Author Topic: EEVblog 121GW Multimeter Issues  (Read 193223 times)

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Offline DavidDLC

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Re: EEVblog 121GW Multimeter Issues
« Reply #700 on: September 25, 2018, 05:39:49 pm »
There has to be a sanity check every time a new firmware is released.

A huge checklist testing mainly every possible scenario.

David DLC
 

Offline CDaniel

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Re: EEVblog 121GW Multimeter Issues
« Reply #701 on: September 25, 2018, 05:57:18 pm »
Ok , but when I insert the probes those values go to almost zero , this wasn't happening before in my case even with shorted leads. Maybe has something to do with input warning circuit leaking some DC back if you look at schematic ... and was corrected by adding some offsets in firmware .
« Last Edit: September 25, 2018, 06:12:27 pm by CDaniel »
 

Offline DavidDLC

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Re: EEVblog 121GW Multimeter Issues
« Reply #702 on: September 25, 2018, 06:11:02 pm »
I recall when I connect and short the leads, still showing 0.3.

On any case, you should not have to do anything for the meter to show 0.

Do not accept or justify anything that is not good quality

David DLC
 

Offline IanB

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Re: EEVblog 121GW Multimeter Issues
« Reply #703 on: September 26, 2018, 05:41:56 pm »
I wonder if this could have any connection with the spikes I have observed?

The difference is that the spikes I have seen are very frequent, and they are visible on the meter's LCD display. They also happen whether or not the BT interface is enabled.
I'm not an EE--what am I doing here?
 

Offline Lion_Tamer

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Re: EEVblog 121GW Multimeter Issues
« Reply #704 on: September 27, 2018, 08:48:55 pm »
I have been looking at the packet protocol document but as it seems to be missing a fair bit of information (It may be me not be reading it correctly) I decided to start making my own but as I don't have a blue tooth adapter on the PC I have been probing the UART interface to the BLE112 inside the meter with my logic analyser and have noticed a couple of quirks.

1. The Year value of the packet never changes no matter what is set on the meter.
2. The Month value of the packet never changes no matter what is set on the meter.
3. While decoding the Main LCD Range packet (7) I noticed that on AC and DC micro Watts the 2500.0uVA range appears to be repeated - this shows on both the meter display and the UART packet.

I am using V1.51 on my meter.

Jem
 

Offline Seppy

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Re: EEVblog 121GW Multimeter Issues
« Reply #705 on: September 28, 2018, 12:08:54 am »
I have been looking at the packet protocol document but as it seems to be missing a fair bit of information (It may be me not be reading it correctly) I decided to start making my own but as I don't have a blue tooth adapter on the PC I have been probing the UART interface to the BLE112 inside the meter with my logic analyser and have noticed a couple of quirks.

1. The Year value of the packet never changes no matter what is set on the meter.
2. The Month value of the packet never changes no matter what is set on the meter.
3. While decoding the Main LCD Range packet (7) I noticed that on AC and DC micro Watts the 2500.0uVA range appears to be repeated - this shows on both the meter display and the UART packet.

I am using V1.51 on my meter.

Jem

Have a look at the code example for the packet in the packet document, it might assist in your understanding of the packet.
The document currently doesn't have outgoing packets.

1.
Are you referring to the serial number as the date?

2.
^

3.
Edit, I had wrong branch before:
You can look at the source for the packet processing in the app here:
https://gitlab.com/Sepps/app-121gw/blob/PrivatePostRelease/121GW.Core/Controls/Multimeter/Packet121GW.cs

Older branches used different reject criteria for the packets, this one checks length and checksum only.
Please also ensure you have the latest firmware as the packet document V2 refers to the latest versions of the firmware only.
« Last Edit: September 28, 2018, 02:47:06 am by Seppy »
 

Offline GeoffreyF

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Re: EEVblog 121GW Multimeter Issues
« Reply #706 on: September 28, 2018, 01:21:18 am »
It was posted earlier about the battery springs.  At that time, I saw no problem but now, updating to 1.51, had an almost scary moment.  I did the update with the battery cover off. All went well but then the battery cover was not quite all the way on, as I reinstalled it.   I removed it again and noticed that one of the batteries had partly popped out, but the spring was still contacting.  Had the battery fully dislodged during the update, that might have been a bad thing.

So - I think it's best to replace the battery cover fully before starting the update.  That's the safest thing.

I also suggest that this caution be added to the manual under firmware update.  "Replace Battery cover before update to prevent interruption if battery pops out".
US Amateur Extra W1GCF.
 

Offline GeoffreyF

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Re: EEVblog 121GW Multimeter Issues
« Reply #707 on: September 28, 2018, 01:34:32 am »
I think that when the upload of an EEVBlog.bin file is complete, it should be deleted.  This would free up that space for meter logging functions.  I can't think of a reason why to keep it there once the upload is done.  A user would not have to go back into the meter to delete the file, assuming they are OCD about that.  Then - as I prior recommended, the battery door can be screwed down before an upload is started.
US Amateur Extra W1GCF.
 

Offline JS

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Re: EEVblog 121GW Multimeter Issues
« Reply #708 on: September 28, 2018, 01:58:22 am »
I think that when the upload of an EEVBlog.bin file is complete, it should be deleted.  This would free up that space for meter logging functions.  I can't think of a reason why to keep it there once the upload is done.  A user would not have to go back into the meter to delete the file, assuming they are OCD about that.  Then - as I prior recommended, the battery door can be screwed down before an upload is started.
Seriously? How much does the bin file weights? How much time for logging it is? And compare that with the 8GB the SD has... If you record that much data will need to be in many separate batches as the batteries won't last that long, then you have the problem with the naming and k owong which is which...

I save a few bins so I just need to rename if I want to change it, I've been going back and forth a few times from V1.26 to V1.00. For me it would be much cooler being able to select the fw versions from many in the SD without needing to remove it and change the name. Note that some versions are noisier while others are faster, among other differences between them, like features and bug corrections.

JS

If I don't know how it works, I prefer not to turn it on.
 
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Offline darik

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Re: EEVblog 121GW Multimeter Issues
« Reply #709 on: September 28, 2018, 09:06:15 pm »
What ever is causing the communications to slow down appears to be the 121GW's main firmware.

Do you know it's not something going on in the Bluetooth protocol? It's probably doing it's own error checking and 2.4 GHz band is crowded with interference. It could be getting backed up with retransmissions or something. It's wireless, it cannot be trusted.
 

Offline bicycleguy

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Re: EEVblog 121GW Multimeter Issues
« Reply #710 on: September 29, 2018, 03:16:32 am »
...
Your having so much fun with the new 121GW !!    and so persistent :-+

I was going to try something but maybe you want to.  I think your getting close in your tests.

1. Hook up a SPI interface to the SD card pins and time the intervals of writing to the card.
2. While doing 1 put a signal generators output at a DC + slowly swept frequency in to the meter to make the pauses show while it hunts.
3. After doing this you can test how it relates to the bluetooth.


Have fun ;)
 

Offline firewalker

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Re: EEVblog 121GW Multimeter Issues
« Reply #711 on: September 29, 2018, 03:46:10 pm »
Probably answered before. But... are those Matlab programs available for download yet?

Alexander.
Become a realist, stay a dreamer.

 

Offline bicycleguy

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Re: EEVblog 121GW Multimeter Issues
« Reply #712 on: September 29, 2018, 04:33:21 pm »
...
As a side note, I had changed the meter to Eneloop NiMH and had never charged it. The battery indicator never came on.  Even after all of this testing.   Finally it gave up last night.  ...

I think the 4.2V at which the meter assumes your going to replace the batterys is great for replacement but to low for NIMH if you want them to last.  Numerous references suggest 1.1V minimum cell voltage.  However, here's a typical quote, this one from Wikipedia:

 "Complete discharge of multi-cell packs can cause reverse polarity in one or more cells, which can permanently damage them. This situation can occur in the common arrangement of four AA cells in series in a digital camera, where one completely discharges before the others due to small differences in capacity among the cells. When this happens, the good cells start to drive the discharged cell into reverse polarity (i.e. positive anode/negative cathode)."

I use 5.0V on the bat display and still get plenty of life.  I have only re-charged the 2 to 3 year old batteries once since acquiring the meter and many days of logging.  At the current firmware revision rate, that's about one charge every 3 revisions. ^-^
 

Offline Seppy

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Re: EEVblog 121GW Multimeter Issues
« Reply #713 on: October 03, 2018, 01:48:53 am »
It appears by the time version 10.0 rolled out, they had converted to a 19 byte, binary format.  It's very similar to what we have today.   They were still running at 250ms.   It looks like the firmware, even with only 30% of the amount of data that had been sent, it was already starting to lag.   

Firmware Version -  Format, #Bytes in packet, Packet Rate, Timing Stable or does it lag

1.00 - ASCII, 56 Bytes, 250ms, Stable
1.05 - ASCII, 56 Bytes, 250ms, Stable
1.07 - ASCII, 56 Bytes, 250ms, Stable
1.10 - Binary, 19 Bytes, 250ms, Lags

Corrected version numbers

Do you have some details about the test you performed, I'm writing a bug report but not really sure specifically what you've done. By lag do you mean the time between logging and the actual signal or the the sample rate is slower than expected slightly?
 

Offline Seppy

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Re: EEVblog 121GW Multimeter Issues
« Reply #714 on: October 03, 2018, 03:21:34 am »
It appears by the time version 10.0 rolled out, they had converted to a 19 byte, binary format.  It's very similar to what we have today.   They were still running at 250ms.   It looks like the firmware, even with only 30% of the amount of data that had been sent, it was already starting to lag.   

Firmware Version -  Format, #Bytes in packet, Packet Rate, Timing Stable or does it lag

1.00 - ASCII, 56 Bytes, 250ms, Stable
1.05 - ASCII, 56 Bytes, 250ms, Stable
1.07 - ASCII, 56 Bytes, 250ms, Stable
1.10 - Binary, 19 Bytes, 250ms, Lags

Corrected version numbers

Do you have some details about the test you performed, I'm writing a bug report but not really sure specifically what you've done. By lag do you mean the time between logging and the actual signal or the the sample rate is slower than expected slightly?

Forget the RF link for now.  Just monitor the serial lines from the meter's MCU.  You will find that the rate that the packets are sent will vary depending on the input signal.  Depending on the version of firmware you install, the time between packets will be 500ms or 250ms.  I have shown where this time can be seconds.   This does not appear to be a problem with the older firmware.   It appears the problem showed up in version 1.10 when the packet sized was reduced and the binary format was introduced. 

I suspect the packet rate was slowed down even further after 1.10 in an attempt to resolve the lag between packets.  However, in 1.00, they were sending almost 3X more data at the 250ms rate and not lagging. 

I would think they could write the newer binary formatted, smaller packet like 1.51 uses at the same rate they write to the SD card and not lag.

I'll look into this for you, I think we will be able to work it out.
Just so I don't have to redo your test (will be faster), do you have examples of the sampled UART data that show this (a screen shot or photo of the logic analyzer)? Something that shows the jitter between samples.

If you don't see this before 4pm I'll do the test myself but I figured I'd ask.
« Last Edit: October 03, 2018, 03:24:55 am by Seppy »
 

Offline Dr. Frank

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EEVblog 121GW Multimeter Issues
« Reply #715 on: October 03, 2018, 04:31:05 pm »

Yes, I confirm these values of 0.022µA and 0.32mA @ FW 1.51.
With FW 1.26, it's 0.046µA and 0.06mA, though.

Maybe there's a systematic bug inside these modes.
Change was 'Amp range sensitivity improved'.. probably that causes this offset.

Frank

[Adder]: It makes no difference, whether probes are inserted, or not.

Loading the new FW 1.51 simply affected the zero calibration of the DCI ranges:

               1.26          1.51
50µA      -0.055       0.017
500µA     0.14        -0.07
5mA      -0.0015      0.0027
50mA     0.001       -0.020
500mA  -0.12         0.25
5A        -0.0001     -0.0021
10A       0.000       -0.001

I have re-calibrated only the zero offset of ranges 50µA .. 5A, so now all ranges have a few counts offset.
That did not influence the gain calibration, as far as I could tell.

Frank

« Last Edit: October 03, 2018, 04:32:44 pm by Dr. Frank »
 

Offline Seppy

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Re: EEVblog 121GW Multimeter Issues
« Reply #716 on: October 04, 2018, 12:34:46 am »
I'll look into this for you, I think we will be able to work it out.
Just so I don't have to redo your test (will be faster), do you have examples of the sampled UART data that show this (a screen shot or photo of the logic analyzer)? Something that shows the jitter between samples.

If you don't see this before 4pm I'll do the test myself but I figured I'd ask.

There are several posted on this thread.  If you look at this picture for example, there are two different programs shown.  The one in the upper left is using a FTDI TTL to USB adapter to sniff the serial line from the MCU.   In this case, I am counting the number of times the the time between packets is longer than 800ms.   The main program is looking at the data across the RF link.  The yellow trace is also the number of times the packet spacing has exceeded 800ms.  Note how the two track.  Als note that the blue trace, showing the CRC failure rate is not effected.   

It you would rather see the actual time, TEST2E is showing just that using different modes and signals applied.  Again, in the 5V range with nothing attached to the meter, so the readout is basically all zeros, the packet spacing is very repeatable.   

You could use a LA but I was wanting to capture more metrics.   Actually, you could add some checks to your Windows application and check it on the RF receiver side like I was originally doing.   Should be easy enough to replicate. 


****

On TEST2E, the vertical axis is time in ms.

Alright I was able to reproduce this a fix will come some time soon.
But that is at the discretion of UEi.
« Last Edit: October 04, 2018, 02:05:50 am by Seppy »
 

Offline CDaniel

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Re: EEVblog 121GW Multimeter Issues
« Reply #717 on: October 04, 2018, 05:21:03 pm »
Did you noticed that in diode mode when shorting probes the beeping sound is very slow responding ? I must hold the short for about 0,5sec  :P 
« Last Edit: October 04, 2018, 05:23:53 pm by CDaniel »
 

Offline chronos42

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Re: EEVblog 121GW Multimeter Issues
« Reply #718 on: October 04, 2018, 06:13:00 pm »
Hi,

I have tried to calibrate out the high offset in the current  mode in firmware 1.51, but that seems impossible because of a lack of information or a hardware issue. (Or I am simply to stupid)

I first tried to calibrate the offset in the µA range.

No cable plugged in the mAµA binding post : -0.028µA
Cable plugged in: 0.015 µA. I assume that has to do with the cable sensor.
Cable plugged in and shorted to COM: 0.030µA

In the A/mA Range: No Cable plugged in: 0.23mA offset.
In this case the meter uses the A 500mA binding post. This connector seems not critical and is the only range that can be calibrated out without problems.
Cable plugged in the mAµA binding post: 0.0025mA
Shorted to COM: 0.0006 mA after a long settling time.
Any hints how to proceed best?
No cable plugged in?
With cable plugged in?
With cable plugged in and shorted to COM?  :scared:
« Last Edit: October 04, 2018, 08:38:57 pm by chronos42 »
 

Offline OldEE

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Re: EEVblog 121GW Multimeter Issues
« Reply #719 on: October 05, 2018, 01:45:02 am »
I'm wondering how many of you are seeing the offset on DC current ranges?

For example my 10 day old 121GW, on the 500mA range, has about a 0.2 mA positive offset.  Like Dr. Frank I'm likely going to do the offset calibration.  My concern is that the offset varies over time.  I've seen it as low as 0.07 mA and as high as 0.28 mA on the 500 mA range. 

The offsets were about the same for the as shipped 1.22 firmware and the 1.51 firmware so no issue there or on DCV or any AC modes.  As of now the offsets for the 5, 50, 500 mA ranges are 0.0016, -0.0019, 0.19 and the 5 A and 10 A ranges are -0.0018 A and -0.001 respectively.

Below is about 5 hours of logging at 10 per hour on the 500 mA range.  You can see the randomness.  The room temperature varied about 1.5C over the 5 hours.  The first reading is anomalous (is that a bug?).  No leads were connected per the calibration table except for one open lead in the mA/uA jack to activate the 5 and 50 mA range.

START,2018/10/03,22:53:01,
ID,170800000,
INTERVAL,300,sec,
,MAIN,,,SUB-1,,,SUB-2,,,Remark,
No. ,Func. ,Value,Unit,Func. ,Value,Unit,Func. ,Value,Unit,
1,DCA,-0003.51,mA,,,,,,,,
2,DCA,0000.24,mA,,,,,,,,
3,DCA,0000.19,mA,,,,,,,,
4,DCA,0000.16,mA,,,,,,,,
5,DCA,0000.22,mA,,,,,,,,
6,DCA,0000.18,mA,,,,,,,,
7,DCA,0000.17,mA,,,,,,,,
8,DCA,0000.17,mA,,,,,,,,
9,DCA,0000.19,mA,,,,,,,,
10,DCA,0000.16,mA,,,,,,,,
11,DCA,0000.20,mA,,,,,,,,
12,DCA,0000.16,mA,,,,,,,,
13,DCA,0000.18,mA,,,,,,,,
14,DCA,0000.18,mA,,,,,,,,
15,DCA,0000.18,mA,,,,,,,,
16,DCA,0000.19,mA,,,,,,,,
17,DCA,0000.19,mA,,,,,,,,
18,DCA,0000.20,mA,,,,,,,,
19,DCA,0000.24,mA,,,,,,,,
20,DCA,0000.22,mA,,,,,,,,
21,DCA,0000.14,mA,,,,,,,,
22,DCA,0000.19,mA,,,,,,,,
23,DCA,0000.19,mA,,,,,,,,
24,DCA,0000.26,mA,,,,,,,,
25,DCA,0000.13,mA,,,,,,,,
26,DCA,0000.22,mA,,,,,,,,
27,DCA,0000.26,mA,,,,,,,,
28,DCA,0000.15,mA,,,,,,,,
29,DCA,0000.23,mA,,,,,,,,
30,DCA,0000.22,mA,,,,,,,,
31,DCA,0000.19,mA,,,,,,,,
32,DCA,0000.22,mA,,,,,,,,
33,DCA,0000.22,mA,,,,,,,,
34,DCA,0000.18,mA,,,,,,,,
35,DCA,0000.25,mA,,,,,,,,
36,DCA,0000.21,mA,,,,,,,,
37,DCA,0000.23,mA,,,,,,,,
38,DCA,0000.25,mA,,,,,,,,
39,DCA,0000.15,mA,,,,,,,,
40,DCA,0000.20,mA,,,,,,,,
41,DCA,0000.15,mA,,,,,,,,
42,DCA,0000.14,mA,,,,,,,,
43,DCA,0000.26,mA,,,,,,,,
44,DCA,0000.22,mA,,,,,,,,
45,DCA,0000.21,mA,,,,,,,,
46,DCA,0000.23,mA,,,,,,,,
47,DCA,0000.20,mA,,,,,,,,
48,DCA,0000.17,mA,,,,,,,,
49,DCA,0000.18,mA,,,,,,,,
50,DCA,0000.28,mA,,,,,,,,
51,DCA,0000.26,mA,,,,,,,,
52,DCA,0000.20,mA,,,,,,,,
53,DCA,0000.23,mA,,,,,,,,
54,DCA,0000.26,mA,,,,,,,,
55,DCA,0000.24,mA,,,,,,,,
56,DCA,0000.22,mA,,,,,,,,
57,DCA,0000.21,mA,,,,,,,,
58,DCA,0000.21,mA,,,,,,,,
MAX,50,DCA,0000.28,mA,
MIN,1,DCA,-0003.51,mA,
« Last Edit: October 05, 2018, 01:55:59 am by OldEE »
 

Offline Seppy

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Re: EEVblog 121GW Multimeter Issues
« Reply #720 on: October 05, 2018, 02:59:11 am »
Very nice.  Thanks for taking the time to dig into it. 

I am playing around with a UNI-T meter using BLE as well.  There is still a lot of work to do on it but there are some things that UNI-T does that UEI could leverage.  One major difference is how the display data is sent.  The 121GW has the data, sign bit, scaling...  The UNI-T sends the data as a float.  IMO this is much easier on the PC side of things. 

They also embed a checksum and like the 121GW, it seems to be required but the error rate is much lower for what ever reason.    They can update at 10Hz rather than 2Hz and are sending 55 Bytes.  If anything, I would expect the CRC error rate to be higher on the UNI-T. 

https://www.eevblog.com/forum/projects/uni-t-ut-d07a-bluetooth/

Hello Joe,

Does this resolve sampling rate the issue for you?
Not an official released version yet. I figured you'd appreciate the update asap.

https://www.eevblog.com/wp-content/uploads/2017/11/EEVBlog1_52.zip
 

Offline chronos42

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Re: EEVblog 121GW Multimeter Issues
« Reply #721 on: October 05, 2018, 08:51:21 am »
Hi,

I tried out how to calibrate the DC current offset  and made a short instruction how to proceed.


1: Backup your calibration data! (See page 66 in the manual)
2: Copy the backup from the SD card also to your PC, because one wrong keypress and you overwrite your CAL backup inadvertently at the SD card.
3: Remove all leads from the meter.
4: Switch off the meter.
5: Hold MODE and turn on the meter.
6: Release MODE and press REL immediately
7: Set the meter to A mA , press SETUP and wait
8: Press RANGE, press SETUP and wait
9: Plug in a lead in binding post mAµA
10: Press SETUP and wait
11: Press RANGE, press SETUP and wait
12:  Switch to µA, cable is still plugged in the mAµA binding post
13: Press SETUP and wait
14: Press RANGE, press SETUP and wait
15: Press MEM until CAL dissapears for short time, then switch off the meter.

In case that somthing went wrong restore your saved CAL data.

I found that the offset is not really stable, after some time it is again 4..5 digits off. But still much better than before the calibration.

Update: Add some more steps.
« Last Edit: October 05, 2018, 05:55:49 pm by chronos42 »
 
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Offline CDaniel

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Re: EEVblog 121GW Multimeter Issues
« Reply #722 on: October 06, 2018, 11:41:49 am »
Current mode uses an electronic switch and the x10 operational amplifier on some ranges , it is not like DC volts circuit . If you don't measure anything , is somewhat normal to have some drifting over time because of induced noise which is not constant , the same if you move the probes and the multimeter .
This test should be done with a precision current source , measuring some real currents.
« Last Edit: October 06, 2018, 12:12:20 pm by CDaniel »
 

Offline chronos42

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Re: EEVblog 121GW Multimeter Issues
« Reply #723 on: October 06, 2018, 01:28:37 pm »
Every mode uses electronic switches and operational amplifiers, so that is not the reason for the offset behavior in the ampere mode. I suspect that the reason is mostly a problem with thermo voltages in the junctions of the shunt resistors that are amplified also.
The low burden voltage has the advantage that it has a low voltage drop. But the disadvantage is a higher and unstable offset. That may be the reason that no other provider offers a low burden voltage multimeter. The disadvantages seems greater for them than the lower burden voltage.

I did tests with a precision current source and the offsets were still there. And yes, mostly the meter is within its specs, but these specs are at a low level with 0.75% + 15 counts. It is much better after recalibrating the offsets in the ampere mode. (Tested with a Knick JS 3010 voltage/current calibrator)
« Last Edit: October 06, 2018, 01:51:09 pm by chronos42 »
 

Offline Seppy

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Re: EEVblog 121GW Multimeter Issues
« Reply #724 on: October 10, 2018, 02:19:49 am »
I was a little confused about what I was seeing when I was attempting to write a Labview app for the 121.  Looking deeper into the BLE interface, if you fire up Wireshark you will find that the 121 sends a single packet for the start byte.  It's a bit odd as the entire data structure could fit into a single packet but the 121 will send two.     I suspect this may have been a carry over from the earlier structure.   

It's too bad that the BLE112's serial interface was not routed to the MCU so you could field upgrade it with the firmware.   It looks like you are stuck with what you have unless there is a newer release of the meter at some point.

Indeed, we discovered this too. It is indeed a carry over from when the structure was much larger.
What version of the firmware are you using?
 


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