New EEVblog BM786 Multimeter

[bdunham7]

While I agree with the premise, I can't shake the feeling that something is amiss if this should be considered a normal behaviour of the BM78x series. I have been through many multimeters of several brands and the RM102Pro was the only one that gave me random beeps that I can recall. And I have used and tested many crap and excellent models/brands.

If you set up a test rig with a capacitor and a bleed resistor well above the continuity threshold, say 10k, and then test continuity with different capacitors and different meters you should find that all of the meters will emit a beep, squeak or chirp if you go above a certain capacitor size.  The capacitor size at which you first hear a sound will vary quite a bit from meter to meter.  Those meters that respond to the smaller capacitors will also be the ones that catch a short as you scan a probe down a row of connectors.  AFAIK, there's no easy way around that tradeoff.  One other variable would be the continuity threshold--it would make some difference it were unusually high.  The BM786 says "100 to 420ohms".

Edit:  There's one more variable--test current--and for the BM786 it is fairly low at ~350uA.  That would also make it more sensitive to capacitors.

[tautech]

I had this on an ultra-cheap Richmeters RM102Pro (Aneng 113D). It pissed me off.

With Brymen, it might be a random issue, although having a fellow youtuber go through this as well is concerning.

Why ?

Just like any instrument learn to know what it does under various usage conditions and adapt to it. You can't have super fast continuity and it not also react to probing across a capacitance.

The Kaise moving coil meter I got for my 21st would always display a cap charging and for really stuffed ones display if they were leaking too. Way back in the 70's we used this behavior to good effect before the days of cap testers.

[Fungus]

i never had this issue with a Amprobe AM-570 that got stolen.
or my cheap UNI-T UT61E that i replace for this BM786

Maybe they had slower continuity function.

As others have said, if you probe a discharged capacitor it will appear as a short-circuit for a fraction of a second. That's electronics.

If a meter's continuity test is fast then it will beep. If it's slower, it won't.

nb. It will also depend on the meter's continuity test voltage, the size of the capacitor, the ESR of the capacitor, etc.

OTOH the meter might be defective. Find the minimum resistance it beeps on, eg. with a potentiometer and measure that resistance. Does it match what it says in the manual?

[rsjsouza]

I had this on an ultra-cheap Richmeters RM102Pro (Aneng 113D). It pissed me off.
With Brymen, it might be a random issue, although having a fellow youtuber go through this as well is concerning. Perhaps it is a variability of part tolerances?

The Brymen is a fast responding meter, and there is always variability in the detection threshold between meters. No two model meters will be idential here is you are dealing with capacitive loads.

While I agree with the premise, I can't shake the feeling that something is amiss if this should be considered a normal behaviour of the BM78x series. I have been through many multimeters of several brands and the RM102Pro was the only one that gave me random beeps that I can recall. And I have used and tested many crap and excellent models/brands.

There is no way this can be verified without proper testing under controlled repeatable conditions.
I'm not saying it's not a thing, but no one else has reported this, and I am not in a position to test this at present.
Do you have the BM786 and are getting the same problem?
Also, and issue on the Bm786 will almost certainly be present on the other models in that series.

I don't have the BM786 (I wish), but reading other's comments I suspect I misunderstood the original problem

My RM102Pro had very occasional beeps if you shook the probes flailing in the air or if only one of them touched a circuit. That is what I read from the original issue and that is a problem in on itself with the meter. If probing and the occasional beep happens, I fully agree the influence of the circuit is to blame here.

If you set up a test rig with a capacitor and a bleed resistor (...)

(...)You can't have super fast continuity and it not also react to probing across a capacitance.(...)

(...)As others have said, if you probe a discharged capacitor it will appear as a short-circuit for a fraction of a second. That's electronics.(...)

Indeed. I might have misread the original problem.

[Meter Deter]

so let me get this straight. its normal to give false beeps?

for me to avoid false beeps i need to drain the capacitors first?

[tautech]

so let me get this straight. its normal to give false beeps?

for me to avoid false beeps i need to drain the capacitors first?

NO !
Beeps represent charge going into caps until the meters continuity threshold is no longer met.

Fast continuity meters have this effect however slow POS continuity won't.
For some meters and bench ones in particular you can adjust thresholds to to not have this behavior however when you want/need best performance you need to reset it again.

[EEVblog]

so let me get this straight. its normal to give false beeps?
for me to avoid false beeps i need to drain the capacitors first?

Capacitors appear as a short circuit briefly if they are discharged and you apply a voltage to them. If your meter is fast enough and provides enough charge to appear as a low enough resistance then it will beep. That would be expected and normal.
If the capacitor are already charged then that changes the equation and makes it all more complicated.

[Brumby]

Capacitors appear as a short circuit briefly if they are discharged and you apply a voltage to them. If your meter is fast enough and provides enough charge to appear as a low enough resistance then it will beep. That would be expected and normal.

Exactly this.  It's simply the physics involved.

If you want to avoid such "false beeps" you would need the meter to delay the beep until any capacitors involved get a bit of charge in them (from the meter current through the probes) - but how long would you wait?  The time would vary with various values of capacitance.

However, such a delay would annoy the heck out of anyone and everyone I have encountered.  It's not the sort of "feature" that would appeal at all.  (Just witness Dave's reaction when he checks out meters.)

You are far better off having a fast response meter and being aware of the circuitry you are probing to correctly interpret any beeps.  Sometimes all that is required is that you re-check the probing point and/or look at the resistance being displayed.  If it's going up, then you've got capacitance.

[EEVblog]

If you want to avoid such "false beeps" you would need the meter to delay the beep until any capacitors involved get a bit of charge in them (from the meter current through the probes) - but how long would you wait?  The time would vary with various values of capacitance.

However, such a delay would annoy the heck out of anyone and everyone I have encountered.  It's not the sort of "feature" that would appeal at all.  (Just witness Dave's reaction when he checks out meters.)

You are far better off having a fast response meter and being aware of the circuitry you are probing to correctly interpret any beeps.  Sometimes all that is required is that you re-check the probing point and/or look at the resistance being displayed.  If it's going up, then you've got capacitance.

Yes, it's standard continuity troubleshooting procedure. False negatives (missed connections) are undesirable, that's why people value fast latched continuity modes. If you get a beep you then keep the probes on for longer and read the value and determine if it's a legit connection or a false positive due to a cap or some other in-circuit component.
Having a slow continuity tester and missing beeps can mean it takes way longer to find what you are looking for as you might have to do another entire pass at an even slower rate.

And having such a thing selectable/adjustable might sound like a good solution, but then you have to check it before you start and decide what mode you want (often you won't know unless you start and get some results), and then you also risk forgetting to do that and thinking you are in a mode you aren't.

[bdunham7]

And having such a thing selectable/adjustable might sound like a good solution, but then you have to check it before you start and decide what mode you want (often you won't know unless you start and get some results), and then you also risk forgetting to do that and thinking you are in a mode you aren't.

Having the threshold be precise and selectable is very handy, but I'm not feeling any urge to adjust the response time or test current.

[EEVblog]

And having such a thing selectable/adjustable might sound like a good solution, but then you have to check it before you start and decide what mode you want (often you won't know unless you start and get some results), and then you also risk forgetting to do that and thinking you are in a mode you aren't.

Having the threshold be precise and selectable is very handy, but I'm not feeling any urge to adjust the response time or test current.

I think the Keysight meter allows you to adjust the threshold. The 121GW also allows threshold adjustment.
Never heard of a meter that allows response time adjust.

[floobydust]

I have seen multimeters malfunction doing Ohms measurement on a DC rail with capacitance and semiconductors present.

Starting at the lowest Ohms range, beep and charging happens until the multimeter upranges with the corresponding lower compliance current then causing the capacitor's voltage to start dropping. This can also be aggravated due to semi's becoming biased on and current drain increases as the voltage goes up. It's a non-linear load. Auto-ranging will oscillate between ranges hunting all the time.

I believe the test current on the Brymen is quite low now at 0.3mA compared to 1-4mA on other multimeters. I just manual range to look for shorts.

[Neutrion]

Reading all this makes me wonder how come, that non of the manufacturers tried to solve this so far. I think it would be possible, even if not trivial.
The function could be called "True silence continuity function". Or ZEN buzzer.

Edit:

I just manual range to look for shorts.

How do you do that?

[EEVblog]

I've split out the Low Ohms discussion to it's own thread:
https://www.eevblog.com/forum/testgear/multimeters-with-low-ohms-function/

[RissViss]

Just wondering if you will be writing a manual for the BM786?
I found a pdf manual that Brymen made, but it is a mixed manual for three different models.

[EEVblog]

Just wondering if you will be writing a manual for the BM786?

If I get off my arse 

[Marde]

Hi Gang,
I wanted to get a case for my new BM786. I had intended on just getting a zippered soft case for it, so I started looking online. What I found was that many of the cases listed were not dimensionally compatible with it... <<quote snipped with scissors>>.
https://www.amazon.com/gp/product/B07VR3CB2N/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&th=1

Thank you for sharing your search & experience, for a BM786 case. I almost forgot I needed a case for mine, plus you saved me lots of shopping-around-time too. I just ordered the same case. Cheers!

[EEVblog]

Hi Gang,
I wanted to get a case for my new BM786. I had intended on just getting a zippered soft case for it, so I started looking online. What I found was that many of the cases listed were not dimensionally compatible with it... <<quote snipped with scissors>>.
https://www.amazon.com/gp/product/B07VR3CB2N/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&th=1

Thank you for sharing your search & experience, for a BM786 case. I almost forgot I needed a case for mine, plus you saved me lots of shopping-around-time too. I just ordered the same case. Cheers!

The BM786 is almost the exact same size and shape as the Fluke 70/170 series, so any case for those should work fine.

[Fungus]

If only Brymen made cases for their meters at non-ripoff prices:

https://brymen.eu/shop/softcase-for-brymen-bm5xx-bm8xx-bm9xx-series/

[J-R]

Brymen makes a carrying case specifically for the BM78x series.  It's about 1" narrower and 1/2" thinner than the BM8xx case.
https://www.welectron.com/Brymen-BMP-78x-Carrying-Pouch

[Marde]

Hi Gang,
I wanted to get a case for my new BM786. I had intended on just getting a zippered soft case for it, so I started looking online. What I found was that many of the cases listed were not dimensionally compatible with it... <<quote snipped with scissors>>.
https://www.amazon.com/gp/product/B07VR3CB2N/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&th=1

Thank you for sharing your search & experience, for a BM786 case. I almost forgot I needed a case for mine, plus you saved me lots of shopping-around-time too. I just ordered the same case. Cheers!

The BM786 is almost the exact same size and shape as the Fluke 70/170 series, so any case for those should work fine.

That might be true, however each case will be unique in its' own way AND some of those might not fit this meter very well. Reading the comments & seeing the picture posted by PinPassion, -it shows the BM786 fitting snug into that case, and it confirms this particular case works well for any 786 owner. Fluke 70/170 series (and aftermarket) sized cases might be a good-fit for the BM786, but that is a different discussion and that might also deserve a different thread inside this forum. If there is already a thread that talks about BM78x carry/storage cases, -I did not know, -please forgive me.

[Marde]

I can confirm, the post at #547 by PinPassion, is a perfect case for the BM786. The outer-most (pre-cut) foam fits into the case with the BM786 held-in snugly. The fit is perfect. The case lid pouch has plenty of room for the meter test leads + some of my most-used adapters too.  If you do not want storage space inside the case lid for some of your meter's extra stuff, you might not like this case. I am super happy with the Proster Case that PinPassion recommended. I bought this case via Amazon in the USA, -under $20.00. The included Magnetic Hanger Strap goes into my pile of un-needed junk.

[uboot]

I do believe this is for the optional bluetooth module.
Brymen said way back

We plan to just put Bluetooth capability on the PCB but leave it off for BM78x first generation models. Once we complete the software development, we will launch out BM78x with Bluetooth version models.

I asked then if it was possibble to at least make the processor output serial data or whatever so that users could retrofit their own module if needed. That would make it cool feature "hack". But it seems they didn't do it.
They memtioned a CYPRESS CYBLE-212006-01 module, but that pinout doesn't match, maybe a daughterboard?

Are there any news regarding this?

I'm pretty much torn between buying the BM786 or 789 vs BM869s and if the former had BT or USB, I was sold on it already.

The BM869s get's a bit pricey when bought together with the optional USB interface (even when chosing a custom-built interface like the one from my fellow Czech neighbor https://www.tindie.com/products/martind/brymen-867869-adapter-cable/) and the BM789 looks more decent in terms of specs and features and that's what's blocking me from just buying the BM869s.



EDIT: I also have a second question: the BM86x seems to be easy to calibrate - is there a similar procedure and calibration guide somewhere for the 78x like this one here https://www.jackenhack.com/calibrating-brymen-bm-series-multimeter/

[EEVblog]

I do believe this is for the optional bluetooth module.
Brymen said way back

We plan to just put Bluetooth capability on the PCB but leave it off for BM78x first generation models. Once we complete the software development, we will launch out BM78x with Bluetooth version models.

I asked then if it was possibble to at least make the processor output serial data or whatever so that users could retrofit their own module if needed. That would make it cool feature "hack". But it seems they didn't do it.
They memtioned a CYPRESS CYBLE-212006-01 module, but that pinout doesn't match, maybe a daughterboard?

Are there any news regarding this?

I'm pretty much torn between buying the BM786 or 789 vs BM869s and if the former had BT or USB, I was sold on it already.

Nope. I suspect they may have abanonded it.

[Antrus]

Hi all. I found a strange hybrid from a Brymen - Metrel MD 9055, Two displays. 60,000 counts are declared.