #928 on: July 20, 2018, 08:03:37 am »
For the rest of you (waiting from Welectron), do you see the parcel being processed daily? Mine is at

Code: [Select]
Bruchsal, Germany.

The international shipment has been processed in the parcel center of origin

Since Wednesday.
Become a realist, stay a dreamer.

 

Offline Jon.C

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Re: EEVBlog 121GW Discussion thread
« Reply #929 on: July 20, 2018, 08:27:23 am »
For the rest of you (waiting from Welectron), do you see the parcel being processed daily? Mine is at

Code: [Select]
Bruchsal, Germany.

The international shipment has been processed in the parcel center of origin

Since Wednesday.

yes

 

Offline Zom-B

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Re: EEVBlog 121GW Discussion thread
« Reply #930 on: July 20, 2018, 08:45:09 am »
I've never heard of bandguarding ratio and a few Google searches also turn up nothing.

[Edit] From the context it sounds like either Test Accuracy Ratio or Test Uncertainty Ratio (found on a metrological page)
« Last Edit: July 20, 2018, 08:50:15 am by Zom-B »
 

Offline HKJ

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Re: EEVBlog 121GW Discussion thread
« Reply #931 on: July 20, 2018, 08:48:52 am »
For the rest of you (waiting from Welectron), do you see the parcel being processed daily? Mine is at

For me there is another tracking number on the DHL site I can use with the local postal service and this morning it arrived at the local distribution center.
 

Offline firewalker

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Re: EEVBlog 121GW Discussion thread
« Reply #932 on: July 20, 2018, 09:12:59 am »
For the rest of you (waiting from Welectron), do you see the parcel being processed daily? Mine is at

Code: [Select]
Bruchsal, Germany.

The international shipment has been processed in the parcel center of origin

Since Wednesday.

yes



:( :( :(

Become a realist, stay a dreamer.

 

Offline Finder

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Re: EEVBlog 121GW Discussion thread
« Reply #933 on: July 20, 2018, 09:55:41 am »
« Last Edit: July 20, 2018, 10:15:27 am by Finder »
 

Offline firewalker

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Re: EEVBlog 121GW Discussion thread
« Reply #934 on: July 20, 2018, 10:04:59 am »
I don't know why normal post was used to send the meters out.

Alexander.
Become a realist, stay a dreamer.

 

Offline firstcolle

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Re: EEVBlog 121GW Discussion thread
« Reply #935 on: July 20, 2018, 10:06:05 am »
mine is "out for delivery" with DHL express
 

Offline firewalker

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Re: EEVBlog 121GW Discussion thread
« Reply #936 on: July 20, 2018, 10:07:36 am »
mine is "out for delivery" with DHL express

Yours was sent with DHL express?
Become a realist, stay a dreamer.

 

Offline firstcolle

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Re: EEVBlog 121GW Discussion thread
« Reply #937 on: July 20, 2018, 10:14:08 am »
mine is "out for delivery" with DHL express

Yours was sent with DHL express?

was sent via DHL post, i suppose..
 

Offline hammy

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Re: EEVBlog 121GW Discussion thread
« Reply #938 on: July 20, 2018, 10:47:27 am »
That's both a bad indicator, that there is something fishy.. others also already reported  about that instability of these Ohm ranges.

Just a observation: The noise is much less, if you put a precision resistor directly into the socket. A measurement with leads is way more noisy.
Not unusual for a DMM for this price.
 :-/O
« Last Edit: July 20, 2018, 11:00:25 am by hammy »
 

Offline Dr. Frank

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Re: EEVBlog 121GW Discussion thread
« Reply #939 on: July 20, 2018, 12:28:06 pm »
I've never heard of bandguarding ratio and a few Google searches also turn up nothing.

[Edit] From the context it sounds like either Test Accuracy Ratio or Test Uncertainty Ratio (found on a metrological page)

Nope, was kinda typo, or Freudian Error, I meant Guardbanding.

That's a different story than the simple T.U.R. ..

It means that you judge a calibration to be 'Fail', if the measured value is too close at/below the specification limit, so you define an additional band of tolerance to safeguard the calibration against additional sources of error.

It's explained here, by Keysights Chief Metrologist, Bob Stern:

In this context, a freshly calibrated instrument should always be far below the specified limits, otherwise it would be an indicator, that either there's something wrong with the calibration, or with the instrument under test.

That same way, I also found out in 2015, that my then brand new 34465A had several bugs in the firmware for the high voltage dc ranges, 100V and 1kV. And also that the KS calibration verification for this instrument contained a gap.

Frank
« Last Edit: July 20, 2018, 12:29:54 pm by Dr. Frank »
 
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Offline Dr. Frank

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EEVBlog 121GW Discussion thread - Initial Verification
« Reply #940 on: July 20, 2018, 02:44:46 pm »
Here we go,

I have compiled the basic accuracy verification, (comma used for the decimal point.)



All ranges are very well inside the (barn door wide) specification, mostly a factor of 10 more accurate than specified.

The linearity of the A/D_1 is quite good, but it shows a very pronounced Rollover Error of about 3 6 digits. I've expressed these both characteristics commonly by the overall DNL, Differential Non Linearity, over the nominal +/- 5.0000 V range, which computes to 2 digits, which is quite OK.




Only the 500k, 5M and 50M Ohm ranges show a strange behavior.

500k and 5M might be quite jumpy all of a sudden, or rock stable the other instance, always with the same physical setup.
The accuracy changes from one day to the other, or from one power-on to the other.
Latter goes also for the 50M range, which integrates much slower; 2 days ago it was out of specification, as it was today morning, but in the afternoon, it was inside spec, but varying from one power-on to the other.

Seems to me, that some internal interference occurs, as if the firmware creates spurious interrupts which affect the readings.

I monitored these different behaviors and will report elsewhere.

Otherwise, that instrument seems to be of very good quality, but not so well specified or qualified by UEI.
I think, that it performs much better, in the same league like other, more expensive DMMs.

Frank
« Last Edit: July 20, 2018, 07:14:10 pm by Dr. Frank »
 
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Offline HKJ

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Re: EEVBlog 121GW Discussion thread
« Reply #941 on: July 20, 2018, 04:18:48 pm »
It arrived today, that was 3 days from Germany, same time as DHL can move a parcel from China to me.
The meter was with V1.22 software, i.e. the newest
 

Offline DavidDLC

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Re: EEVBlog 121GW Discussion thread
« Reply #942 on: July 20, 2018, 10:55:17 pm »
Auto-range broken on V1.22

At work I'm measuring resistance and the auto-range cycles for ever. If I remember correctly there was an issue with this in the past and it was fixed with firmware change

In my case there is a capacitor that gets charged when measuring resistance. I did the same test with a Fluke in auto-range with no problem

Any comments ?

David DLC
 

Offline Zom-B

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Re: EEVBlog 121GW Discussion thread
« Reply #943 on: July 21, 2018, 04:12:27 pm »
Auto-range broken on V1.22

At work I'm measuring resistance and the auto-range cycles for ever. If I remember correctly there was an issue with this in the past and it was fixed with firmware change

In my case there is a capacitor that gets charged when measuring resistance. I did the same test with a Fluke in auto-range with no problem

Any comments ?

David DLC
Better move that to the 121 issues thread in the same subforum
 

Offline bicycleguy

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Re: EEVBlog 121GW Discussion thread
« Reply #944 on: July 21, 2018, 10:13:55 pm »
Tried some more data logging of my freezer, 2 days, 18 hours at 10 second intervals.  Observations:
1. 23690 measurements, no missed or corrupted data.
2. Partially discharged Energizer NiMH batteries dropped from 5.21 to 5.02V so could probably go a week with a fresh charge.
3. Not able to check battery (on display) during logging  :(.  Also the 4.2V warning is to low for NiMH if you want them to last... I know thats not what it's for.

4. My freezer defrost cycle is not time synchronous so I can't predict when to eat soft ice cream  :(
5. With regard to some of the temp spikes my wife admits to sticking her head in the freezer after working in the garden  |O
 
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Offline firstcolle

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Re: EEVBlog 121GW Discussion thread
« Reply #945 on: July 22, 2018, 11:21:44 am »
I'm doing some tests and i have some trouble with the uA range.

I set up a basic led circuit and measured the current on the mA range and the probe inserted into the A/500mA socket, the led is powered on and i measured 9mA.
I switched the range into the uA range and the probe into the mA/uA socket but the led does not power on and nothing is measured on the meter. I checked the 400mA fuse and there is no continuity... fuse blown?? I think that this range should measure 9mA..
 

Offline Robreeves

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Re: EEVBlog 121GW Discussion thread
« Reply #946 on: July 22, 2018, 02:17:03 pm »
What is the status of US distribution?  I am backer 878 and I have heard nothing.   :(
 

Offline bicycleguy

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Re: EEVBlog 121GW Discussion thread
« Reply #947 on: July 22, 2018, 05:22:25 pm »
I'm doing some tests and i have some trouble with the uA range.

I set up a basic led circuit and measured the current on the mA range and the probe inserted into the A/500mA socket, the led is powered on and i measured 9mA.
I switched the range into the uA range and the probe into the mA/uA socket but the led does not power on and nothing is measured on the meter. I checked the 400mA fuse and there is no continuity... fuse blown?? I think that this range should measure 9mA..
The maximum allowed in the uA position is 500uA so should indicate OFL.  It takes a second to show.  Fuse should have continuity.  Does probe in mA/uA socket, switch in ma work?

Finding the maximum range for each position is a little problematic.  The chart on page 16 of manual is useful if available.  The auto range position doesn't indicate the max just the current auto range.
So you have to:
1. With probes not hooked up but inserted into desired sockets (required for current)
2. Rotate switch as desired.
3. Select mode.
4. Press range and note the max range value in the lower right corner of display.  Continue pressing range until you find the max.

I don't think this is much different than other meters but the text for the value is so miniature I can't even see it without my glasses.  On other meters it is much more prominent.


« Last Edit: July 22, 2018, 05:40:15 pm by bicycleguy »
 

Offline sebmadgwick

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Re: EEVBlog 121GW Discussion thread
« Reply #948 on: July 22, 2018, 09:03:26 pm »
Hi Dave and Dave2.  I guess this is the best thread for some quick UI feedback concerning the printing on the plastic:

1) Don't print the backlight icon in yellow.  Doing so suggests that the yellow icon is linked to the yellow button in the same way that the red icons are linked to the red button.  It is not.  The backlight icon should be in white.

2) The the alternative 'red' modes for each rotatory position should not be remembered in software as this (a) breaks the relationship between red icons and the red button, and (b) means that you have to check that the mode is correct immediately after selecting a mode.  Even just writing that sentence spells out a clear UI fail.

3) I'll accept this last one as subjective but make the Bluetooth icon white.  There is no blue button but the icon colour suggests meaning where there is none.

..otherwise, I really like the meter :) Well done.
 

Offline Seppy

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Re: EEVBlog 121GW Discussion thread - Initial Verification
« Reply #949 on: July 23, 2018, 02:14:27 am »
Here we go,

I have compiled the basic accuracy verification, (comma used for the decimal point.)



All ranges are very well inside the (barn door wide) specification, mostly a factor of 10 more accurate than specified.

The linearity of the A/D_1 is quite good, but it shows a very pronounced Rollover Error of about 3 6 digits. I've expressed these both characteristics commonly by the overall DNL, Differential Non Linearity, over the nominal +/- 5.0000 V range, which computes to 2 digits, which is quite OK.




Only the 500k, 5M and 50M Ohm ranges show a strange behavior.

500k and 5M might be quite jumpy all of a sudden, or rock stable the other instance, always with the same physical setup.
The accuracy changes from one day to the other, or from one power-on to the other.
Latter goes also for the 50M range, which integrates much slower; 2 days ago it was out of specification, as it was today morning, but in the afternoon, it was inside spec, but varying from one power-on to the other.

Seems to me, that some internal interference occurs, as if the firmware creates spurious interrupts which affect the readings.

I monitored these different behaviors and will report elsewhere.

Otherwise, that instrument seems to be of very good quality, but not so well specified or qualified by UEI.
I think, that it performs much better, in the same league like other, more expensive DMMs.

Frank

We have tested 10 units now all within spec for 10 M, is there any chance environmental noise made the measurement wobbly? We can test more, but it is going to take some time.
 


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