Author Topic: EEVBlog 121GW Discussion thread  (Read 767236 times)

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Offline dcac

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Re: EEVBlog 121GW Discussion thread
« Reply #1825 on: July 26, 2020, 01:47:39 pm »
Thanks for the update - it wasn’t really anything urgent I needed to search for in that thread. So I'll just wait until it gets back online.

 

Offline dcac

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Re: EEVBlog 121GW Discussion thread
« Reply #1826 on: July 26, 2020, 01:54:00 pm »
I see you guys are working on it as we speak - just a note the restored thread does not have the 'pinned' status (yet).

 

Offline coromonadalix

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Re: EEVBlog 121GW Discussion thread
« Reply #1827 on: July 28, 2020, 01:40:00 am »
now pinned 
 

Offline oliv3r

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Re: EEVBlog 121GW Discussion thread
« Reply #1828 on: August 09, 2020, 08:32:05 am »
Hey all,

I seem to be stuck on the IAP- 'down' screen for some 20 minutes now, trying to update from 1.58 (beta) to 2.04. Any reason why? or should I just restart it ...

Offline Scottjd

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Re: EEVBlog 121GW Discussion thread
« Reply #1829 on: August 09, 2020, 09:00:18 am »
https://www.eevblog.com/forum/testgear/eevblog-121gw-multimeter-firmware-details/msg2828400/#msg2828400

If you downloaded the firmware and its in a zip package, you have to unzip/uncompress the file first.
Its important to make sure the new firmware file on the SD card is named “EEVBlog.bin” with no spaces in the file name or the meter might hang and just display down.
If the batteries are old then you might want to make sure you have a fresh set of batteries installed before running the firmware update. I think I’ve read the newer firmware will check the battery level first, but i’m not sure about that.

1. Turn the meter off then hold down MEM and HOLD while turning on the meter.  You will see IAP on the display.
2. Press the “SETUP” button and it will display “DOWN / DOUUN” and after 5 seconds the meter bar should start rising from the left to right.
3. Once the bar hits the end the meter will restart displaying the new version of firmware installed.
This whole process after it displays “DOWN / DOUUN” shouldn’t take more then 15 seconds.

Someday, maybe someday they will add a timeout to the firmware update menu so it will error out after say 3 to 5 minutes????
« Last Edit: August 09, 2020, 09:02:26 am by Scottjd »
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Offline oliv3r

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Re: EEVBlog 121GW Discussion thread
« Reply #1830 on: August 11, 2020, 01:56:48 pm »
https://www.eevblog.com/forum/testgear/eevblog-121gw-multimeter-firmware-details/msg2828400/#msg2828400

If you downloaded the firmware and its in a zip package, you have to unzip/uncompress the file first.
...
Thanks for that, (of course) I did all that, but the problem was far simpler. I forgot to move the SD card into the meter :D

Someday, maybe someday they will add a timeout to the firmware update menu so it will error out after say 3 to 5 minutes????
Which would have been super helpful in my case. But I think this is the built-in IAP code, so bootloader change, and remotely (via SD) not update-able? (update-able fine with st-link of course)

Online Brumby

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Re: EEVBlog 121GW Discussion thread
« Reply #1831 on: October 03, 2020, 06:05:57 am »
If I were Dave, I'd be rather interested to see what the actual cause of the failure was.......


Looks like the post was removed.
Yes, it has been.
« Last Edit: October 03, 2020, 10:38:16 am by Brumby »
 

Offline J-R

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Re: EEVBlog 121GW Discussion thread
« Reply #1832 on: February 10, 2021, 09:06:49 am »
Is there a discussion about the fact the 121GW is 99,999 count when in calibration mode?
 

Offline dcac

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Re: EEVBlog 121GW Discussion thread
« Reply #1833 on: February 10, 2021, 04:34:01 pm »
Is there a discussion about the fact the 121GW is 99,999 count when in calibration mode?

Not that I can recall - other than it’s been mentioned Agilent U1282 which is a 60,000 count meter also uses the HY3131.

And then there's this: https://reference.digilentinc.com/reference/add-ons/dmm-shield/reference-manual which is also based on HY3131 and claims to be a 5 1/2 digit meter.

But HY3131 is only rated for 50,000 count at a specified sample rate, accuracy and linearity in the datasheet. But it is in fact a 24bit ADC so theoretically you could get 2^23 or 8388608 count - in a perfect world that is.

But I noticed that too with 121gw in calibration mode that many modes/ranges acts as a 99,999 count meter. But I think the 5M and 50M ohms ranges only reaches 67,000 or something like that.
 

Offline J-R

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Re: EEVBlog 121GW Discussion thread
« Reply #1834 on: February 11, 2021, 06:25:03 am »
Ran a bunch of tests and was surprised that specifically all the DCV & DCmV ranges were quite accurate all the way up, for example 9.87654V on the calibrated supply was 9.8764V on the 121GW.  Past about 2 9's on the display and things were a bit off, however.

mA and A gained the extra headroom but the accuracy wasn't quite worth it.  Capacitance and resistance were spotty as well.  Some useful information could possibly be found under certain conditions.

Pushed 990V through it for about a minute with no issues.  It still beeped constantly despite happily displaying the correct voltage...
 

Offline skysurf76

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Re: EEVBlog 121GW Discussion thread
« Reply #1835 on: February 12, 2021, 08:18:56 pm »
Anyone have any idea how often Dave gets shipments of 121GWs?  I'm wanting to pick up another but they are currently out of stock.
 

Online Brumby

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Re: EEVBlog 121GW Discussion thread
« Reply #1836 on: February 12, 2021, 09:55:47 pm »
From what Dave has said recently, I don't think even he can answer that at the moment.  It appears there are supply issues with some of the components - which would make it difficult for even the manufacturer to give a date.
 

Offline skysurf76

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Re: EEVBlog 121GW Discussion thread
« Reply #1837 on: February 12, 2021, 10:54:44 pm »
I figured that might be the case. Thanks Brumby.
 

Offline J-R

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Re: EEVBlog 121GW Discussion thread
« Reply #1838 on: March 08, 2021, 11:03:48 pm »
Welectron has some in stock now.
 

Offline DeuxVis

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Re: EEVBlog 121GW Discussion thread
« Reply #1839 on: March 17, 2021, 04:50:42 pm »
I got a 121GW off the kickstarter campaign, Johnny B. Goode level

I never received a shim, is that because not all the kickstarter meters are affected by the pcb thickness problem ?

My range switch is behaving as expected by the way, just wondered.

Sorry I couldn't find the information in that very long thread, it's probably hiden somewhere inhere...


Thanks.
 

Offline J-R

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Re: EEVBlog 121GW Discussion thread
« Reply #1840 on: March 17, 2021, 06:10:24 pm »
Bought one a couple years back, removed the shim right away and have had no issues.
 

Offline EEVblog

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Re: EEVBlog 121GW Discussion thread
« Reply #1841 on: March 18, 2021, 12:03:15 am »
From what Dave has said recently, I don't think even he can answer that at the moment.  It appears there are supply issues with some of the components - which would make it difficult for even the manufacturer to give a date.

They are now saying April 30th. But I'm getting the feeling that's still based on a promise from component suppliers, I don't think they actually have all the parts in had at the moment.
FYI, Brymen are having production delays too due to component shortages.
 
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Offline Keyview

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Re: EEVBlog 121GW Discussion thread
« Reply #1842 on: March 18, 2021, 08:56:15 pm »
I have a question on the specifications in the user manual of the 121GW.

In most cases, the specifications of a multimeter are valid only for a certain part of the range, e.g. from 10% to 100% of a range.
This becomes relevant in particular in the lowest range.

As an example, the AC 50 mV range accuracy of the Fluke 289 is specified for 5% to 100% of range. Below 5% of range, extra 20 digits need to be added to accuracy. 
But for the 121GW, e.g. for AC V, no such restrictions apply.
It is simply stated for the 50 mV range as 1.2%+15 digits (for 45-400 Hz) without a lower bound.

So, I wonder whether the given specifications of the 121 GW are valid down to 0% of range.

Thank you!
 

Offline dcac

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Re: EEVBlog 121GW Discussion thread
« Reply #1843 on: March 19, 2021, 05:52:23 pm »
@Keyview

There might be a typo in the 121GW manual - the footnote (3) for 50mV DC probably also should apply to 50mV AC but here it refers to footnote (2)? which is not to be found.

   
 

Offline Keyview

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Re: EEVBlog 121GW Discussion thread
« Reply #1844 on: March 19, 2021, 11:53:27 pm »
There might be a typo in the 121GW manual - the footnote (3) for 50mV DC probably also should apply to 50mV AC but here it refers to footnote (2)? which is not to be found.
Thank you for sharing your observation on the potential typo.

I now checked with the Fluke 289 manual: The requirement for rel mode and zeroing for 50 mV DC is mentioned there, too, but no requirement for rel mode for 50 mV AC.
So, the footnote 2 on page 17 of the 121GW manual is maybe not to be read as footnote 3.

I consider to purchase the 121GW for low V AC measurements because it has a better accuracy than the Fluke 289 in this low area.
For example, measuring 1 mV AC with the Fluke 289 has an accuracy of 0.42 dB (65 Hz - 10 kHz). Whereas for the 121 GW it is 0.23 dB (45-400 Hz) and 0.34 dB (400 Hz - 5 kHz).

But maybe I should wait with the purchase until the footnote for the 50 mV AC range is clarified.
 

Offline J-R

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Re: EEVBlog 121GW Discussion thread
« Reply #1845 on: March 20, 2021, 05:42:15 am »
Accuracy specifications can be a poor metric in my opinion.  You have some equipment that just barely squeaks by and other equipment that exceeds the spec by a factor of 10 in some cases.

Got a bit carried away and tested a pile of my DMMs with a 3312A signal generator.  100.0000mV sine wave at 1KHz fed through a Gertsch RT-5 ratio transformer for a final output of 1mV.  (I picked those values because I have recent calibration data for the 34401A which states 100.0000mV is 99.9932mV at 1KHz.)

34401A -- 0.994mV
Fluke 287 -- 1.002mV
121GW #1 -- 0.989mV
121GW #2 -- 0.985mV
Fluke 87V -- 0.99mV
Fluke 88V -- 0.86mV
BM869s -- 0.99mV
BM789 -- 0.84mV
Agilent U1461A -- 1.010mV

I did not use relative mode on any of these.  All devices were powered up for a couple hours at 67F and allowed to settle before taking a reading.

After some further tinkering, I did notice the Fluke 287 drops to 0 around 0.150mV and the 34401A drops to 0.100mV at 0.300mV and to 0 around 0.200mV.
Both 121GW units had no trouble showing something meaningful down that low, so 0.100mV was 0.085mV and 0.050mV was 0.033mV for example...

I also ran the same tests at 200Hz and found the results to be virtually identical.

If my calculations are correct, the Fluke 287 was 0.02dB high, and the worst 121GW was 0.13dB low.

« Last Edit: March 21, 2021, 05:33:17 am by J-R »
 
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Offline dcac

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Re: EEVBlog 121GW Discussion thread
« Reply #1846 on: March 20, 2021, 08:12:06 am »
There might be a typo in the 121GW manual - the footnote (3) for 50mV DC probably also should apply to 50mV AC but here it refers to footnote (2)? which is not to be found.
Thank you for sharing your observation on the potential typo.

I now checked with the Fluke 289 manual: The requirement for rel mode and zeroing for 50 mV DC is mentioned there, too, but no requirement for rel mode for 50 mV AC.
So, the footnote 2 on page 17 of the 121GW manual is maybe not to be read as footnote 3.


Yes perhaps - the signal path for AC mV is quite different from DC mV and so is any possible offset that needs to be canceled out. I wonder what footnote (2) is about though. I found an older manual from 2017 that is different and with no footnote for AC mV.



 
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Offline Keyview

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Re: EEVBlog 121GW Discussion thread
« Reply #1847 on: March 20, 2021, 12:50:33 pm »
Got a bit carried away and tested a pile of my DMMs [...]
Thank you very much for your excellent analysis!
This convices me to order the 121GW.

If this performance is typical for a 121GW then it might be worth to explicitly add in the user manual that the specifications are valid down to 0% of range - for V AC and the other measurements.
Otherwise one might wonder whether stating a lower bound for the specifications has been forgotten.

Thank you for your and dcac's swift and competent feedback!
 

Offline J-R

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Re: EEVBlog 121GW Discussion thread
« Reply #1848 on: March 21, 2021, 06:44:53 am »
The mV relative mode statements in the manual makes no sense to me.  If the zero calibration point is off far enough that you need to REL the meter before taking a measurement, then the final reading will be off as well.  If you REL out noise/interference, same issue.

I think the larger issue here is that you need a way to verify your readings.  Don't blindly trust one DMM.  Using the function generator and the ratio transformer, I can easily make any of my DMMs display garbage values where they really shouldn't.  But frequently one DMM pulls through where another falls flat.  The inability of the 34401A and the 287 to display very low mV AC values surprised me a bit.  But they also both destroy the 121GW and Brymens with DCV accuracy all day long...
 

Offline Keyview

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Re: EEVBlog 121GW Discussion thread
« Reply #1849 on: March 21, 2021, 12:36:17 pm »
Don't blindly trust one DMM.
This is a key point. If I had (besides budget) more room, I would get a Keysight 34465 bench meter and a good handheld DMM, say Fluke 287/289.
(Btw, the Flukes are here in Europe twice the price of the US market prices.)

I am interested in low voltage AC (down to a few mV) for some audio connected measurements.
Ideally, I would find a handheld DMM with the accuracy of the 34465, but this does not exist.
I would also like to simply trust the product specifications to avoid having several quality devices that can measure (by specification) quite accurately down to 1 mV AC.
Not sure, if it is smart to fully trust the specifications. Maybe this is indeed blind trust.

The inability of the 34401A and the 287 to display very low mV AC values surprised me a bit.
Actually, the 287 does not meet its specifications with your observation that 0.150 mV 1 kHz is displayed as 0.
The accuracy as stated by Fluke should be 0.4% + 45 digits (0.001 mV) in this case.
 


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