Brymen BM789

[EEVblog]

Try measuring the variable resistor. In the range of 650-660 ohms in automatic mode, he goes crazy.

I wonder if this is an issue with just some meters? I just tried with a potentiometer and s sweep from 600-700 6.0k - 7.0k could not cause the meter to freak out. My meter is 08 and it ranges up at 66000 counts and down at 61000 counts.

I did only have a 1 turn pot available though so it's possible it's a very narrow range and I didn't have the resolution on the potentiometer to hit the sweet spot.

No issue at all on a new BM786 with 78608 firmware, or 78607 using my decade resistance box. It's just rock solid at 0.65x display.

[joeqsmith]

Try measuring the variable resistor. In the range of 650-660 ohms in automatic mode, he goes crazy.

I wonder if this is an issue with just some meters? I just tried with a potentiometer and s sweep from 600-700 6.0k - 7.0k could not cause the meter to freak out. My meter is 08 and it ranges up at 66000 counts and down at 61000 counts.

I did only have a 1 turn pot available though so it's possible it's a very narrow range and I didn't have the resolution on the potentiometer to hit the sweet spot.

No issue at all on a new BM786 with 78608 firmware, or 78607 using my decade resistance box. It's just rock solid at 0.65x display.

That's odd.   I had to hunt for it but was able to find a spot were the 789 will hunt indefinitely as suggested by the OP.   

[joeqsmith]

I should add that the 789 shown was the last meter I tested which had been setup at the factory.  It is not one of the meters I had swapped parts on.

Also, maybe a bit more to the story.  Looking at one of the 786 meters, w/ 78605 which had modified with the latest parts of that time, does not exhibit this problem. 

As I mentioned, I had forwarded this information to Brymen.   

[GAVER]

I confirm the problem.78909

[EEVblog]

I should add that the 789 shown was the last meter I tested which had been setup at the factory.  It is not one of the meters I had swapped parts on.
Also, maybe a bit more to the story.  Looking at one of the 786 meters, w/ 78605 which had modified with the latest parts of that time, does not exhibit this problem. 
As I mentioned, I had forwarded this information to Brymen.

The 786 and 789 firmware bases are different. Possible it exists in one and not the other.
I've gone up by 1 ohm increments from 600ohm to 680ohm and there is no problem.

[PushUp]

Unfortunately, the "new" Benning MM 7-2 with "FW 72001" has the same problem/bug:







I found the spot with my "Vishay Precision Potentiometer" immediately @ 661.x Ohm,....







....however, the MM 7-2 does not autorange for ever, but simply shows OL after autoranging (it is not as fast as the other DMMs).
When I pull the test leads out of the MM 7-2 and put them back in, it shows an interim value before going back straight to OL.







After that I only had to swap the test leads into the Fluke 289:






..., the Keysight U1273A...


foto fun kostenlos



...and the PM XTRA,...







...which have not any issue, showing the "right" resistance instantly depending on its precision.




...and back it goes...! 



Cheers! 

[joeqsmith]

I should add that the 789 shown was the last meter I tested which had been setup at the factory.  It is not one of the meters I had swapped parts on.
Also, maybe a bit more to the story.  Looking at one of the 786 meters, w/ 78605 which had modified with the latest parts of that time, does not exhibit this problem. 
As I mentioned, I had forwarded this information to Brymen.

The 786 and 789 firmware bases are different. Possible it exists in one and not the other.
I've gone up by 1 ohm increments from 600ohm to 680ohm and there is no problem.

Based on the posts, it seems so. 

I have confirmation that Brymen is now working on it.   Guessing the OP did not contact them as it did not seem like they were made aware of the problem until now.      I'll post an update when I have it.   

[TCbystander]

....however, the MM 7-2 does not autorange for ever, but simply shows OL after autoranging (it is not as fast as the other DMMs).
When I pull the test leads out of the MM 7-2 and put them back in, it shows an interim value before going back straight to OL.

Seems like you were using the continuity function, not the resistance function instead

[coromonadalix]

hmmmm seems like it  since you have the continuity beep  logo on the screeen ??

[PushUp]

I am quite sure, that I was in Ohms mode, when I did my decisive measurement, as I saw different values, when I searched for the 660 Ohms region and have just forgotten to pay attention to the settings, when doing the photosession behind the other DMMs, after playing around with the buttons of the MM 7-2, which also keeps the last settings...

As I have already sent the Benning back home, I cannot repeat my measurement. However, as I don't want to ruin Bennings sellings, I hope that I was mistaken and quote the assumption of innocence for Benning with its MM 7-2 and their FW 72001, that they have paid attention to the mentioned bug, as they should know, which older Brymen-FW they use as their own first FW-Version "72001"...

Next time I will make a video for myself, having a better proof of concept, as I am also annoyed about my lousy documentation, but as I will not buy a Brymen/Benning again, maybe someone else is willing to repeat the test, because what I can definitely say is, that I am totally happy with my aleady bought handheld DMMs and don't see any reason to buy another one... 

Sorry & Cheers! 

[Antrus]

And what will be the correction of this error on the part of the manufacturer? Previous buyers will stay with her. Maybe the controller can be read and flashed with a programmer from Stm32?
Why is there no BRYMEN representative on this forum?

[GAVER]

Дрючить техподдержку Brymen
, я уже дрючу!
Druchit  tech support Brymen
I'm already druchu!

[EEVblog]

And what will be the correction of this error on the part of the manufacturer? Previous buyers will stay with her. Maybe the controller can be read and flashed with a programmer from Stm32?
Why is there no BRYMEN representative on this forum?

Every single Brymen meter ever made before this 78x series (and many other brands including the biggies like Fluke) do not allow firmware updating, so you are stuck with the version you bought.
There is no manufacturer or dealer re-programming service offered.

[joeqsmith]

....however, the MM 7-2 does not autorange for ever, but simply shows OL after autoranging (it is not as fast as the other DMMs).
When I pull the test leads out of the MM 7-2 and put them back in, it shows an interim value before going back straight to OL.

As I have already sent the Benning back home, I cannot repeat my measurement.

Someone commented how they were using the LoZ to look at a battery, then measuring the battery with the standard voltage mode and would see the voltage slowly drift upward.  They were blaming the DMM and also returning it.   I think that's the jist anyway.  I am waiting for them to make a short video showing it. 

[AVGresponding]

....however, the MM 7-2 does not autorange for ever, but simply shows OL after autoranging (it is not as fast as the other DMMs).
When I pull the test leads out of the MM 7-2 and put them back in, it shows an interim value before going back straight to OL.

As I have already sent the Benning back home, I cannot repeat my measurement.

Someone commented how they were using the LoZ to look at a battery, then measuring the battery with the standard voltage mode and would see the voltage slowly drift upward.  They were blaming the DMM and also returning it.   I think that's the jist anyway.  I am waiting for them to make a short video showing it.

Really? I can understand the buyer being too dumb to understand what they are doing (if it's as you describe), but surely the seller should have some basic level of knowledge of the products they are supplying..? I would refuse a return on this basis anyway.

[joeqsmith]

Really? I can understand the buyer being too dumb to understand what they are doing (if it's as you describe), but surely the seller should have some basic level of knowledge of the products they are supplying..? I would refuse a return on this basis anyway.

Thank you for asking.  We are talking the WWW and there can certainly be differences in language, culture, education and our friendly trolls from time to time.  Lots of dynamics and you may interpret the discussion differently.   I welcome the input. 

[floobydust]

[...] Every single Brymen meter ever made before this 78x series (and many other brands including the biggies like Fluke) do not allow firmware updating, so you are stuck with the version you bought.
There is no manufacturer or dealer re-programming service offered.

I think Brymen needs to acknowledge the need to update the firmware in their multimeters. With feature sets now this complicated, updates are to be expected, the days of OTP are thankfully gone. There's not a lot of secret sauce in the firmware and supposedly they have custom silicon as well.
If Brymen is scared then let authorized dealers or a repair depot do it. Oh wait there's none in North America.

Fluke had top quality firmware, it was tested thoroughly, there is no comparison in that regard.

[AVGresponding]

Really? I can understand the buyer being too dumb to understand what they are doing (if it's as you describe), but surely the seller should have some basic level of knowledge of the products they are supplying..? I would refuse a return on this basis anyway.

Thank you for asking.  We are talking the WWW and there can certainly be differences in language, culture, education and our friendly trolls from time to time.  Lots of dynamics and you may interpret the discussion differently.   I welcome the input.

I see. Looks like you are doing your best to explain to someone with zero knowledge why battery voltage drops when loaded, and then recovers once the load is removed... I wish you luck!

[AVGresponding]

[...] Every single Brymen meter ever made before this 78x series (and many other brands including the biggies like Fluke) do not allow firmware updating, so you are stuck with the version you bought.
There is no manufacturer or dealer re-programming service offered.

I think Brymen needs to acknowledge the need to update the firmware in their multimeters. With feature sets now this complicated, updates are to be expected, the days of OTP are thankfully gone. There's not a lot of secret sauce in the firmware and supposedly they have custom silicon as well.
If Brymen is scared then let authorized dealers or a repair depot do it. Oh wait there's none in North America.

Fluke had top quality firmware, it was tested thoroughly, there is no comparison in that regard.

Maybe just wishful thinking, but I'd prefer a meter that works straight away, and not one that might work 7 firmware patches and 2 years down the line. Much of the time the issues Joe and others uncover are really not edge cases and should really be picked up at the R&D stage. This is not an issue exclusive to Brymen, either. The Fluke 87V has a firmware fault, that afaik exists even today, and has been explored on this forum. It's not a serious one, but it exists nevertheless.

I'd also worry that a used meter purchased off ebay or wherever, might have non-manufacturer firmware that may even cause safety issues, and I expect the manufacturers have similar concerns, as well as wanting to protect their IP of course.

[NoMoreMagicSmoke]

Fluke had top quality firmware, it was tested thoroughly, there is no comparison in that regard.

I am not sure this is really a fair statement. Fluke is not immune to rare firmware bugs and has had some themselves (87V GSM bug???). There have been a number of reviewers and this meter has been out for a couple of years now before this issue was found. I have a BM789 with firmware version 08 and I attempted to reproduce this and I could not with my meter. This means that either this issue does not affect all BM789 meters, or it is an extremely narrow scoped issue.

I guarantee that anything with software has edge case bugs that if you search for long enough can be uncovered. The fact that someone can find an obscure bug does not mean that the product is inferior. The company's response though does separate the good from the bad.

[joeqsmith]

....
The company's response though does separate the good from the bad.
...

[floobydust]

Fluke had top quality firmware, it was tested thoroughly, there is no comparison in that regard.

I am not sure this is really a fair statement. Fluke is not immune to rare firmware bugs and has had some themselves (87V GSM bug???). There have been a number of reviewers and this meter has been out for a couple of years now before this issue was found. I have a BM789 with firmware version 08 and I attempted to reproduce this and I could not with my meter. This means that either this issue does not affect all BM789 meters, or it is an extremely narrow scoped issue.

I guarantee that anything with software has edge case bugs that if you search for long enough can be uncovered. The fact that someone can find an obscure bug does not mean that the product is inferior. The company's response though does separate the good from the bad.

Fluke I thought it was a hardware bug a very long time ago, sensitivity to RF and the recall and ferrite bead added.

Basic F/W testing includes the boundary conditions. I'm not sure why a range change is even necessary here unless they have a quality problem with the Ohms current source variations and the DMM IC. You'd have to measure the Ohms test current when it's hunting and see it's likely moving around.
I'd be upset to spend ~$80 to ship to Taiwan for a F/W update. If a bug is found that includes a safety issue, Brymen would have to eat it.

[EEVblog]

If Brymen is scared then let authorized dealers or a repair depot do it. Oh wait there's none in North America.

And who's going to pay for all the shipping and time?

Fluke had top quality firmware, it was tested thoroughly, there is no comparison in that regard.

https://www.eevblog.com/forum/testgear/fluke-87v-87-5-87-v-gsm-interference-fluke-says-firmware-flash-fixes-it/

I used to have a 70 series Fluke at work that had an autoranging problem when meanruing mains transformer primaries, it just kept autoranging, displaying nothing.

[EEVblog]

I'd also worry that a used meter purchased off ebay or wherever, might have non-manufacturer firmware that may even cause safety issues, and I expect the manufacturers have similar concerns, as well as wanting to protect their IP of course.[/color][/size][/b]

Yes, these concerns have been cited to me by Brymen, Kane, Fluke, and Keysight.

[EEVblog]

I guarantee that anything with software has edge case bugs that if you search for long enough can be uncovered. The fact that someone can find an obscure bug does not mean that the product is inferior. The company's response though does separate the good from the bad.

And what should that response be?
Fluke for example very quietly fixed it in production units about 12 months later and made no mention of it at all to new or existing customers. A customer would have no idea what version they were buying.