BM786 continuity beep not latched

[woox2k]

Hello!
I finally decided to stop buying random crappy meters and get annoyed by their multiple problems and purchased a BM786 meter. Everything seems to work but for some odd reason the continuity beep is not latched. First i thought that maybe i misremembered and this meter did not even have this feature but i have the same meter at work and its beep is nicely latched.
Is this a fault of some sort or just a setting i can toggle on and off with some button combinations? I would not want to hassle with warranty since i ordered it from quite far away...

[BeBuLamar]

What do you mean by latching? You want the beep to stay on even after the continuity is not there any more? If so I don't know of any meter that does that.

[woox2k]

What do you mean by latching? You want the beep to stay on even after the continuity is not there any more? If so I don't know of any meter that does that.

No, i mean that it behaves like the cheapest meters and doesn't have a well defined beep. With bad connection the beep sound is very scratchy.
Random EEVblog video i found that shows this: https://youtu.be/ZoeUgMFLyAw?si=MJ41OxVKK8Re_QXn&t=1808
At 30:08 that Elenco meter doesn't have a latched beep and this is the issue i'm having with my BM786.
29:35 (Amprobe) is an example of a latched beep, this is similar how the BM786 should behave, just without the huge delay.

It's not a huge dealbreaker but it worries me a bit since the exact same meter i have at work does not have this issue and the beep is nicely latched and quick.

[Manul]

I'm not familiar with the internals, but I'm guessing that on a modern multimeter latching must be controled in firmware? Or is it some hardware monostable type circuit? If it's firmware controlled, then I hardly see, how it can be broken. Maybe there is a latch duration setting and it's corrupted? Very strange indeed.

[woox2k]

Just for clarity i made a video showing this particular issue: https://drive.google.com/file/d/12fMtrt7vw-JQqA4WbSu3nWnJUhm-ETHO/view?usp=sharing
I did use the cheapest chinese probes for this test on purpose because it makes this issue more prominent. With original gold plated probes the issue is not that bad because they have much better contact.

[Doctorandus_P]

Just for clarity i made a video showing this particular issue: https://drive.google.com/file/d/12fMtrt7vw-JQqA4WbSu3nWnJUhm-ETHO/view?usp=sharing
I did use the cheapest chinese probes for this test on purpose because it makes this issue more prominent. With original gold plated probes the issue is not that bad because they have much better contact.

Buzzer not being latched is a good feature. It allows you to recognize bad (intermittent) connections by ear. Sure, the scratchy sound may be "annoying" to hear, but I prefer it because it has more information in it than a simple prolonged beep. What if you have a wiring harness with a broken wire that makes intermittent contact? Connecting my DMM to such a wire gives instant feedback about the connection while "massaging" the wiring harness to see If I can find the fault.

[BeBuLamar]

Just for clarity i made a video showing this particular issue: https://drive.google.com/file/d/12fMtrt7vw-JQqA4WbSu3nWnJUhm-ETHO/view?usp=sharing
I did use the cheapest chinese probes for this test on purpose because it makes this issue more prominent. With original gold plated probes the issue is not that bad because they have much better contact.

Buzzer not being latched is a good feature. It allows you to recognize bad (intermittent) connections by ear. Sure, the scratchy sound may be "annoying" to hear, but I prefer it because it has more information in it than a simple prolonged beep. What if you have a wiring harness with a broken wire that makes intermittent contact? Connecting my DMM to such a wire gives instant feedback about the connection while "massaging" the wiring harness to see If I can find the fault.

Yes and the continuity beeper is only useful for intermittent problem. Otherwise I use the resistance measurement.

[woox2k]

Buzzer not being latched is a good feature.

That might be true but it did worry me because this meter shouldn't have this "feature"! Not going to return it under warranty because of that but i would be interested to know what causes that issue. Is it a firmware thing where they just changed some parameters between revisions or something in hardware?
I don't even know how to check the firmware version on that meter. I kinda recall it being a thing but cannot find it in manual anymore...

[floobydust]

Fast continuity beep is a feature people want. It's not an "issue", it's deliberate. Instead of a sluggish beep that is useless for finding a bad connection.
Who needs a slow beep? Connection went open-circuit 200msec ago but still beeping? 

If you're not happy with it, send it back.

[donlisms]

It may also be good motivation to consider the cause(s) of the intermittent contact.  Something to think about. 

[J-R]

Buzzer not being latched is a good feature.

That might be true but it did worry me because this meter shouldn't have this "feature"! Not going to return it under warranty because of that but i would be interested to know what causes that issue. Is it a firmware thing where they just changed some parameters between revisions or something in hardware?
I don't even know how to check the firmware version on that meter. I kinda recall it being a thing but cannot find it in manual anymore...

Can't agree with any of the replies.  The continuity beeper on the BM78x is supposed to be latched.
Proof:
https://youtu.be/WuNLEQfudnw?t=990
https://youtu.be/Vd2PGLwPdhQ?t=669
https://youtu.be/YHuy2PYNq68?t=1458

However, it's possible Brymen made a change to the firmware without disclosing it, although I really doubt it.  You can view the firmware by holding the Delta (relative) key during power-on.

So I suspect your unit is faulty. When/where did you purchase it?

I also tested my BM789 FW version 05 (BM786 adjacent) and under no circumstances could I get it to be scratchy despite fully exploring the ~295 Ohm trigger point.  It either beeps or it doesn't.

[woox2k]

FW version shows up as 78611 (version 11 then?) Next time i'm at work i'll check the meter FW version there too. Nevermind, called them up and asked. It's 78607.
So there is significant difference between versions. Highly doubtful but maybe Brymen did mess up the beep timings with new version (mishaps like that do happen sometimes). Then again, maybe latching is done in hardware and i just happen to have some bad capacitor or something on the circuit board...

Both these meters are purchased from Welectron (Germany) Mine is few months old and one at work is couple of years old.

[floobydust]

The word "latches" is incorrect. It really is a (continuity) triggered one-shot (in firmware) that extends the beep, a pulse stretcher.
It looks like changes have been made to the F/W in the BM789 similar to what you are seeing: https://www.eevblog.com/forum/testgear/bm789-continuity-behaviour/25

[J-R]

The latching term is somewhat common.  It's even mentioned in one of the videos I linked.
The issue in the other thread isn't the scratching.
I would loop Dave in on this issue and get clarification on whether it's a conscious design change or an issue with that DMM that requires a warranty replacement.

[woox2k]

I would loop Dave in on this issue and get clarification on whether it's a conscious design change or an issue with that DMM that requires a warranty replacement.

Some explanation from Brymen would be perfect. I don't think i would hassle with sending it back to Germany either way but the whole point of this thread was to get some explanation to this, bit annoying but not dealbreaking, issue.

I should have bought 121GW instead! Silly me believing that getting a meter i had already used and liked would be best idea. Just my luck i guess... 

[EEVblog]

I finally decided to stop buying random crappy meters and get annoyed by their multiple problems and purchased a BM786 meter. Everything seems to work but for some odd reason the continuity beep is not latched. First i thought that maybe i misremembered and this meter did not even have this feature but i have the same meter at work and its beep is nicely latched.
Is this a fault of some sort or just a setting i can toggle on and off with some button combinations? I would not want to hassle with warranty since i ordered it from quite far away...

I'm
No one has ever complained that the BM786 does not have a "latched" buzzer.
It literally gives you one solid loud tone, and none of that "scatchy" noise, which is the definition of "latched" vs "unlatched".
Are you sure you not confusing it with the diode beep mode? (whcih is also "latched" but has a big delay)

[woox2k]

Are you sure you not confusing it with the diode beep mode? (whcih is also "latched" but has a big delay)

Thanks for taking your time checking this thread out!

Few posts down i posted a link to a video showing the issue i'm having. This is recorded by me showing this particular meter: https://drive.google.com/file/d/12fMtrt7vw-JQqA4WbSu3nWnJUhm-ETHO/view?usp=sharing
It is in continuity mode and it really does not latch. The sound is scratchy with intermittent contact!

[EEVblog]

FW version shows up as 78611 (version 11 then?) Next time i'm at work i'll check the meter FW version there too. Nevermind, called them up and asked. It's 78607.
So there is significant difference between versions. Highly doubtful but maybe Brymen did mess up the beep timings with new version (mishaps like that do happen sometimes). Then again, maybe latching is done in hardware and i just happen to have some bad capacitor or something on the circuit board...

Woah, I just took out a new stock 786 with 78611 firmware and sure enough it's a way faster latch than 78607 I normally use in the lab.
Have to go to the gym now, will shoot a comparison video when I get back.
I can make it be a bit "scratchy" with very lightly toughing probes, but it's still obviously "latched", it's just faster at the release time.

[EEVblog]

Few posts down i posted a link to a video showing the issue i'm having. This is recorded by me showing this particular meter: https://drive.google.com/file/d/12fMtrt7vw-JQqA4WbSu3nWnJUhm-ETHO/view?usp=sharing
It is in continuity mode and it really does not latch. The sound is scratchy with intermittent contact!

Your is going to be a bit worse because you are not using the gold plated probes.
I'll do a demo video in a few hours.

[woox2k]

Your is going to be a bit worse because you are not using the gold plated probes.

That was intentional to make my example more clear. With proper gold plated probes the issue is not so apparent but still possible to make "scratchy" sound by touching the probes very lightly. While it might be faster it's still a bit earsore to hear those scratches. When measuring real circuit boards the contact is rarely as good as two gold plated probes touching eachother. Initially i noticed this "odd behaviour" with original gold plated probes. I was probably biased though because i had already used BM786 quite a lot at work and knew how it should sound.

But it starts to seem that this is indeed intentional change by Brymen with v11 firmware... Interesting! I wonder what drove them making that change? The old "latch timing" was already fast enough to do "drag testing" to see grounded/shorted contacts. This one might be better in some corner cases but overall sounds bit cheap.... To a point i really thought this is a fault and inspired me to make this thread.

[floobydust]

Is this related to the BM786 electromagnetic buzzer issue? The bonehead that put it right on top at the xtal and sensitive ADC pins, which caused noise to get in, and I remember the fix was a metal shield to be put on the buzzer.
edit: https://www.eevblog.com/forum/testgear/new-eevblog-bm786-multimeter/msg3608153/#msg3608153
edit2: apparently I am wrong, the shield is for the magnet strap holder although I remember otherwise.

[woox2k]

Is this related to the BM786 electromagnetic buzzer issue?

Currently it seems to be a new setting in firmware, not in hardware. Let's wait until Dave has had time to investigate it. He did confirm that FW v11 meters have something differently configured. We don't know if the boards themselves have been significantly updated as well or it's all just in firmware. It being a firmware thing is kinda worse though, in that case there will not be a hacky workaround for people who prefer cleaner beep.

[EEVblog]

Yep, confirmed. 78611 is different.
I checked and Brymen didn't send me the 78611 firmware file, so I can't verify if the hardware makes a difference, but I'd be stunned if it did.

[J-R]

The metal shield was to prevent the Brymen magnetic hanger option from causing the speaker to be muted.

[EEVblog]

The metal shield was to prevent the Brymen magnetic hanger option from causing the speaker to be muted.

Correct. It didn't impact the measurements.