Author Topic: EEVblog 121GW Multimeter Issues  (Read 195042 times)

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Offline Seppy

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Re: EEVblog 121GW Multimeter Issues
« Reply #725 on: October 10, 2018, 03:04:52 am »
I am back to 1.26 with the BLE112 image that was uploaded.   

Did you try to see if you could still replicate the lag with the beta firmware like I showed?


In your image you have a note that says, "see page 66 of API" what do you mean?
I haven't yet, the plan was for tomorrow morning, I'm doing a few tests at once.
« Last Edit: October 10, 2018, 03:07:48 am by Seppy »
 

Offline eV1Te

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Re: EEVblog 121GW Multimeter Issues
« Reply #726 on: October 10, 2018, 06:08:43 pm »
I am seeing very large offset voltages (up to several mV) in mV range after having measured larger voltages some minutes earlier. Offset voltage recovers slowly over the course of some 30 minutes, until it is a few uV. But in that time one can not measure temperature or low voltages to any degree of accuracy.

The way I noticed this is that I measured normal 50 Hz 230 V in the Volt range, then switcher over to Freq. mode to measure the frequency. However while doing so you need to cross over the mV range, which will cause a large overvoltage. But as far as I am aware the meter should be able to handle it?! However it seems it does not handle it very well, it causes a temporary (some 30 min) offset in the mV range on the order of several mV!

The same issue would occur if one want to measure Volt and then go to VA and measure VA without disconnecting the probes while crossing the mV range.

I am not sure if this issue has been reported earlier or not. If you need more info/testing let me know.

I am guessing this is hardware related, perhaps some internal capacitance in some IC that gets charged too high and causes incorrect biasing of some stage until it dissipates?
« Last Edit: October 10, 2018, 06:43:03 pm by eV1Te »
 

Offline CDaniel

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Re: EEVblog 121GW Multimeter Issues
« Reply #727 on: October 10, 2018, 07:44:53 pm »
Ok , the meter is able to swallow that overvoltage and survive , but don't expect to be very happy . It's a mistake to switch like that ... and should be a very rare occurrence not something normal as you seem to suggest . Frequency range is for low voltage ( signal ) too , the same as you would use a stand alone frequency meter ...  For AC high voltages frequency you have the secondary display
« Last Edit: October 11, 2018, 05:30:32 am by CDaniel »
 

Offline Seppy

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Re: EEVblog 121GW Multimeter Issues
« Reply #728 on: October 11, 2018, 01:26:49 am »
It's loaded and running now.  I am using the mVDC mode.   I am only looking at the data rate from the MCU to the BLE112.   

I can already tell you that the problem appears to still be there but it may be improved.   Try it on your setup and see if you have similar results.

I cannot reproduce this, I did this on an oscilloscope, I watched the scope for an hour, no jitter.
Is it possible your USART to USB has a buffer or windows is buffering and it is causing the remaining jitter?
 

Offline Seppy

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Re: EEVblog 121GW Multimeter Issues
« Reply #729 on: October 11, 2018, 02:33:52 am »
Sorry, time to head out. 

Consider the following when attempting to replicate my tests:

* The lag can be longer than one second. 
* The lag is aligned on the packet boundary. Or in other words, you need to measure the time between packets and look for missing events.
* When using a separate program to measure the time between packets with the RF interface, it will track the times seen on the serial line going to the BLE112.
* If I run older versions of the firmware prior to 1.10, even though the data rate is doubled, it is stable.

If you scope can measure the time between packets, this is what you want.  A simple thing you could do is just add the timing metric to your application software and trend the data as I have done.

All of the above was considered. I used wires directly soldered to the USART which I then triggered to the start of a packet with some hold off, then measured period between starts of packets.
I might leave it searching for min/max for a day or two.
 

Offline eV1Te

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Re: EEVblog 121GW Multimeter Issues
« Reply #730 on: October 11, 2018, 05:55:18 pm »
Ok , the meter is able to swallow that overvoltage and survive , but don't expect to be very happy . It's a mistake to switch like that ... and should be a very rare occurrence not something normal as you seem to suggest . Frequency range is for low voltage ( signal ) too , the same as you would use a stand alone frequency meter ...  For AC high voltages frequency you have the secondary display

I did not know that the frequency range was only for low volt signals. The manual only says that the input in frequency mode needs to be more than 2.5 V and that it has overvoltage protection up to 600 volt. Does anyone know what voltage range it is designed for?
I have so far used the frequency mode instead of the dual display since it has better resolution.

Even if it is not normal to put 230 VAC on the mV or Ohm/C ranges etc, I know Dave has in the past complained when other meters could not handle such a case. Hence I assumed this meter would not have an issue with it since it is certified by Dave  ;)

By the way I found a different serious bug regarding logging, where all measurements become corrupted/incorrect, will try to replicate it now... Will post it later if can figure out when and why it happens.
 

Offline CDaniel

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Re: EEVblog 121GW Multimeter Issues
« Reply #731 on: October 11, 2018, 09:34:55 pm »
The protection ESD supressor diode is SM6T22CA , so around 22V will start conducting current like 2 zeners in anti-paralel ... and the thermistor in series will start to heat up. For AC sine wave the voltage should be max 15Vrms .
« Last Edit: October 11, 2018, 11:54:03 pm by CDaniel »
 

Offline Seppy

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Re: EEVblog 121GW Multimeter Issues
« Reply #732 on: October 11, 2018, 11:26:46 pm »
It should happen in minutes, assuming the input signal is varying enough to cause the display to change.   One other thing to consider is that the failure rate is low, less than 1%.   It's not something you would want to watch for. 

If you like, I can see if I can capture the events with scope.  I assume your scope was decoding and storing the packets and there was nothing wrong with the data.   If the MCU were corrupting the packet, I would have no way of knowing with my current setup but I certainly could detect a problem like this with the scope.

Do you mean varying enough to cause an autorange, if yes I did not do that, I'll need to.
 

Offline Seppy

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Re: EEVblog 121GW Multimeter Issues
« Reply #733 on: October 12, 2018, 01:37:59 am »
It should happen in minutes, assuming the input signal is varying enough to cause the display to change.   One other thing to consider is that the failure rate is low, less than 1%.   It's not something you would want to watch for. 

If you like, I can see if I can capture the events with scope.  I assume your scope was decoding and storing the packets and there was nothing wrong with the data.   If the MCU were corrupting the packet, I would have no way of knowing with my current setup but I certainly could detect a problem like this with the scope.

Do you mean varying enough to cause an autorange, if yes I did not do that, I'll need to.

I believe I will have an answer for you shortly.   Let me start by apologizing for sending  you, UEI developer's and possibly others, on a wild goose chase on the communications lagging problem I am seeing.    Let me explain where I am at with it.

I changed my test setup to use a scope to monitor the serial communications between the microcontroller and the BLE112.   I set the scope to decode the packets  and then changed my PC software that I use to monitoring the serial bus (using the FTDI controller) so when a lag fault was detected, it sends a trigger signal to the scope.   

138 shows the trigger pulse in red.  Note that the packets before it are not missing.  At first I though maybe a framing error, clock mismatch, etc,  but ...

140 shows the decoding of the first packet prior to the fault.  Everything looks good.   I tried this a few more times and everything seems fine.

So I started looking at my software and realized I had made a mistake in how I architected the packet parsing.   I have not looked into why the pre 1.10 versions worked with my BLE software but suspect that it is linked to the short message.   The parsing is done differently for the UT181A which is why that software does not have a problem.

Of course, I used this same parsing routine for both the 121GW BLE software as well as the serial sniffer.   This is why the two programs tracked the lag as well.   

I have corrected the parser and have been running the serial sniffer using firmware 1.26 and have not seen a single miss.    The BLE software will need to be corrected and then I can repeat all of my testing but I am pretty confident that this is all on my end. 

Again, I am very sorry for not digging into this before bringing it up.   I will let you know in a day or so if I saw any problems. 

|O |O |O |O

No worries I appreciate what you have done. After the firmware change it was a planned test anyway so its good to have more data.
 

Offline chronos42

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Re: EEVblog 121GW Multimeter Issues
« Reply #734 on: October 14, 2018, 07:53:29 am »
Hi,
I also assume that there is something wrong with the 121 GW bluetooth. I have trouble to connect the 121GW with my mobile (Nokia 8 with Android 8.1). The 121GW app cannot find the 121GW. I first must switch off and on the bluetooth function in the 121GW to connect with the meter. No other of my  bluetooth devices behaves like that.
 

Offline chronos42

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Re: EEVblog 121GW Multimeter Issues
« Reply #735 on: October 14, 2018, 05:53:41 pm »
Hi,

no, there is no other bluetooth device active at the same time. Possibly this is a problem with either the Nokia 8 or Android 8.1, I don't know. But the fact that the 121GW is the only (so far) device that has trouble to connect reliable with my phone tells me, that this could point to a problem in the 121GW bluetooth system. Once the 121GW has connected the app shows all data without any problems, but same as your meter it has a very short range until the phone lost the connection. The app can't recover the connection automatically, I have to switch off and on the bluetooth again to restore the connection. For me bluetooth is usable, but not really good.
 

Offline IanB

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Re: EEVblog 121GW Multimeter Issues
« Reply #736 on: October 14, 2018, 06:09:17 pm »
I wonder in your case if you have another device in range that is opening an connection to the meter.  I don't own a cell phone so I can't test  to see if there is a difference with their other applications.   Is anyone else having problems connecting?

I previously had some trouble connecting to Windows 10. I did not reach a conclusion about the causes of that and have not done any investigations since, but I did observe that if the meter was connected to one device it could not connect to a second. In the end I got the connection to Windows 10 reestablished by rebooting the computer. Switching the meter on and off didn't seem to help.
I'm not an EE--what am I doing here?
 

Offline chronos42

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Re: EEVblog 121GW Multimeter Issues
« Reply #737 on: October 14, 2018, 07:24:47 pm »
Hi,

I have used Rev. 1.26. for my tests.

Today I had a strange experience.

Now I am using 1.51 and I tried it again today. Now it connected without any problems several times. Between my tests the 121GW firmware has changed and the mobile also got an update recently, maybe this has solved the problem. :-//

No, don't think so.
Meanwhile I belive you were right, there is very likely a disturbance from other bt devices. Not in my home, but from my neighbours. Because today  the bt receiving range also is much higher than at my last tests. And my direct neightbours are not at home....hmmmm

Now it workes as intended except of one exception. After closing the app and restart it, the app did not see the meter again, I have to switch off and on bluetooth at the meter for reconnecting, like before. But that is not a problem for me.
« Last Edit: October 14, 2018, 08:17:22 pm by chronos42 »
 

Offline IanB

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Re: EEVblog 121GW Multimeter Issues
« Reply #738 on: October 14, 2018, 08:04:35 pm »
I am fortunate that the neighbors are far enough away that they don't cause a problem.   It will be interesting to see when they return if it stops working again.   My CEM meter uses 900MHz with a simple FSK modulation.  I've been amazed at how far that meter will transmit. 

Maybe IanB's problem is similar.

I'm not sure about neighbors with Bluetooth. For example, if I turn on my phone when I am in Fry's I see dozens of BT devices available to connect from all around me. My phone is inundated. If I turn on my phone when I am at home I see no BT devices ever, except the devices I own that I have turned on. Granted there could be long range interference, but the problem I had with Windows 10 seemed more like a Windows 10 problem. My Apple devices have never had any issues connecting.
I'm not an EE--what am I doing here?
 

Offline Antonov225

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Re: EEVblog 121GW Multimeter Issues
« Reply #739 on: November 01, 2018, 09:25:12 am »
Hello EEVBlog!
I feel honored to now be a part of this awesome community. What makes me very sad is that my first post has to be a negative one.

I purchased my 121GW meter on July 26th 2018, during a small batch at official EEVBlog store, after being informed about its availability by the newsletter. Soon I discovered how big mistake I have made.

After receiving the meter and unboxing it, few things immediately stood out. The meter was scratched in many places (especially the knob and in the area around lead sockets) - see attachment. Scratches on two flat sides of the knob clearly came from someone's else fingernails. Part of the knob you grab by your fingers was noticably shinier than other areas. Batteries have also already been put inside the meter - From what I've seen on unboxing videos, these should be included seperately in the pouch.  Conclusion is simple - I recieved a used meter. I thought - "Ok, fine. This is not that bad. I can use this meter nevertheless." And I could - for a month. After that strange things started to happen.

Before making the purchase I did some research online (mainly this forum) and discovered that at some point a common problem with 121GW meters was the knob itself. Apparently there was a recall done at some point regarding the contact issues (knob replacement and addition of a shim). This took place months earlier. Common sense suggested that my meter should have already been free of this issue. This couldn't be farther from the truth.

After a month of very, very light use the meter is basically unusable. The knob wipers stopped making a good contact with the PCB (i think) and the meter reboots constantly while switching modes. Resistance mode cannot be turned on at all. The meter just turns off when I select it. The issue is present for every single knob position.
I made a short video where the issue is clearly visible:



As you can see, this is clearly not a 121GW revision with a fixed knob. I must have received an older, flawed version. This is absolutely unforgivable for a meter this expensive (and every other for that matter). What I find the most frustrating is that the recall was done some time before I bought my meter from the EEVBlog store. At that point I should expect this issue to be already resolved but in the end I recieved a meter with this exact defect still present.

I've sent Dave an email describing these issues on 5th October. He replied a week later and promised to send me a new meter. I was really happy about that. So why am I even writing this post, you may ask? Well, because the new meter has never been shipped and Dave has not replied to any of my emails since then :palm:. I've been trying many times to contact him through at least 3 EEVBlog email adresses and sending him PMs on the forum, asking why the new meter hasn't been shipped. Three weeks have passed and I have not recieved any reply. I have no idea why.

I can only hope that this post will grab Dave's attention and that my meter will get replaced eventually. Do you know if there is any other way to contact Dave or to fix the meter? I just want to be able to use the product i paid for.

Thank you for your help in advance,
A VERY frustrated customer.



 

Offline problemchild

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Re: EEVblog 121GW Multimeter Issues
« Reply #740 on: November 01, 2018, 12:49:05 pm »
I'm sorry to hear this, I really can not comment on the technical problems regarding the meter as I've not played with mine yet as it as only just arrived (yes nearly a month now but you get it!!). Any way I had a similar problem regarding comunications after cleaning up a percieved problem with my address I then asked for confirmation that it was all Ok and the Meter would be sent. After a few weeks I sent another letter to both Daves and then again acouple after and finally yet another a couple of weeks after. At that point I got a reply from Suse the Logistics Lady and my meter arrived all they way from Australia in about 4 days!!

I think that I'm far from been alone in this matter and I also think that Dave isnt been malicious just over worked but we cut him slack since we are not only expecting a quality meter but also hoping to support Dave in a practical manner. That said we dont expect to be ignored for weeks on end, if it wasnt Dave we probably would of made more complaints and probably this would of been picked up by trading standards or by another fancing to make a name by doing to Dave what he's done to others rightly or not!

Dave I hope the Logistics lady is here to stay for a while and keeps it all in order otherwise there will be a queue of replies here I'm sure!
John A
 

Offline bicycleguy

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Re: EEVblog 121GW Multimeter Issues
« Reply #741 on: November 07, 2018, 01:13:08 am »
As noted in Firmware thread, the latest FW at the store is listed as 1.52 shows on the meter as 1.53.

As usual, change log is lagging.  Haven't noticed a difference from 1.51 which disappeared.  What does it all mean  |O
 

Offline alex-sh

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Re: EEVblog 121GW Multimeter Issues
« Reply #742 on: November 12, 2018, 01:45:27 am »
Firmware version 1.51
I cannot check capacitance any more - a little dot is blinking and no values coming up on the screen.
Tried several caps.
 

Offline lowimpedance

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Re: EEVblog 121GW Multimeter Issues
« Reply #743 on: November 12, 2018, 05:08:20 am »
Have you tried 1.52 (1.53) ?.
The odd multimeter or 2 or 3 or 4...or........can't remember !.
 

Offline link87

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Re: EEVblog 121GW Multimeter Issues
« Reply #744 on: November 13, 2018, 06:23:46 pm »
Quote
As usual, change log is lagging

Is the ChangeLog available somewhere other than the manual? Seems like it ought to be included in the firmware ZIP or at least as a link beside the download link for it.
 
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Offline Candid

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Re: EEVblog 121GW Multimeter Issues
« Reply #745 on: November 13, 2018, 06:32:38 pm »
This would be way to easy  ::)
 

Offline alex-sh

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Re: EEVblog 121GW Multimeter Issues
« Reply #746 on: November 18, 2018, 01:13:42 pm »
Quote
As usual, change log is lagging

Is the ChangeLog available somewhere other than the manual? Seems like it ought to be included in the firmware ZIP or at least as a link beside the download link for it.

Thanks for heads up. Yes, in 1.53 the bug with capacitance has been corrected. However, the manual is not updated.
Anyone knows what has been done in 1,53?
 

Offline rattnallen

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Re: EEVblog 121GW Multimeter Issues
« Reply #747 on: November 21, 2018, 02:18:14 pm »
Firmware version 1.57 at https://www.eevblog.com/product/121gw/
The manual is still not updated ...
 

Offline CDaniel

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Re: EEVblog 121GW Multimeter Issues
« Reply #748 on: November 22, 2018, 10:16:00 pm »
It is very good that now we have improved capacitance mode .

But I can't understand how a team of profesional coders make a software and not check the basics - now in manual mode is not showing "overrange" , the display just freeze or show 0.000 .

Autoranging an 100uF capacitor is going into 10.00mF range so you see only 2 digits , 97uF for exemple .
10nF , 100nF , 1uF , 10uF seems to be fine ...

Other issues not corrected yet ...
In resistance mode , the autorange hysteresis is way too big , switch in upper range at 55000 counts but down at 40000 counts . So , as the resistance ranges switch from high to low resistance , a 470ohm resistor is showing 0.4700 in 5K range not at full resolution in 500ohm range as should be .

In voltage mode hysteresis is too big also .
This cause problems when measuring something in between , loss of resolution when measuring variable or adjustable voltages .
For a 50.000 counts multimeter I think it is normal to switch at 55.000 counts up and probably at 51.000 down , to have 50.000 counts all the time . And 5V is the most used voltage in electronics ... this value should never be in hysteresis


Edit
Interesting , when measuring capacitors in manual range is showing overrange if the capacitor is not too big , so in 10nF range is showing overrange for 100nF but just freeze for 10uF ...
« Last Edit: November 22, 2018, 10:46:12 pm by CDaniel »
 

Offline 1anX

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Re: EEVblog 121GW Multimeter Issues
« Reply #749 on: November 23, 2018, 02:26:51 am »
Edit
Interesting , when measuring capacitors in manual range is showing overrange if the capacitor is not too big , so in 10nF range is showing overrange for 100nF but just freeze for 10uF ...

Confirmed

Sheesh, two EEVBlog engineers and an instrument manufacturer like UEI, you would think they would have a test procedure worked out for firmware revisions by now!

If Dave was reviewing this meter and its updates on EEVBlog it would rate the dreaded FAIL conclusion.

If Dave is looking to bring out a version 2 of this meter, the thing needing change the most would be their testing procedures because at the moment its not professional.

My verdict is that the 121GW has potential, but is hampered by the driving force behind it, namely Dave being more interested in releasing regular blogs than fixing the meters problems.

I own one of these meters and am looking forward to the good faith shown by supporting the kickstarter being returned by proper quality checks and testing. Its so close, but still so far from being a great meter!
 
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