Author Topic: EEVBlog 121GW Discussion thread  (Read 626877 times)

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Offline dcac

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Re: EEVBlog 121GW Discussion thread
« Reply #1850 on: March 21, 2021, 01:26:07 pm »
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 believe the reason for using REL in the lowest mV range is to compensate for any temporary offset drift (usually) caused by temperature variations. In DC mV mode the signal passes through PTCs which can exhibit thermocouple behavior - then there’s i.e. also possible drift in the pre-amp and ADC.

In AC mV mode the signal has more or less the same path as DC but is then AC coupled right before the AD8436 RMS converter - so here it’s really only if the converter exhibits any drift you’d want to use the REL to cancel it out.

This description is for the 121GW but many other DMMs has much the same problem.
 

Offline dcac

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Re: EEVBlog 121GW Discussion thread
« Reply #1851 on: March 21, 2021, 01:48:01 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.


Perhaps a dedicated AC mV meter would be a better option - I don’t really have any specific to suggest though.

When I needed to measure sub mV Audio signals I built an external AC amplifier based on the OP37 opamp. Placed it in a battery powered small shielded box I could attach directly to a handheld DMM. I could set the amplification to 10, 100 or 200X and here the frequency response was perfectly flat 20Hz - 20KHz and a bit beyond. I don’t know if any such device exists ready to buy though.
 

Offline Keyview

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Re: EEVBlog 121GW Discussion thread
« Reply #1852 on: March 22, 2021, 11:29:28 am »
When I needed to measure sub mV Audio signals I built an external AC amplifier based on the OP37 opamp. [...] I don’t know if any such device exists ready to buy though.
I have never soldered before, so I would have to buy it - if it is for sale.
Your approach sounds somewhat similar to the eevblog uCurrent, but I am not sure if it measures uV AC.
Besides, the uCurrent is out of stock everywhere.

Please let me know if anyone has an idea where to get a (reasonably priced) AC amplifier to use with a DMM.
 

Offline skyjumper

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400mA fuse replacement
« Reply #1853 on: March 22, 2021, 03:26:56 pm »
Hi All, this weekend I blew the 400mA 600V fuse. I'm in the US, and Dave's fuse pack would take some time to get here. I see lots of 600V 500mA fuses available, not so much with the 400mA. Could I safely use a 500mA fuse instead?
 

Offline Wytnucls

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Re: EEVBlog 121GW Discussion thread
« Reply #1854 on: March 22, 2021, 05:41:26 pm »
The range is 500mA, so the 500mA 600V fuse is fine, if it has a FF rating (Fast) and a high breaking capacity (10kA).
6x32mm, rated for AC/DC (UL248-1)
« Last Edit: March 22, 2021, 05:50:18 pm by Wytnucls »
 
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Offline skyjumper

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Re: EEVBlog 121GW Discussion thread
« Reply #1855 on: March 22, 2021, 08:28:31 pm »
Thanks very much, I thought as much but this makes me wonder why there is a 400mA fuse to begin with? Although I did end up finding some 400mA @ 600V, are these acceptable:

https://www.amazon.com/gp/product/B0891P5XMM/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1
« Last Edit: March 22, 2021, 08:42:28 pm by skyjumper »
 

Offline Wytnucls

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Re: EEVBlog 121GW Discussion thread
« Reply #1856 on: March 22, 2021, 09:15:23 pm »
Stick to good brands, like Littelfuse, Cooper Bussmann or Siba if you can, otherwise examine the datasheet carefully for compliance.
The manual recommends  cryptically ASTM HV610.0.4 400 mA (600V) or HV620.0.4(1000V) A/500 mA current input fuse (sic)
 
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Offline skyjumper

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Re: EEVBlog 121GW Discussion thread
« Reply #1857 on: March 22, 2021, 09:18:00 pm »
Stick to good brands, like Littelfuse, Cooper Bussmann or Siba if you can, otherwise examine the datasheet carefully for compliance.
The manual recommends  cryptically ASTM HV610.0.4 400 mA (600V) or HV620.0.4(1000V) A/500 mA current input fuse (sic)

Ah okay, well if 1000V fuse is acceptable then there are many 500mA to choose from. Thanks.
 

Offline Brumby

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Re: EEVBlog 121GW Discussion thread
« Reply #1858 on: March 22, 2021, 11:53:00 pm »
 

Offline AVGresponding

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Re: EEVBlog 121GW Discussion thread
« Reply #1859 on: March 23, 2021, 09:49:29 am »
This:
Stick to good brands

And make sure the spelling is correct! Poor spelling invariably indicates counterfeits that have no sand inside to quench the fault arc, something I'm seeing more of in the UK with BS1362 fuses.
They can and do explode under fault loading.
nuqDaq yuch Dapol?
Addiction count: Agilent-AVO-BlackStar-Brymen-Chauvin Arnoux-Fluke-Hameg-HP-Keithley-IsoTech-Mastech-Megger-Metrix-Micronta-Racal-Siglent-Solartron-Tektronix-Thurlby-Time Electronics-TTi-UniT
 

Offline skyjumper

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Re: EEVBlog 121GW Discussion thread
« Reply #1860 on: March 23, 2021, 04:24:38 pm »
I have Dave's fuse pack on order, but that will take 15 days and I can't wait that long to get this back into service. I should have stocked up on fuses for it, but it never occurred to me they would be hard to find on short notice. In the meantime I'll use the one I ordered and be super careful not to screw up again. Maybe the international postal Gods will smile on me :-)
 

Offline EEVblog

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Re: EEVBlog 121GW Discussion thread
« Reply #1861 on: March 24, 2021, 07:40:13 am »
Stick to good brands, like Littelfuse, Cooper Bussmann or Siba if you can, otherwise examine the datasheet carefully for compliance.

Beware of fakes on ebay and other places. Because of the very high potential margins on these, the market is awash with fakes.
 
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Offline tmcks

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Re: EEVBlog 121GW Discussion thread
« Reply #1862 on: April 21, 2021, 02:04:39 am »
Hi all,

I received my 121GW today. I went to check the firmware and I see v2.04 is the highest listed on the 121GW firmware page, but the start screen on the DMM shows v2.05. Is this an error and I should flash 2.04, or is 2.05 real and just not listed yet?

Thanks.
 

Offline firewalker

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Re: EEVBlog 121GW Discussion thread
« Reply #1863 on: April 21, 2021, 09:43:31 am »
Hi all,

I received my 121GW today. I went to check the firmware and I see v2.04 is the highest listed on the 121GW firmware page, but the start screen on the DMM shows v2.05. Is this an error and I should flash 2.04, or is 2.05 real and just not listed yet?

Thanks.

Probably not listed yet. Check the contents of the microSD card. If you see a file named EEVBlog.bin, share it with us.  :D :D :D

Alexander.
Become a realist, stay a dreamer.

 

Offline tmcks

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Re: EEVBlog 121GW Discussion thread
« Reply #1864 on: April 21, 2021, 01:59:17 pm »

Probably not listed yet. Check the contents of the microSD card. If you see a file named EEVBlog.bin, share it with us.  :D :D :D

Alexander.

Sorry, but the SD card seems to be empty.
 

Offline EEVblog

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Re: EEVBlog 121GW Discussion thread
« Reply #1865 on: April 22, 2021, 01:35:01 am »
Hi all,
I received my 121GW today. I went to check the firmware and I see v2.04 is the highest listed on the 121GW firmware page, but the start screen on the DMM shows v2.05. Is this an error and I should flash 2.04, or is 2.05 real and just not listed yet?
Thanks.

I don't have have 2.05, have asked Kane what the deal is.
I have new stock on the way soon, don't know what version they will have. I can only presume that you bought it from Welectron and they somehow have a newer version firmware.
 

Offline tmcks

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Re: EEVBlog 121GW Discussion thread
« Reply #1866 on: April 22, 2021, 02:31:41 am »
Hi all,
I received my 121GW today. I went to check the firmware and I see v2.04 is the highest listed on the 121GW firmware page, but the start screen on the DMM shows v2.05. Is this an error and I should flash 2.04, or is 2.05 real and just not listed yet?
Thanks.

I don't have have 2.05, have asked Kane what the deal is.
I have new stock on the way soon, don't know what version they will have. I can only presume that you bought it from Welectron and they somehow have a newer version firmware.

Yes, it is from Welectron.

Thank you.
 

Offline EEVblog

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Re: EEVBlog 121GW Discussion thread
« Reply #1867 on: April 22, 2021, 02:56:09 am »
I now have v2.05
They changed the low pass filter curve to better match the performance of the Fluke 289, which I guess they are using as a sort of reference.
And yes, this version was shipped to Welectron.
 
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Online J-R

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Re: EEVBlog 121GW Discussion thread
« Reply #1868 on: April 22, 2021, 05:03:59 am »
Flashed without incident.
 
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Offline e0ne199

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Re: EEVBlog 121GW Discussion thread
« Reply #1869 on: April 27, 2021, 06:09:50 pm »
I now have v2.05
They changed the low pass filter curve to better match the performance of the Fluke 289, which I guess they are using as a sort of reference.
And yes, this version was shipped to Welectron.

is that the only update??
 

Offline EEVblog

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Re: EEVBlog 121GW Discussion thread
« Reply #1870 on: April 28, 2021, 12:55:40 am »
I now have v2.05
They changed the low pass filter curve to better match the performance of the Fluke 289, which I guess they are using as a sort of reference.
And yes, this version was shipped to Welectron.
is that the only update??

Yes. That is the only change they said was made.
 

Offline commandlinehool

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Re: EEVBlog 121GW Discussion thread
« Reply #1871 on: May 28, 2021, 01:21:31 pm »
Also got mine from electron today with 2.05. Also the yellow shim have been removed?

Does it always comes without probes? I thought it’s either Brymen or UEI probes.

Cheers
« Last Edit: May 28, 2021, 03:26:16 pm by commandlinehool »
 

Offline EEVblog

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Re: EEVBlog 121GW Discussion thread
« Reply #1872 on: May 29, 2021, 10:26:12 am »
Also got mine from electron today with 2.05. Also the yellow shim have been removed?

Yes, the shim was only for the first several thousand PCB's that had the wrong thickness.

Quote
Does it always comes without probes? I thought it’s either Brymen or UEI probes.

I don't have control over what Welectron sell, but Kane's standard FOB quote is without probes. If the distributor wants probes then they have to order them as a separate line item.
 

Online J-R

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Re: EEVBlog 121GW Discussion thread
« Reply #1873 on: May 30, 2021, 01:13:04 am »
By default Welectron checks the box to include the probes when you hit the 121GW page, but you can uncheck it.

I have two 121GW units that came with shims.  I removed it from both and have had zero issues.  Perhaps after things wear it might be needed.
 

Offline commandlinehool

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Re: EEVBlog 121GW Discussion thread
« Reply #1874 on: June 01, 2021, 11:50:17 am »
Also got mine from electron today with 2.05. Also the yellow shim have been removed?

Yes, the shim was only for the first several thousand PCB's that had the wrong thickness.

Quote
Does it always comes without probes? I thought it’s either Brymen or UEI probes.

I don't have control over what Welectron sell, but Kane's standard FOB quote is without probes. If the distributor wants probes then they have to order them as a separate line item.

Thx for the reply. I didn't know they aren't stock included. :)

By default Welectron checks the box to include the probes when you hit the 121GW page, but you can uncheck it.

I have two 121GW units that came with shims.  I removed it from both and have had zero issues.  Perhaps after things wear it might be needed.

Yeah, I thought there were some included, so I unchecked it  ;D.  Got myself some Fluke Probes now, maybe have to shorten the banana plugs a bit but otherwise they work fine.

Yeah, I wanted to remove them to avoid issues and found out they aren't there anymore. :)
 


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