EEVblog 121GW Multimeter Issues

[lewis]

...CONFIRMATIONS of those bugs and issues.

I can confirm the meter beeps and beeps and beeps and beeps and beeps and beeps and BEEEEEEEPPPPS which makes it basically unusable, because I BEEP, I mean keep, wanting to throw it at great BEEP, I mean speed, across the workBEEP, I mean workshop. I've taken back off and covered the sounder in many layers of tape but it's still annoying as hell.

I can also confirm It also takes about 9 seconds to measure a low resistance. The fuse rating printed on the back label does not match the fuse inside (440mA 1kV vs 400mA 600V). Update rate on the bluetooth app is abysmal, and the connection keeps dropping out. I don't know if the measurement displayed on the smartphone is what the meter is actually measuring, or if the connection has died.

If I remember correctly, there is also a large-ish offset under an open-probe condition on AC and DC voltage ranges (will edit this post later when I have the meter in my hand to confirm). Nope! mV range was showing on display, but selector switch was set to V! Had a -0.5mV DC offset, thought it was -0.5V. I think I had a dicky selector switch, very difficult to reproduce now the switch has had some (ab)use.

Dave, I can't see how you would have approved the prototype and thought it acceptable.

Beep <shudder>

[exe]

Firmware Version 1.01 has an extra setup field "00000" not mentioned in the manual. It is between the hour-minute setting and logging interval setting.

I thought it's a logging interval or screen refresh interval in ms... Or a sample number... Uhm...

[MatthewEveritt]

It's apparently a sort of 'serial number' that gets added to the bluetooth data to help distinguish multiple meters [source].

[Iagash]

While I consider the autoranging speed not particularly good, it is at least correct and works.

The fails in the adnvanced functions, that distinguish this meter from the rest of the market are much more annoying. They are not just "slow", they are plain unreliable and broken.

After fanOfeeDIY showed the broken logfile I decided to do a test to the maximum extend the meter logs.

I don't get why there is a limitation on 600k lines, but well, maybe Dave will explain some day or it's extended.
The 600k lines don't even last 48h.
I know I could reduce the log interval, but why?

I got the corrupt logfile in my first try.

The data is corrupted as bellow in the middle of the data.
59625,DCV,049.997,V,,,,,,,,
59626,DCV,049.997,V,,,,,,,,
59627,DCV,049.996,V,,,,,,,,
59628,DCV,049.997,V,,,,,,,,
59629,DCV,                                                                                                                                                                                        59641,DCV,050.001,V,,,,,,,,
59642,DCV,049.996,V,,,,,,,,
59643,DCV,049.996,V,,,,,,,,
59644,DCV,049.998,V,,,,,,,,
59645,DCV,049.996,V,,,,,,,,

The garbled line only happened in one line out of four files of data logging.

It looks to me as if samples 59629 through 59640 are missing from the file? So it's not just a garbled line, it's some dropped data.

Good comment, I should have attached the raw data of the log file from the beginning why I thought it was a garbled line.

I just opened the file with binary editor.

I can confirm the file corruption. I let the meter log for almost 2 days in VA mode and have several corrupted lines in the log.

I ran a small awk script on the file to find lines where the line counter didn't match the actual line number of the log lines.

Code: [Select]

awk -F, '/^[0-9]+,/{if ( c != $1 ) { printf("%6d %6d %s\n", l, c, $0); c = $1 } c++; l++; }BEGIN{l=1;c=1}' < 18011500.CSV
It prints the real line number, the line number it expected and the line from the logfile. The result is this:

Code: [Select]

61501  61501 61502,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
139554 139555 139562,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
243949 243957 243962,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
267167 267180 267182,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
344797 344812 344822,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
356188 356213 356222,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
412106 412140 412142,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
431304 431340 431342,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
478699 478737 478742,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
523695 523738 523742,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,

So there are 10 errors in just one logfile.

Here are the errors:

Code: [Select]

61499,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.53,mA,,
61500,DCVA,01959.5,mVA,DC^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@61501,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
61502,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,


Code: [Select]

139553,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.53,mA,,
139554,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,044^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@139561,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
139562,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,


Code: [Select]

243956,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.53,mA,,
24395^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@243961,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
243962,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,


Code: [Select]

267178,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.53,mA,,
267179,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.53,mA,^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@267181,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
267182,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,


Code: [Select]

344810,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.53,mA,,
344811,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.53,mA,^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@344821,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
344822,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,


Code: [Select]

356212,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.53,mA,,
35621^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@356221,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
356222,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,


Code: [Select]

412138,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.53,mA,,
412139,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.53,mA,^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@412141,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
412142,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,


Code: [Select]

431338,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.53,mA,,
431339,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.53,mA,^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@431341,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
431342,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,


Code: [Select]

478735,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.53,mA,,
478736,DCVA,01959.5,mVA,DCV,0^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@478741,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
478742,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,


Code: [Select]

523736,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.53,mA,,
523737,DCVA,01959.5,mVA,DCV,04.4482,V^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@523741,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,
523742,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.52,mA,,

The last logline in the file is:

Code: [Select]

600000,DCVA,01959.5,mVA,DCV,04.4482,V,DCA,0440.53,mA,,

So logging stops after the meter thinks it logged 600k lines, but in reality it logged only 599956 lines.

Interestingly the display counted to more than 600.00k lines. The highest value I saw on the display was 602.xxk lines (I don't remeber the xx).

So on the display it either kept counting after it stopped logging or didn't number and write all lines it actually thought it logged.

In the end there was "SDend" displayed and the "MEM" LCD-segment was not active anymore.

I can't attach the logfile since the forum says it's too big (even zipped it is 1.7MB). But I can send it to anybody who is interested.

[lowimpedance]

Bug/mechanical issue in the Diode test mode. When selected if you jiggle the plugs at the meter you get the short double beep and sometimes a continuous beep which requires further lead or switch jiggles to stop. So the switch seems to be very sensitive mechanically to trigger the continuous beep. Also via some PCB flexing (i guess), due to the test lead plugs will also trigger the beep.

Others can test to confirm.
As Dr diesel noted the temperature display is on until the range button is pressed for either 3 or 15v test.

Also to note that continuity function sometimes does not work either(similar switch issue?).
Ohms appears unaffected by any mechanical jiggling.

firmware 1.01

[amspire]

Bug/mechanical issue in the Diode test mode. When selected if you jiggle the plugs at the meter you get the short double beep and sometimes a continuous beep which requires further lead or switch jiggles to stop. So the switch seems to be very sensitive mechanically to trigger the continuous beep. Also via some PCB flexing (i guess), due to the test lead plugs will also trigger the beep.

firmware 1.01

I do not get the jiggling issue, but for some reason, when the diode mode senses any change (like a 10K resistor or anything else), it double beeps and then a second later double beeps again. Not sure why that is wanted. If the probes are shorted, it beeps continuously just like the continuity test mode.

Also in diode mode, the bar graph seems to be not normalised for the measurement. In the default 3V diode mode, the bar graph is at 60% on open circuit. For the 15V mode, it is at 33% on open circuit. These correspond to the positions the bar graphs would be in the 5V and 50V DC ranges respectively. A minor issue, but it probably should be tidied up.

Edit: Looking closely at the bar graph and it goes from 0 to 5. So it is on 3 for the 3V range and 1.6V (16V) on the 15V diode range. I guess that makes sense.

firmware 1.01 Diode Mode

[lowimpedance]

By jiggling I mean moving the lead plugs intentionally forward and back "a bit" in their sockets causes the continuous beep to engage with out shorting the probes together. And further to this once the continuous beep has started I can remove the probes from the meter and it carries on beeping until I "wiggle" the selector switch a little bit then it will stop followed with the 2 short beeps.
Unfortunately I cannot do a video which would make it very clear whats going on.

[Kean]

I tried to reproduce this "wiggling" problem in diode mode, but I can't.  Sounds like you have an intermittent internal short.  Strange if you cannot also reproduce in continuity mode.
edit: FW 1.01

[amspire]

By jiggling I mean moving the lead plugs intentionally forward and back "a bit" in their sockets causes the continuous beep to engage with out shorting the probes together. And further to this once the continuous beep has started I can remove the probes from the meter and it carries on beeping until I "wiggle" the selector switch a little bit then it will stop followed with the 2 short beeps.
Unfortunately I cannot do a video which would make it very clear whats going on.

Sounds like you have an intermittent supply of 3V and 15V to the sockets. Could be a poor contact on the switch or a broken trace on the board. Can you connect a voltmeter to the probes and see if the voltage drops when you wiggle?

[lowimpedance]

Okay checking the output with a voltmeter still gives 3 or 15V when continuous beep is going, also when this condition has started the display also goes to all '0' from OFL so no short at the input terminals it would seem.

Just tried a short drop of a few inches height to my desk (no probes) and that can also trigger the continuous beep. This is with no holster BTW.

When the Diode function is not doing the odd behaviour it does measure a diode correctly.

edit: The drop test is not as repeatable as the movement of the probes in the input jacks. I still get the feeling its related to the switch. 
 I will crack it open and take a look tomorrow  to see what movement on the PCB can be induced from the probe jacks.

[amspire]

Okay checking the output with a voltmeter still gives 3 or 15V when continuous beep is going, also when this condition has started the display also goes to all '0' from OFL so no short at the input terminals it would seem.

So it looks like the intermittent connection is somewhere between the measurement IC and the point at which the 3/15v is connected. I still think a switch connection is the most likely cause. You probably should contact Dave directly, unless you want to just Take-It-Apart yourself and have a look.

[maukka]

This was already reported by mattselectronics in the other thread, but the VA mode reports voltage wrong. On 5V range it is too high, on 50V range is much better but a bit too low. Gets worse with higher voltages. Tested with a resistor and a Rigol DP811A with remote sense active. No problems when only measuring voltage, only max 1 digit off. Current is spot on.







EDIT: Did the same test with a Mooshimeter which also has VA (and real power) measurement and it is even more off

Actual measured with a 34401A from DMM terminals: 1.0008V
112GW 1.0133V
Mooshimeter 1.02022V

The Mooshimeter shows 2.0% more than it should, but it is consistent regardless of voltage while on the 112GW error gets larger with increasing voltage.

[maukka]

How much burden voltage do you guys have on the 10A range? Mine is 0.035V/A measured externally while the manual says 0.02V/A. The 112GW itself reports 28.7mV/A.

[EEVblog]

How much burden voltage do you guys have on the 10A range? Mine is 0.035V/A measured externally while the manual says 0.02V/A. The 112GW itself reports 28.7mV/A.

Latest edition of the manual has this revised to 0.03V/A, will upload this when I get back tomorrow.
The previous one didn't include the fuse resistance.

[cpposteve]

Hello mr Jones..!!
Just curious as to when people will get their answers to these on going faults? I’m in the second batch of meters not yet shipped and wondering if all these faults will or most likely be able to be fixed in software?
Hope you had a great holiday.

Steve

[lowimpedance]

 I created a Youtube acc. and uploaded a very short video clip of the Diode test mode continuous beep after giving the probe plugs a wiggle in the meter sockets.
I then removed the probes from the meter to show no external short circuits being the cause and then how a light press on the range switch will stop the tone.

https://youtu.be/rABVuzqzLXQ

I hope this clarifies my earlier posts.

(I will open the meter to investigate this after a weeks holiday)

[Iagash]

I created a Youtube acc. and uploaded a very short video clip of the Diode test mode continuous beep after giving the probe plugs a wiggle in the meter sockets.
I then removed the probes from the meter to show no external short circuits being the cause and then how a light press on the range switch will stop the tone.
(I will open the meter to investigate this after a weeks holiday)

I can confirm this. I also experienced the switch to be unreliable some times.

I fixed it by mounting two small sheets of 0.25mm telson below the snap ring of the switch.

I'll attach a photo.

[1anX]

I created a Youtube acc. and uploaded a very short video clip of the Diode test mode continuous beep after giving the probe plugs a wiggle in the meter sockets.
I then removed the probes from the meter to show no external short circuits being the cause and then how a light press on the range switch will stop the tone.
(I will open the meter to investigate this after a weeks holiday)

I can confirm this. I also experienced the switch to be unreliable some times.

I fixed it by mounting two small sheets of 0.25mm telson below the snap ring of the switch.

I'll attach a photo.

Hmmm, looks like it requires some form of spring/wave washer type tension device included. Case may not be rigid enough to provide consistent tension for the contacts without a simple spring tension device being fitted!

Wave washer info here http://www.globalspec.com/learnmore/mechanical_components/springs/wave_washers

That's not a good indicator for the construction robustness of the meter and hopefully a simple mechanical fix will be found. Well documented and fixed Iagash, we all benefit from your faulty switch investigation.

[EEVblog]

I can confirm this. I also experienced the switch to be unreliable some times.
I fixed it by mounting two small sheets of 0.25mm telson below the snap ring of the switch.
I'll attach a photo.

I do not understand this.
That fix is on the case of the meter, not on the carrier that holds the switch contacts which is a different assembly mounted and clipped to the PCB that has it's own tension with the plastic insert clip.

[EEVblog]

Hello mr Jones..!!
Just curious as to when people will get their answers to these on going faults?

When I know, you'll know.

[Iagash]

I can confirm this. I also experienced the switch to be unreliable some times.
I fixed it by mounting two small sheets of 0.25mm telson below the snap ring of the switch.
I'll attach a photo.

I do not understand this.
That fix is on the case of the meter, not on the carrier that holds the switch contacts which is a different assembly mounted and clipped to the PCB that has it's own tension with the plastic insert clip.

Yes, but the effect is the same. The range switch is pressed a little more to the pcb by the clip ring. With this washer the plastic insert clip is relieved. It seemed easier that way as you can see in the video poking the range switch makes the meter switch the mode. When poking the range switch from the top, you also apply pressure via the clip ring to the switch and move it a bit more to the pcb.

Edit:
Since there are only very little reports here about the switch, it might be a tolerance issue which only affects a minority of meters.

[amspire]

I think the switch problem may be due to two things:

• The fact the selector knob wobbles much more then other multimeters I have seen - even the $10 ones
• If you push the knob down, the clip ring pushes down on the switch. Not sure that should happen

The wobble in the knob is wobbling the switch on the PCB from side to side. Probably not good if you want to maintain the tension in the spring contacts in the switch.

The looseness of the clip spring combined with the tapers of both the knob and the case knob recess all combine to allow for this wobble. If the knob was moulded with a reverse taper so it is wider at the top then the bottom, it could have a far more snug fit and would be less affected by any clip ring looseness.

As an experiment, I added a spacer between the knob and the nylon detent spring to raise the knob so that the clip ring groove was just above the inner case plastic, but the clip ring was not tight against the plastic. This is different from the approach Iagash took. I also added a couple of layers of Kapton tape around the outside of the knob to stop the wobble a little. It now seems that pressing on the knob never depresses the switch, and the wobble is much less. I think the switch has a better feel now.

Basically what I am saying is if the knob moulding was tweaked a bit, the switch could possible be more reliable and feel much more solid. It is just out here and there by fractions of a millimetre and that is all it takes.

Don't know what the best advice is for people with contact issues. I would probably want to inspect the contacts to see if any had been deformed a little. You should not need to have the clip ring pushing the switch down by perhaps 0.1mm. That does not feel like a real solution.

[lowimpedance]

I should emphasize that the diode tone issue I have starts from the probe movement
In their sockets and not from switch movement. But once started both probe and gentle
pressure on the switch will stop it, as shown in the short video.
BTW it was too hard to video and show wiggled that probes (mobile phone in one hand).

[EEVblog]

Basically what I am saying is if the knob moulding was tweaked a bit, the switch could possible be more reliable and feel much more solid. It is just out here and there by fractions of a millimetre and that is all it takes.

Switch wobble confirmed on the two remaining meters we have here.
We (as in David2 + me) also suspect it's some slight difference in production tooling process, although the pre-production was obviously supposed to be the same.
The pre-production units were fine.

REMINDER, please keep discussions in the discussion thread:
https://www.eevblog.com/forum/testgear/eevblog-121gw-discussion-thread/

[3db]

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 ?