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BM789 continuity behaviour
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giosif:
@Electro Fan: That was a (long, but) interesting read. :-)
And I agree that, without more in-depth investigation, it is hard to tell what the main contributing factor(s) to this behaviour is/are.

This said, mine is more of a layman's perspective on the matter: in practice, the continuity mode on the BM789 is less useful than that on most decently-fast meters (e.g. 121GW, BM257s, Fluke 87V, Fluke 187/189, etc.).
And just to prove what I mean (and what actually compelled me to start this thread in the first place), I made a recording of me using the BM789 in continuity mode on a given board (the video also shows me using the BM257s, with no spurious beeps present):
https://youtu.be/ZibMm3JXq7I
I suggest paying particular attention to the 0:30 mark in the video, when I am probing a denser area on the board.
As you can see, the amount of spurious beeps in quick succession makes one unable to determine if there is continuity or not, unless one keeps the probe in a location for longer.

Also, based on the response I received from Brymen (basically, the same as LuisBe's), I am to believe this is intentional for "professional applications" where sub-100μs response time for continuity is needed.
I wonder what real-life usage scenarios for a handheld multimeter would require such crazy-fast response time (as opposed to, say, the 15ms for the BM235).
Is a human even able to tell the difference between the two response times in any given scenario?
Also, if the spurious beeps are a consequence of this fast response time, don't they actually negate the value of this feature?

In my latest response to Brymen, I queried if it may be possible to implement (through a FW update) an option for the user to switch between "crazy fast" and "decent fast" response times.
I will report any response I get.
joeqsmith:
I tried with a 150pF then a 300pF and could not get mine to trigger.    From my spreadsheet, the short circuit detection resistance was as high as 270 ohms.   The BM235 measured 152 ohms.  The BM839, 110 ohms.   869s, 94 ohms.   From the meters I have looked at,  in general Brymen seems to set this resistance higher than other brands.  I suspect this is why you are seeing the blips.  Agree that this would slow you down when tracing out a board. 
tautech:
They can't all play Van Halen.   :P

Joe you have a standardized continuity test using an AWG to sense both min pulse width and max frequency which I have used too testing bench meters.  :-+
joeqsmith:
I just didn't see the whole touching the leads thing as being very useful.  Now if we could get some sort of standards for low frequency magnetic interference, low energy transient, chemical compatibility and switch life,  maybe we would have something.   
giosif:
Hi,

Just to provide an update that Brymen did eventually get back to me with an update on changing the response time of the BM789 for continuity mode.
And the change is a hardware modification (which Brymen called a "hack") - using the attached picture as reference:

* R17 & C9 on the factory BM789 are:
  R17: soldered with a 0Ω resistor
  C9: spare (without any capacitor soldered)
* The modification consists of:
   R17: replace the 0Ω resistor with a 25kΩ one
   C9: install a 0.1μF capacitorI have implemented the above modification on my meter and I can confirm the continuity behaviour is now similar to that of other meters mentioned here (e.g. BM257s, 121GW).  :-+
I have asked Brymen and they confirmed this change impacts only the continuity measurements on the meter and no other function.

Hats off to Brymen for looking into this and coming up with a resolution.
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