Author Topic: EEVblog 121GW Multimeter Issues  (Read 163093 times)

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Offline 3db

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Re: EEVblog 121GW Multimeter Issues
« Reply #125 on: January 20, 2018, 09:58:39 am »
IIRC the point of not open-sourcing it is that messing with the firmware could affect the safety of the meter so there's no way they can officially sanction that or help people to do it.

Dave maybe can sell a version with open source firmware as DMM development kit? As a dev kit, you can basically bypass any certification requirements.

There is absolutely nothing stopping anyone writing their own firmware and making it open source.

Does that include YOU Dave ?
 

Offline EEVblog

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Re: EEVblog 121GW Multimeter Issues
« Reply #126 on: January 20, 2018, 10:16:31 am »
There is absolutely nothing stopping anyone writing their own firmware and making it open source.
Does that include YOU Dave ?

No, the ridiculous amount of time spent on the open source app taught us not to touch the firmware.
 

Offline ChrisG

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Re: EEVblog 121GW Multimeter Issues
« Reply #127 on: January 20, 2018, 10:46:14 am »
Confirmed issues (or annoyances) from what I've (re)-tested so far.

1. Slow auto-ranging: Ohms, Voltage, Capacitance
2. double double double beeps constantly going on when in diode mode
3. measuring any resistance (short or higher value) in diode mode gives a constant and loud beep
4. Wobbly selector/range switch: back an forth (vertical) when in diode mode it will even blink the back-light or completely switch off.
5. Strange to me is that when in diode mode a small green LED has a Vf of 1.79 in the 3V mode and a Vf of 1.98 in the 15V mode. And also is a bit brighter then.

Hope this helps,

6. on the lower current fuse is rated 600V and 400mA from ASTM. Which is different from the manual: 440mA and 1000V. I believe this was somewhere posted already?
« Last Edit: January 21, 2018, 02:17:08 pm by ChrisG »
 

Offline EEVblog

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Re: EEVblog 121GW Multimeter Issues
« Reply #128 on: January 20, 2018, 11:18:44 am »
3. measuring any resistance (short or higher value) in diode mode gives a constant and loud beep

That feature was requested by people.

Quote
5. Strange to me is that when in diode mode a small green LED has a Vf of 1.79 in the 3V mode and a Vf of 1.98 in the 15V mode. And also is a bit brighter then.

Expected, as they result in different test currents.
 
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Offline amspire

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Re: EEVblog 121GW Multimeter Issues
« Reply #129 on: January 20, 2018, 11:25:23 am »
Manual Correction Dec 11:

The manual specifications is a bit vague on diode test currents. It mentions 1.4mA and 7mA short circuit but they don't really line up with the 3V range and 15V ranges.

It seems the actual currents are different on my meter (v1.01):

3V    0.7mA short circuit
15V  4.6mA

Page 44 mentions the Diode Test current is limited by a resistor + PTC totalling about 2.2K. Has this changed?

ChrisG: Your point 5 is not an issue - the two diode tests are at two different currents. The voltages are meant to be different.
« Last Edit: January 20, 2018, 11:33:21 am by amspire »
 
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Online Fungus

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Re: EEVblog 121GW Multimeter Issues
« Reply #130 on: January 20, 2018, 01:38:01 pm »
The manual specifications is a bit vague on diode test currents. It mentions 1.4mA and 7mA short circuit but they don't really line up with the 3V range and 15V ranges.

It seems the actual currents are different on my meter (v1.01):

3V    0.7mA short circuit
15V  4.6mA

Short circuit current is a maximum. It will be less when there's no short circuit.
 

Offline amspire

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Re: EEVblog 121GW Multimeter Issues
« Reply #131 on: January 20, 2018, 03:12:29 pm »
The manual specifications is a bit vague on diode test currents. It mentions 1.4mA and 7mA short circuit but they don't really line up with the 3V range and 15V ranges.

It seems the actual currents are different on my meter (v1.01):

3V    0.7mA short circuit
15V  4.6mA

Short circuit current is a maximum. It will be less when there's no short circuit.

Huh?  I am just mentioning a case where the specifications for short circuit current and the actual meter are different. Also the formatting of the specifications does not have values lining up correctly. It may be the resistor in the final meter are different from the prototype meter. That is all. Dave has mentioned that he wants to soon release an updated version of the manual. It is part of the product.
« Last Edit: January 20, 2018, 03:15:20 pm by amspire »
 

Offline mikeselectricstuff

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Re: EEVblog 121GW Multimeter Issues
« Reply #132 on: January 20, 2018, 03:34:04 pm »
I wouldn't expect a low to mid-DMM diode check function to have particularly constant current.
Some quick checks on my meters over the reading range :
Fluke 87 (i and III) 0.8 to 0.15mA
Fluke 287 1mA up to 2V, then down to 0.8mA at 3v
Agilent 36641A 1mA constant
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Offline amspire

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Re: EEVblog 121GW Multimeter Issues
« Reply #133 on: January 20, 2018, 04:25:48 pm »
No one is suggesting constant current. I have done a report on short circuit currents of my meter because they are different from the spec. It would be useful if you can confirm my numbers, or if your 121GW meter matches the spec.
« Last Edit: January 21, 2018, 12:17:11 am by amspire »
 

Offline hwti

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Re: EEVblog 121GW Multimeter Issues
« Reply #134 on: January 21, 2018, 12:16:06 am »
No one is suggesting constant current. I have done a report on short circuit currents of my meter because they are different from the spec. It would be useful if you can confirm my numbers, or if your 121GW meter matches the spec. O miss
0.7mA on 3V range
4.25mA on 15V range
 
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Offline ChrisG

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Re: EEVblog 121GW Multimeter Issues
« Reply #135 on: January 21, 2018, 01:39:50 pm »
No one is suggesting constant current. I have done a report on short circuit currents of my meter because they are different from the spec. It would be useful if you can confirm my numbers, or if your 121GW meter matches the spec. O miss
0.7mA on 3V range
4.25mA on 15V range
0.71 mA on 3V range
4.61 mA on 15V range

Measured through a BM869s.
 

Offline EEVblog

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Re: EEVblog 121GW Multimeter Issues
« Reply #136 on: January 22, 2018, 03:48:27 am »
UPDATE:
UEi are aware of the various issues and are working on them.
The autoranging as you might expect is not necessarily trivial and will take a few more days to test this.
For the range switch they are waiting on a slightly modified part to see if that can solve it.
 

Offline amspire

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Re: EEVblog 121GW Multimeter Issues
« Reply #137 on: January 22, 2018, 04:14:45 am »
If UEi are fixing the Autoranging, it might be a good opportunity to fix the non-working DC mVA/VA autoranging with negative currents.
 

Offline borealis

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Re: EEVblog 121GW Multimeter Issues
« Reply #138 on: January 22, 2018, 02:50:08 pm »
Hi Dave

On my meter pins PE13 (SPI1_SCK/FSMC_D10) and PE14 (SPI_MISO/FSMC_D11) of the STM32L1 are shorted together (continuity tested). The attached file has the best focused image I could get of this. Should I do anything about it?
 

Offline zaoka

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Re: EEVblog 121GW Multimeter Issues
« Reply #139 on: January 23, 2018, 09:57:44 pm »
Metal parts in range switch will make it more enjoyable to use...
 

Offline EEVblog

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Re: EEVblog 121GW Multimeter Issues
« Reply #140 on: January 23, 2018, 10:39:06 pm »
On my meter pins PE13 (SPI1_SCK/FSMC_D10) and PE14 (SPI_MISO/FSMC_D11) of the STM32L1 are shorted together (continuity tested). The attached file has the best focused image I could get of this. Should I do anything about it?

That's VSSA and VREF-, they should be connected.
Looks like they used a direct track in-between pins which trapped the solder.
Nothing to worry about.
 

Offline benst

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Re: EEVblog 121GW Multimeter Issues
« Reply #141 on: January 23, 2018, 11:51:59 pm »
The switch on my meter (#000499) is also wobbly and has the problem described here.

I took it apart, and contacts and pcb looked ok. After I put it back together it worked allright for a while, but now it's back and I have to fiddle with the switch again to get it to display correct readings. :-BROKE

Dave, once UEi figures out a fix, will you send out a replacement part?

Thanks,
Ben
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Offline EEVblog

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Re: EEVblog 121GW Multimeter Issues
« Reply #142 on: January 24, 2018, 12:06:08 am »
The switch on my meter (#000499) is also wobbly and has the problem described here.
I took it apart, and contacts and pcb looked ok. After I put it back together it worked allright for a while, but now it's back and I have to fiddle with the switch again to get it to display correct readings. :-BROKE
Dave, once UEi figures out a fix, will you send out a replacement part?

Yes we'll have to do that for those existing shipments who have problems.
 
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Offline dr.diesel

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Re: EEVblog 121GW Multimeter Issues
« Reply #143 on: January 24, 2018, 12:38:35 am »
Minor Issue:

I just opened my 2nd set of leads, note the positive lead, recessed threaded portion, and it's broken internally.  Slightly flexing the break in the 2nd photo to accentuate the area.

It's electrically connected however.  (Replacements not necessary, I got a zillion of them)


Offline Scottjd

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Re: EEVblog 121GW Multimeter Issues
« Reply #144 on: January 24, 2018, 12:59:14 am »
Minor Issue:

I just opened my 2nd set of leads, note the positive lead, recessed threaded portion, and it's broken internally.  Slightly flexing the break in the 2nd photo to accentuate the area.

It's electrically connected however.  (Replacements not necessary, I got a zillion of them)

It happens in large numbers. My BM235 with the same probes has done that the inside spins on when I screw on the banana jacks. So I’ve just been carful to not torque that one since I fear the wire might eventually twist to much and break off. I even had one probe new with the fluke 289 that was bent, they did replace that one since they reached out to me. I guess they saw it on the unboxing video.
I never bothered to mention it since I have the probematers and a few fluke probes. Like you, I have enough of them, but sometimes I have to run three meters and I usually use the probes they came with.

That brings up a good question, I know Brymen is responsive to fixing and communicating with customers to fix issues. So if the probes have an issue, who do we contact since Brymen makes the probes but UEI made the meter? Do we contact UEI, Brymen, or EEVBlog (Dave)?

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Offline dr.diesel

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Re: EEVblog 121GW Multimeter Issues
« Reply #145 on: January 24, 2018, 01:04:30 am »
inside spins

This one is tight, perhaps just in the wrong position when molded.

I suspect the wire lead is terminated at the break in my case above, which means it probably wouldn't last long in the field.

Offline Kean

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Re: EEVblog 121GW Multimeter Issues
« Reply #146 on: January 24, 2018, 03:38:52 pm »
Just confirming an issue reported by Joe Smith on the prototype unit he tested still exists on my production unit.
As posted in the discussion thread at https://www.eevblog.com/forum/testgear/eevblog-121gw-discussion-thread/msg1408767/#msg1408767
And confirmed by maukka in a followup post https://www.eevblog.com/forum/testgear/eevblog-121gw-discussion-thread/msg1408768/#msg1408768

I wonder if someone could check the meter in the LowZ mode.   In the early unit, if I applied a 1VRMS 60Hz signal, the meter would read zero as expected.   However, when I would increase the frequency to 389KHz, the meter was displaying 181.3 volts even though there was still only a volt being supplied.   There was something strange going on with it that I never looked into.  I reported the problem when I discovered it but with as many problems that the meter still has, I wonder if this was addressed in the released version.

Joe, I can confirm this issue is still present in FW1.01.
I generated a 2.8Vpp 60Hz (& 1kHz) sine wave with my MSO1104Z-S and it read 0V in LowZ mode.
When I upped the freq to 389kHZ and I got a reading of 189.2Vac.  See photo...

Edit: and it correctly read ~1V AC without LowZ up to maybe 100kHz, but that dropped to 0.773V AC at 389kHz
 

Offline ChrisG

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Re: EEVblog 121GW Multimeter Issues
« Reply #147 on: January 24, 2018, 05:04:21 pm »
Confirmed... Though it does too vary a bit when changing frequencies.

 

Offline tpw_rules

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Re: EEVblog 121GW Multimeter Issues
« Reply #148 on: January 24, 2018, 10:19:27 pm »
Does this LowZ issue happen in the ACV's highest (600V) range? The two are calculated virtually identically in the software. If there's an issue with the routines or calibration data for that ACV mode, they should be broken in the same way. Of course, I'm not saying that them not behaving the same means it has to be fixed in hardware.

Edit: the calibration tables are also only specified up to 10KHz. Perhaps the 10KHz correction factor becomes invalid at such a high frequency? Can anyone dump their calibration data (requires firmware 1.02) for me?
« Last Edit: January 24, 2018, 10:37:56 pm by tpw_rules »
 

Offline Iagash

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Re: EEVblog 121GW Multimeter Issues
« Reply #149 on: January 24, 2018, 11:32:19 pm »
Edit: the calibration tables are also only specified up to 10KHz. Perhaps the 10KHz correction factor becomes invalid at such a high frequency? Can anyone dump their calibration data (requires firmware 1.02) for me?

Here you go, I attach it zipped.
 


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