EEVblog 121GW Multimeter Issues

[Scottjd]

What's the open circuit HV diode test putting out now?

17.332V

That's interesting.  I think the prototype was under 17.   I was a bit concerned with the mux they were using had an absolute max rating.  It looked like they stayed with the same part in Dave's close up video showing the board.   Maybe they came up with a better way to protect it.   From what I saw, the mux was the weak point as far as the transient tests I run.    That mux is an HEFxxxx  located near the edge of the PCB if you wanted to pull the datasheets to have a look.   I think its an absolute max of 18 on that one.  You can drive it a little above the rail.   Easy enough to trace the path to the input pin to see how it is being protected.   Again, hard to say if you would call it a bug or issue anyway.  Maybe just something to be aware of.   

Good question, it was claimed to be 15V, so if it has the room maybe a good TVS diode could go in and even with the voltage drop it would still be above 15V. But I don’t know if a TVS diode would even stop your transients Joe. But it would be better then nothing.

[dr.diesel]

What's the open circuit HV diode test putting out now?

17.332V

000063 = 16.3V
000061 = 17.8V

[mikeselectricstuff]

What's the open circuit HV diode test putting out now?

17.332V

000063 = 16.3V
000061 = 17.8V

Is it significantly dependent on battery voltage ?

[dr.diesel]

Bug, FW 1.01.

Switching to diode test mode, the secondary display continues to show temp, not 3/15v like it should, until the Range button is cycled.

[dr.diesel]

What's the open circuit HV diode test putting out now?

17.332V

000063 = 16.3V
000061 = 17.8V

Is it significantly dependent on battery voltage ?

From 5-6.5V battery voltage has no impact.

[hwti]

What's the open circuit HV diode test putting out now?

17.332V

Here 15.45V (and 3.23V for the 3V mode), FW 1.02

[hwti]

• The range switch is unreliable, you sometimes need to poke it a bit until the meter behaves properly.
• The inability to disable the excessive beeping or at least lowering the volume get's annoying fast.
• Autoranging speed in Ohms is way too slow.

I just had the range switch issue : after switching from V to Low-Z, it stayed in volts mode, I had to move the switch a little bit.

+1 for the annoying beeps and slow autoranging

[lewis]

Beep beep. Beep. Beep. Beep. Beep!

FOR THE LOVE OF GOD....

Skip to 6min 32sec

[joeqsmith]

What's the open circuit HV diode test putting out now?

17.332V

That's interesting.  I think the prototype was under 17.   I was a bit concerned with the mux they were using had an absolute max rating.  It looked like they stayed with the same part in Dave's close up video showing the board.   Maybe they came up with a better way to protect it.   From what I saw, the mux was the weak point as far as the transient tests I run.    That mux is an HEFxxxx  located near the edge of the PCB if you wanted to pull the datasheets to have a look.   I think its an absolute max of 18 on that one.  You can drive it a little above the rail.   Easy enough to trace the path to the input pin to see how it is being protected.   Again, hard to say if you would call it a bug or issue anyway.  Maybe just something to be aware of.   

Good question, it was claimed to be 15V, so if it has the room maybe a good TVS diode could go in and even with the voltage drop it would still be above 15V. But I don’t know if a TVS diode would even stop your transients Joe. But it would be better then nothing.

I assume 15 would be the minimum.  It really would not matter to me anyway, if it ran a little hot (higher).  Actually, I would prefer it.   It the part has an absolute max of 18 and they are running it a bit over 17, there is not a lot of wiggle room.  You don't want it to leak and you don't ever want to exceed that absolute value.   I don't know if they made improvements to the released meter or not and am only assuming it's the same based on the comments.   They may have found a better way to protect it.   

There was a third video of my final mods as well. I damaged that prototype a few times before settling in on part selection.  I don't remember how high I went up to with it before calling it good enough.  I can tell you I never put the grim reaper on it with 14KV or bust.          

[ChrisG]

Received mine on 12th Jan in Netherlands. Auto ranging is ridicuously slow. None of my other DMM’s 869, 235 and an old Metrixc 53c are so slow. Is this an issue or by design?

Apologies.  Just noticed it has been mentioned already many times. V 1.02 is my firmware. Will do more tests later.

[mikeselectricstuff]

Has anyone checked to see if they still limit the frequency counter to 1MHz?   Again, not really a bug perhaps but more a slight oversight.

Or maybe there are issues like jitter or miscounts that make higher frequencies subject to errors?

[hwti]

Has anyone checked to see if they still limit the frequency counter to 1MHz?   Again, not really a bug perhaps but more a slight oversight.

It's still limited.
It's in the manual : "99.999 Hz to 999.99 kHz" ranges.

[The Soulman]

NOTE: Can we please limit this thread to reporting and confirmation of bugs and issues, any discussions should be on the discussion thread.
Thanks.

[Scottjd]

NOTE: Can we please limit this thread to reporting and confirmation of bugs and issues, any discussions should be on the discussion thread.
Thanks.

I didn’t know we were keeping score.
One point to you!
Who is winning?

Wait, that’s your signature, not your post. That doesn’t count then.
So if this is the bugs only (some know about before the release and never fixed?) the What thread is the shipping only? Does anyone know, I tried searching but their is so many threaded mentioning the 121GW in then. Most old threads before the Kickstarter even launched.

[The Soulman]

Well maybe this one is actually monitored by Dave and he gets a notification for every single reply here so he can gather data
to form statistics and eventually can act accordingly?
Don't pollute it.

[1anX]

For those looking for another place to post, there is a discussion thread up and running on the meter here!
https://www.eevblog.com/forum/testgear/eevblog-121gw-discussion-thread/

[Kal]

I can aslo confirm that v1.02 autoranging is very slow, especially measuring low ohms or higher voltages. Compared to BM235 its about 16 times slower worst case (0.5s vs 8s, short circuit measurement) which makes those modes basically unusable at the moment. I'm expecting this should be easily fixable in firmware so not too worried, just looks like it's always measuring at full precision starting from Mohms range and not doing fast range checking measurments at first.

[idpromnut]

@Dave: when you get the chance, can you see about getting the firmware update v1.02 published for those of us that have only v1.01?  Thanks!

[nuclearcat]

BLE data corruption issue:

Code: [Select]

#!/usr/bin/python
from bluepy import btle
from bluepy.btle import UUID, Peripheral,DefaultDelegate
import binascii
import array
from struct import *

def parse_data(x):
    xlen = len(x)
    for offset in range(0,xlen):
        if (ord(x[offset:offset+1]) == 0xF2):
            # Process accumulated data
            print ("Accumulated data(%d): %s" % (len(parse_data.accumulated_data), str(parse_data.accumulated_data)))
            parse_data.accumulated_data = array.array('c')
        else:
            parse_data.accumulated_data.append(x[offset:offset+1])

class MyDelegate(btle.DefaultDelegate):
    def __init__(self):
        btle.DefaultDelegate.__init__(self)

    def handleNotification(self, cHandle, data):
         parse_data(data)


parse_data.accumulated_data = array.array('c')
# Put your multimeter mac here
p = btle.Peripheral("88:6B:XX:XX:XX:XX", btle.ADDR_TYPE_PUBLIC)
p.setDelegate( MyDelegate() )

print('Ready!')
p.writeCharacteristic(0x9, "\x03\x00")

while True:
    if p.waitForNotifications(1.0):
        continue

    print("Waiting...")

with this script it is easy to reproduce data corruption over BLE, length is changing and bits are flipping.
For example:

Code: [Select]

31373038303030303030313031343041451b34303130304537303130383038343030303030300a
3137303830303030303031300c343041453634303130304537303130383038343030303030300a
31373038303030303030313031343041453634303130304537303130383038343030303030300a
31373038303030303030313031343041453634303130304537303130383038343030303030300a
31373038303030303030313031343041453607303834303030303030303030303030303030300a
31373038303030303030313031343041450d74373031303830383430303030303030303030300a
3137303830303030303031303134304145360a
31370638303030303030313031343041453634303130304537303130383038343030303030300a <-- here is a "06" at pos 5,6 where I expected "30"
31373038303030303030313031343041453634303130304537303106383038343030303030300a
31373038303030303030313031343041453634303130534537303130383038343030303030300a
31373038303030303030313031343041453634303130304537303130383038343030303030300a
3137303830303030303031303134304145360c304537303130383038343030303030303030300a
3137303830303030303031303134304145360630303030303030303030303032440d0a
313730383030303030303130313430414536343031300a
31373038303030303030313031343041453634303130304537303130383038343030303030300a
31373038303030303030313031343041453634300330304537303130383038343030303030300a
31373038303030303030313031343041453634303130304537303130383038343030303030300a
31373038303030303030313031343041453634303130304537303130383038343030303030300a
31373038303030303030313031343041453634303130304537303130383038343030303030300a
31373038303030303030313031343041453681303030303030303030303030303030303030300a
313730383030303030303130313430414536303032440d0a
3137303830303030303031303134304145363430313030453730313038303834300a
31373038303030303030313031343041453634303130304537303130383038343030303030300a
31373038303030303030313031343041453634303130304537303130383038341830303030300a


[IanB]

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.

[fanOfeeDIY]

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.
Attached is the screen shot when opening the log file with binary editor.
0x00 is not in ASCII code.

This is my pure guess based on my software engineering experience. The firmware is trying to write the data to SD card however it could be it has memory writing over flow, memory leak or improper locking between other threads.

[iainwhite]

My issues:

1. The manual is not very clear on the type of Setup button press that is needed e.g. long press to save a value after editing it.
2. The constant beeping is driving me mad. Please can we have an option to turn off the beeper.

I realize that both these issues have already been reported.

[EEVblog]

Seems like YOU are the one polluting it.  Have anything technical to add?

I'll be very clear again.
This thread is for REPORTS of bugs and issues and CONFIRMATIONS of those bugs and issues.
DO NOT discuss them here, PLEASE!

[amspire]

Addition to Dec 11th Manual:

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 gather it is a programmable Serial number or ID number used in Bluetooth communication to identify a meter.

[joeqsmith]

Seems like YOU are the one polluting it.  Have anything technical to add?

I'll be very clear again.
This thread is for REPORTS of bugs and issues and CONFIRMATIONS of those bugs and issues.
DO NOT discuss them here, PLEASE!

I did not realize you were censoring posts in this area.   I resubmitted the post you removed twice because I literally thought I had forgotten to press the send key, not because I was trying to be a dick about it.