Brymen BM789

[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...

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.

I agree with he others that said get a replacement. Looks like you light have gotten a dud

[c0d3z3r0]

Greetings to all. I have a question about measuring resistance with this multimeter. At first it shows a slightly lower value, after a second the final one. Is it so for everyone? Firmware 78908.In reviews, he showed the value immediately.

Couldn't reproduce the issue on my 78905 at any of the range transitions.

~655.xx does show as 0.622xx for a full second before settling on 0.655xx.  Also noticed the same behavior if you switch to mV and back at that approximate value.

So, I am no the only one...

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.

As I said, this *only* happens around 660 Ohms.

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.

Check the second video. There's two values, as described by J-R.

How can a mechanical problem be tied to a specific value? ;-)

Anyway, I alread had contacted Welectron. Let's see what they come up with next week.

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

[joeqsmith]

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.

Check the second video. There's two values, as described by J-R.

How can a mechanical problem be tied to a specific value? ;-)

Both videos show 664 ohms.  There was nothing shown that suggests the meter would behave differently with another value.   If it is tied to a specific value as you suggest, I would suggested leaving the leads open or shorted to show that. 

So yes, it appears like a mechanical problem to me. 

[c0d3z3r0]

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.

Check the second video. There's two values, as described by J-R.

How can a mechanical problem be tied to a specific value? ;-)

Both videos show 664 ohms.  There was nothing shown that suggests the meter would behave differently with another value.   If it is tied to a specific value as you suggest, I would suggested leaving the leads open or shorted to show that. 

So yes, it appears like a mechanical problem to me.

The second video *clearly* shows 0.6401, then 0.6639 - exactly as both J-R and Antrus already described.

Ahh, I see, you don't believe anything you haven't seen on a video. Got it.....
Then watch this - no mechanical problem! https://www.veed.io/view/1b8810ab-a6ca-44b4-90ac-27d78e7bf110

(Now you tell me, that you don't believe it's one and the same DMM? *scnr*)

[joeqsmith]

Notice you removed the leads, adding one more variable to the mix.  Also the technique changed along with where you were pressing.   True, I don't know what firmware was installed on this meter.  Was it indeed different?   

[floobydust]

If it's not a mechanical problem, it might be the old F/W has a problem with the act of selecting manual range (mode) when the auto-ranging it hasn't yet settled or it converged at the seam, and then it appears to reboot?

[joeqsmith]

If that's true, he could have tried a 100 and 1k or so to move it away from that switch point but still give roughly the same settling time.     

[c0d3z3r0]

If that's true, he could have tried a 100 and 1k or so to move it away from that switch point but still give roughly the same settling time.   

I already said that this doesn't happen for other values. I don't have to prove everything with a video, though.

[c0d3z3r0]

@joeqsmith Regarding that second issue (jumping value), your BM789 with 78908 shows the same behaviour. Just look at your own video
https://youtu.be/siPjGNL6U0E?t=92
The dmm first shows 0.6358k, then after a second switches to 0.6998k.
This is gone with 78911 later in that video.

[armandine2]

I don't have to prove everything with a video, though.

The video is a representation of what has happened, presumably - as you yourself have just demonstrated with your analysis of Joe's video.

or am I missing something

[joeqsmith]

Sorry,  I don't see the problem. 

***
Are you expect meters will always settle on one read?   

[AlexTee]

Just noticed, Welectron is now offering paid firmware update service for BM78x series: https://www.welectron.com/Brymen-BM780-Firmware-Update_1

Has anybody tried this out so far? Specifically, interested in whether the DMM persists its factory calibration after their update procedure?

[EEVblog]

Has anybody tried this out so far? Specifically, interested in whether the DMM persists its factory calibration after their update procedure?

Yes it keeps the factory calibration.
They would be using the exact same tool and process that I have.

[giosif]

Hi,

Just got my BM789 with a plan to make it my go-to DMM, but I've noticed a few "oddities" (in no particular order):
1. When in Diode mode, sometimes, if I short the probes, I get a short beep, followed by a pause of 1-2 seconds, and only then I get the continuous beep and flashing backlight.
   The other times, the meter starts beeping continuously and flashing the backlight right away.
   In fact, you can kind of see this behaviour in my video below, when playing with the rotary switch.
   Not a big problem, but can still a bit annoying from the perspective of inconsistent behaviour, when you are troubleshooting something.

2. Low battery indicator - as per the video, the threshold for this is different for the different functions.
   For example, I did some measurements and, when in ACV measurement mode, the threshold for displaying low battery is approx. 3.76V.
   At the same time, the threshold for displaying low battery when in DCV mode is 3.58V.
   Is this intended, I wonder (i.e. Brymen feel confident the meter will display accurate DCV readings even with lower battery levels?)?

3. Rotary selection switch - in my brief time spent with the meter (got it only a few days back), it already happened that I wanted to switch to Diode mode and, without connecting the probes to anything, the meter starting beeping as when measuring a short.
   When I looked a bit more carefully, I noticed the rotary switch had ended up between functions (namely, between Capacitor/Diode and Temp).
   Once I set the switch to the correct position, everything went back to normal.
   In the video, I tried to replicate this issue but I had to explicitly try to get it into an intermediate position and try a few times in order to succeed.
   Subsequent attempts seemed to be easier to replicate it, though.
   In any case, given I encountered this under normal use once already, and this in less than a week since I got it, I am concerned it will become a recurring problem.
   Has anyone else encountered this and, if so, how often does it happen to you?

In short, I want to love this meter, but the above, and especially point 3 above, rather puts me off.
Am I being too picky here?

Thanks!

Link to the video - https://youtu.be/kEJgoO0yBYo

[giosif]

[...]
2. Low battery indicator - as per the video, the threshold for this is different for the different functions.
   For example, I did some measurements and, when in ACV measurement mode, the threshold for displaying low battery is approx. 3.76V.
   At the same time, the threshold for displaying low battery when in DCV mode is 3.58V.
   Is this intended, I wonder (i.e. Brymen feel confident the meter will display accurate DCV readings even with lower battery levels?)?
[...]

Adding to the above, just noticed this mentioned in the manual for the BM789:
"Low Battery: Below approx. 3.7V"
So, that means there is an issue with the meter not displaying the low battery indicator in DCV (Ohms and others as well) until battery level reaches about 3.58V.
Maybe this was addressed in fw version 78911?
Anyone willing to check?

[J-R]

I have a 78905.

1) I can reproduce the diode issue if I turn the DMM on, go straight to that mode and short the leads right away.

2) Low battery behavior is a complex issue IMHO, especially when you consider the discharge curves of various chemistries and how they act under load.  Then throw the backlight into the mix and it's a bit of a minefield for detection.  But on the flip side, in normal use the backlight will probably cause the low battery indicator to come on first, so that may be the most consistent indicator.

3) Yes, I have had the issue with the Brymen selector switch ending up between positions.  Some years ago my BM235 did that very badly when I turned it off and somehow ended up between Off and AutoV.  I put it away for a while and some weeks later the plastic had malformed and the switch literally flopped in the breeze.  I reversed the process over another few weeks and that fixed it.

Since then, I have been taking apart my Brymen DMMs and adding a small amount of lubricant to specific areas of the selector switch mechanism. I also add a tiny amount of precision lube to the contacts on the PCB.  Between the two, the selector feels a lot nicer to me, but maybe that is personal preference.  Due to the short warranty and overseas shipping costs, I consider all my Brymen DMMs to be disposable.


If you just purchased your BM789, it might already have firmware 11.  What version is yours?  (Turn on while holding ▲.)

[sonpul]

1. A 0.5 second interruption occurs in BeepLit™ Diode Alert operation. I work with the device daily and intensively. If you had not paid attention to this moment, I would not have noticed it.

2. I use 3xAAA Panasonic Eneloop Pro batteries, BM789 lasts a very long time with them. The battery icon is present when measuring V~ and mV dBm. The measurements are accurate, but I'm just heeding this nutritional warning. Maybe in these truerms modes, the nominal voltage is desirable for the converter.

3. I can create a beep by switching between diode continuity and temperature. But in thousands of measurements, I have not set the switch in this position.

BM789 is so good and convenient that you stop paying attention to these "shortcomings"

[mwb1100]

(I don't have a BM789 but a BM786)

2. Low battery indicator - as per the video, the threshold for this is different for the different functions.
   For example, I did some measurements and, when in ACV measurement mode, the threshold for displaying low battery is approx. 3.76V.
   At the same time, the threshold for displaying low battery when in DCV mode is 3.58V.
   Is this intended, I wonder (i.e. Brymen feel confident the meter will display accurate DCV readings even with lower battery levels?)?

It would not occur to me that a low battery indicator showing in some modes but not others when the battery is at the edge of a low voltage condition would be considered a problem unless readings were wrong.

3. Rotary selection switch - in my brief time spent with the meter (got it only a few days back), it already happened that I wanted to switch to Diode mode and, without connecting the probes to anything, the meter starting beeping as when measuring a short.
   When I looked a bit more carefully, I noticed the rotary switch had ended up between functions (namely, between Capacitor/Diode and Temp).

I can't recall ever landing between settings.  But if you believe this might happen again more than once in a a blue moon (or once in a lifetime), then you might want to consider an exchange or different meter.  I'd guess that landing between positions accidentally was a fluke though.  But there has been selector oddness discussed before (things like pressing on the selector would cause the meter to misbehave, and if I remember right, Dave did a video diagnosing a BM786 problem that turned out to be a defect on the the selector's PCB contact area).  I believe those problems were one-off defects rather than problems with the BM78x design.

[Neutrion]

1.
FW version 08 here. The beeplit has this short pre-beep also but not with a one second brake, but rather maybe a tenth of a second. And yes sometimes it doesn't prebeep, but I never noticed this when working with it. You want to keep the probes connected to have a good contact and to read a stable value so I think this is not an issue.
2. See explanation from J-R! Some mode draws more power, so the battery goes suddenly to a lower voltage. Happens only when the battery is getting close to the treshold level. The exact value depends on the battery type, and temperature.

3. The Brymens switch is rather too stiff to get it accidentaly betwen position. Now I tried it, it is indeed possible, but you really have to try it hard.

I would suggest to Brymen to actually make the switch be much lighter, it would feel better when not working in heavy gloves.

[2N3055]

3) Yes, I have had the issue with the Brymen selector switch ending up between positions.  Some years ago my BM235 did that very badly when I turned it off and somehow ended up between Off and AutoV.  I put it away for a while and some weeks later the plastic had malformed and the switch literally flopped in the breeze.  I reversed the process over another few weeks and that fixed it.

Since then, I have been taking apart my Brymen DMMs and adding a small amount of lubricant to specific areas of the selector switch mechanism. I also add a tiny amount of precision lube to the contacts on the PCB.  Between the two, the selector feels a lot nicer to me, but maybe that is personal preference.  Due to the short warranty and overseas shipping costs, I consider all my Brymen DMMs to be disposable.

I have BM525S and BM869S and you simply cannot put them between the positions, it snaps very positively into predefined positions...
I think your opinion is very judgmental, based on sample of one. I'm not saying it did not happen to you, but one is not a sample to make conclusions on. I have no experience with other models, though.

Also, shipping and such is a USA problem. In EU they are readily available and affordable.
Here Fluke is more expensive than in USA.

Price difference between new F87 and BM869S (that is feature vise closer to F287 minus the graph mode) is such that you can buy 2-3 BM869S here... That takes care of potential warranty issues. And in last few years I had BMs, they are going strong...
I consider them very good quality and excellent alternative to super expensive Fluke so far.

[J-R]

I have about 10 Brymen DMMs and about 10 Fluke DMMs.  I have taken both types apart to tinker with.  The Fluke selector switches feel superior to me, partially because they are larger and easier to grab, but also they generally just nicely and gently fall into position.  Personally, the 121GW selector switch is my favorite.

It's true that there is not really a systemic "problem" with the Brymen selector switch, but I'm not going to lie and not post my experience with the BM235!

[giosif]

Thank you all for your input!
I do appreciate it.

Trying to answer some of the points raised:
1. My FW version is 10 (also shown in the video I included with my original post).
2. With regards to the occasional delay in Diode mode, again, more of a slight nuisance rather than a significant issue.
3. About battery level indicator, I should have mentioned that my voltage level measurements were done with my bench power supply powering the meter.
   So, the different voltage levels I talk about are not due to the different meter functions drawing more energy than others.
   And my main "issue" with it is more related to the reliability of the readings for those measurements which do not display the low battery indicator (while others do).
   Said differently, if I turn the meter straight to DCV measurements and I do not see a low battery indicator showing, then I want to *know* I can trust the DCV readings the meter is giving (i.e. the readings could not have been impacted by a low battery level).
   Otherwise, this can be a safety hazard, in my opinion, unless Brymen comes out states they do this intentionally (i.e. they are confident the DCV readings are reliable even below 3.7V and down to 3.58V or so).
4. With respect to the rotary switch landing between functions, maybe I've been spoiled with the likes of Gossen and Fluke, where that just doesn't happen. Not in my experience, anyway.
   I've had similar incidents with some Agilent/Keysight DMMs but, even with those, not within the first few days of using them.
   In any case, I'll try to exercise the switch for a while as with normal use (i.e. without explicitly trying to land between functions) and see if I encounter the problem again.
   Maybe it was just bad timing with the first occurrence.

[mwb1100]

  Said differently, if I turn the meter straight to DCV measurements and I do not see a low battery indicator showing, then I want to *know* I can trust the DCV readings the meter is giving (i.e. the readings could not have been impacted by a low battery level).
   Otherwise, this can be a safety hazard, in my opinion, unless Brymen comes out states they do this intentionally (i.e. they are confident the DCV readings are reliable even below 3.7V and down to 3.58V or so).

I don't see a statement about this specific detail in the manual; in fact, I don't see any statement about low battery behavior other than the one you already pointed out: "Low Battery: Below approx. 3.7V".  So you will need to ask Brymen for such a statement if you haven't already.

Alternatively, you could experiment with reading known values at low battery levels to see if readings go bad before the meter dies (my hope would be that readings remain correct even when the low battery symbol is displayed until the meter actually powers off due to low battery voltage).

[giosif]

I don't see a statement about this specific detail in the manual; in fact, I don't see any statement about low battery behavior other than the one you already pointed out: "Low Battery: Below approx. 3.7V".  So you will need to ask Brymen for such a statement if you haven't already.

I've asked Brymen and the short version of their response is this behaviour is as intended.
I suggested they document this in the manual, so people know it's not a defect.

[Antrus]

Hi everyone. My bm789 stopped measuring temperature. Can anyone post the contents of 24cs04 on the board with the buttons? The calibration is stored there.