Brymen BM789

[joeqsmith]

For those interested in the exact details here:

uses hi-speed AD conversion data to do Auto-ranging mechanism. After switching from 600Ω Range to 6kΩ Range, firmware used the first hi-speed AD conversion data to deduct "600Ω Range Offset" to check if further Range-Switching was in need. In case "600Ω Range" and "6kΩ Range" have significant offset difference, the unit may not be able to converge the measurements at around 640Ω ~ 660Ω region in auto-ranging operation mode. Thus not every unit will have this bug. Only the unit with extreme offset difference case has this bug.

Our engineer has modified the firmware to fix this bug. After switching from 600Ω Range to 6kΩ Range, the update firmware version uses the first hi-speed AD conversion data to deduct "6kΩ Range Offset" instead to check if further Range-Switching is in need.

You've been reading my emails again...

[joeqsmith]

Demo of firmware version 78911 which addresses the auto ranging problem mentioned earlier. 
 

[EEVblog]

Demo of firmware version 78911 which addresses the auto ranging problem mentioned earlier. 

Did they give you the chip programmer?

[AVGresponding]

Demo of firmware version 78911 which addresses the auto ranging problem mentioned earlier. 

Did they give you the chip programmer?

Surely they will have just sent an updated chip or meter?

[EEVblog]

Did they give you the chip programmer?

Surely they will have just sent an updated chip or meter?

He said it's the same meter, so either a new chip or he's got a programmer now.

[Chalcogenide]

I was looking at the Youtube video's comments and in a reply OP states "I changed the IC on the one I demonstrated." so it's fair to say that Brymen did not provide him a programmer but just a pre-programmed IC to replace in his meter.

[floobydust]

I thought Joe was blowing up the DMM IC U1, not the MCU U16?
Doesn't matter really, the firmware is cast in stone unless you want to ship it across the ocean. Brymen could have trusted agents in North America do F/W upgrades, repairs... or maybe not due to their obligations as an OEM which prevents them from selling here.
Could look at the Andes programmer but you'd still need the binary.

[c0d3z3r0]

@joeqsmith @EEVblog is 78911 the most recent firmware?

I got a new BM789 from @Welectron with FW 78908  They have no newer fw in stock and can't update the firmware. So, I'm sitting here with a shiny new DMM with buggy firmware....
They said they'll contact Brymen and I might send it to them (Brymen) for update. Not really what I want to do with a new device, tbh.
I hope they'll find a customer-friendly solution.

EDIT: Just to clarify, I don't want to blame Welectron for that Problem, I'm sure they'll give their best to solve this :-)

[NoMoreMagicSmoke]

Do you actually have any issues with your meter? I have an identical meter to yours, and mine does not demonstrate the resistance glitch.

[EEVblog]

@joeqsmith @EEVblog is 78911 the most recent firmware?

I got a new BM789 from @Welectron with FW 78908  They have no newer fw in stock and can't update the firmware. So, I'm sitting here with a shiny new DMM with buggy firmware....
They said they'll contact Brymen and *I* might send it to them (Brymen) for update. Not really what I want to do with a new device, tbh.
I hope they'll find a customer-friendly solution.

It honestly isn't a big deal. It's almost certain that you'll never encounter the bug, and if you do then it's obvious and you can just switch to manual range.
This is how every Brymen meter and most other brands and model have worked since time immemorial.

[EEVblog]

Do you actually have any issues with your meter? I have an identical meter to yours, and mine does not demonstrate the resistance glitch.

Yes, only some meters exhibit the problem. Brymens response as to why this is the case has been posted.

[c0d3z3r0]

Well, my BM789 simply shows 0 Ohms then. I wouldn't call that *obvious*. Also, when pressing "RANGE" it sometimes simply turns off completely...

[NoMoreMagicSmoke]

Well, my BM789 simply shows 0 Ohms then. I wouldn't call that *obvious*. Also, when pressing "RANGE" it sometimes simply turns off completely...

That's something completely different than the bug that was recently fixed. Does it ever change from 0 ohms?

[Monkeh]

Well, my BM789 simply shows 0 Ohms then. I wouldn't call that *obvious*. Also, when pressing "RANGE" it sometimes simply turns off completely...

Err, that is not the described fault, and shutting off when changing range is not normal either.

[c0d3z3r0]

Well, my BM789 simply shows 0 Ohms then. I wouldn't call that *obvious*. Also, when pressing "RANGE" it sometimes simply turns off completely...

That's something completely different than the bug that was recently fixed. Does it ever change from 0 ohms?

I don't think so. For me this happens around 660 Ohms. Yes, it changes, when either changing the resistor value or when range switching works - each 3-4th doesn't...

[c0d3z3r0]

Well, my BM789 simply shows 0 Ohms then. I wouldn't call that *obvious*. Also, when pressing "RANGE" it sometimes simply turns off completely...

Err, that is not the described fault, and shutting off when changing range is not normal either.

A different symptom, but probably the same bug

[NoMoreMagicSmoke]

Well, my BM789 simply shows 0 Ohms then. I wouldn't call that *obvious*. Also, when pressing "RANGE" it sometimes simply turns off completely...

That's something completely different than the bug that was recently fixed. Does it ever change from 0 ohms?

I don't think so. For me this happens around 660 Ohms. Yes, it changes, when either changing the resistor value or when range switching works - each 3-4th doesn't...

This is very interesting. Any chance of posting a video?

[joeqsmith]

I thought Joe was blowing up the DMM IC U1, not the MCU U16?
Doesn't matter really, the firmware is cast in stone unless you want to ship it across the ocean. Brymen could have trusted agents in North America do F/W upgrades, repairs... or maybe not due to their obligations as an OEM which prevents them from selling here.
Could look at the Andes programmer but you'd still need the binary.

As for blowing up ICs with both the Brymen BM786 & BM789, I suspect that thin Canada air causes hallucinations.   I pushed the prototype BM786 to failure (12kV peak) in the following video and damaged Q4.  The set was replaced and I continued my testing of the meter.  Because the two meters share the same front end, I only ran the BM789 on the 6kV generator.   Personally I consider meters that have protection circuits that limit the amount of damage to allow repairs a big plus.   Consider that the $600+ Keysight meter I just looked was damaged beyond repair at 5kV.     

Damaging the Brymen BM786 prototype at 12kV and then repairing it by replacing two transistors:


Damaging the Keysight U1282A at 5kV and taking out several IC, some custom. 

[joeqsmith]

Well, my BM789 simply shows 0 Ohms then. I wouldn't call that *obvious*. Also, when pressing "RANGE" it sometimes simply turns off completely...

Err, that is not the described fault, and shutting off when changing range is not normal either.

A different symptom, but probably the same bug

Agree with Smokey the Bear, make a short video showing the behavior.   If you have found a new problem and I am able to replicate it, there is a good chance we could work with Brymen to address it.   

@joeqsmith @EEVblog is 78911 the most recent firmware?

As of three weeks ago when I posted that last video it was.  I'm not a distributor and am in no way affiliated with Brymen.  The only way for you to know for sure would be for you to ask them.   

[c0d3z3r0]

Well, my BM789 simply shows 0 Ohms then. I wouldn't call that *obvious*. Also, when pressing "RANGE" it sometimes simply turns off completely...

Err, that is not the described fault, and shutting off when changing range is not normal either.

A different symptom, but probably the same bug

Agree with Smokey the Bear, make a short video showing the behavior.   If you have found a new problem and I am able to replicate it, there is a good chance we could work with Brymen to address it.   

Sure, I made a video now. There are two things you can see 1) weird jumping of the measure value after a second or so and 2) now random resetting of the DMM when switching through ranges, instead of turning off o.O
https://www.veed.io/view/261c54f7-b4a1-4e5e-89cc-e05c4cb08251

Fun fact... I am unable to reproduce the 0 Ohms readings anymore. I should have filmed that earlier . However, the resetting behaviour got worse as you can see. This *only* happens around 66x Ohms (666...  ).
1 happens regardless of the resistor value, but seems unusual to me and I never saw such thing with other DMMs, what do you think? Here's another video of that:
https://www.veed.io/view/e9a4ccda-ac7c-4aba-a357-9880bcae5435

@joeqsmith @EEVblog is 78911 the most recent firmware?

As of three weeks ago when I posted that last video it was.  I'm not a distributor and am in no way affiliated with Brymen.  The only way for you to know for sure would be for you to ask them.

Thank you. I already sent them a message. I guess that will take some days.

[floobydust]

Pressing the Manual range button might just be aggravating a bad connection inside. See if it's the rotary switch, try applying some pressure, a gentle squeeze to the switch instead.

[floobydust]

I thought Joe was blowing up the DMM IC U1, not the MCU U16?
Doesn't matter really, the firmware is cast in stone unless you want to ship it across the ocean. Brymen could have trusted agents in North America do F/W upgrades, repairs... or maybe not due to their obligations as an OEM which prevents them from selling here.
Could look at the Andes programmer but you'd still need the binary.

As for blowing up ICs with both the Brymen BM786 & BM789, I suspect that thin Canada air causes hallucinations.   I pushed the prototype BM786 to failure (12kV peak) in the following video and damaged Q4.  The set was replaced and I continued my testing of the meter.  Because the two meters share the same front end, I only ran the BM789 on the 6kV generator.   Personally I consider meters that have protection circuits that limit the amount of damage to allow repairs a big plus.   Consider that the $600+ Keysight meter I just looked was damaged beyond repair at 5kV. [...]

In your Brymen BM786 DMM Part 3 video you mentioned getting a new MCU and putting that in, I assumed it got damaged at 12kV.

Did they give you the chip programmer?

Surely they will have just sent an updated chip or meter?

He said it's the same meter, so either a new chip or he's got a programmer now.

He appears to be replacing the MCU, but the air is thick 

[joeqsmith]

In your Brymen BM786 DMM Part 3 video you mentioned getting a new MCU and putting that in, I assumed it got damaged at 12kV.

Maybe just watch the first minute of Part 3 where I explain the reason for the change.   

[joeqsmith]

Sure, I made a video now. There are two things you can see 1) weird jumping of the measure value after a second or so and 2) now random resetting of the DMM when switching through ranges, instead of turning off o.O
https://www.veed.io/view/261c54f7-b4a1-4e5e-89cc-e05c4cb08251

Fun fact... I am unable to reproduce the 0 Ohms readings anymore. I should have filmed that earlier . However, the resetting behaviour got worse as you can see. This *only* happens around 66x Ohms (666...  ).
1 happens regardless of the resistor value, but seems unusual to me and I never saw such thing with other DMMs, what do you think? Here's another video of that:

I only saw the one value in the video.  Odd it wouldn't reset like this with other values as it seems like a mechanical problem.    Sorry but I wasn't able to replicate it with the meters I have.   

[Monkeh]

Well, my BM789 simply shows 0 Ohms then. I wouldn't call that *obvious*. Also, when pressing "RANGE" it sometimes simply turns off completely...

Err, that is not the described fault, and shutting off when changing range is not normal either.

A different symptom, but probably the same bug

Agree with Smokey the Bear, make a short video showing the behavior.   If you have found a new problem and I am able to replicate it, there is a good chance we could work with Brymen to address it.   

Sure, I made a video now. There are two things you can see 1) weird jumping of the measure value after a second or so and 2) now random resetting of the DMM when switching through ranges, instead of turning off o.O
https://www.veed.io/view/261c54f7-b4a1-4e5e-89cc-e05c4cb08251

With that behaviour I would simply go to Welectron and have it replaced.