Brymen BM789

[joeqsmith]

Showing the Radio Shack clamp attached to the BM789.   I bought a Kline tools PN 69409 line splitter for a debunk video I made.  I am using the 10X side of the splitter.   

First I tried it with a simple light bulb.  The Kill-A-Watt EZ measures 0.48A.   This is a standard filament bulb so PF=1.   The BM789 measures 2.172mA.   The probe is 1mA = 2A.   So 2.172*2/10X = 434.4mA   

Next I tried it with my heat gun.  Again, it's a resistive load so the power factor is one.   The Kill-A-Watt EZ measures 3.72 Amps.   The BM789 measures 17.447mA.   Again 17.447 * 2/10 = 3.4894A.   

I'm not sure how accurate the Kill A Watt, meter or probe are.  The probe is +/-0.6A at 50/60Hz for 1-2A.  They show no data below 1A.  But 600mA of error on a 1A signal seems suspect.  We are doing much better than that.

+/-(4% + 1A) at 50/60Hz for 2-300A.   At the 3.5A, again we are much tighter.   

[J-R]

Curious, does anyone know if there's an accessory that would allow me to use a BM786 or BM789 similar to a clamping multimeter?

I understand there's an Electrical Field detection feature already available but it would be nice if there was a clamp I could attach to the multimeter's inputs to have it estimate the current in a wire, instead of buying a whole new multimeter just for the clamping function.

To start, you could consider various accessory clamps from Fluke and AEMC (Chauvin Arnoux), such as the Fluke Y8100 and 80i series, and AEMC SL2xx series (and Fluke and AEMC in general).

Also, there is some overlap in this area between DMMs and oscilloscopes.  Converting from BNC to banana jacks (or vice versa) is trivial.

However, despite having the PDI CA60 and some others, for portable DMM use I can't say it's worth it.  For the money and size/weight of the current clamp accessory, you could simply buy an entire clamp DMM and carry that in addition (or instead).  For the compact form factor, there is the famous Uni-T UT-210 series, the Brymen 03x series and many others.  Which to choose will come down to features and range/accuracy requirements.

[TomKatt]

However, despite having the PDI CA60 and some others, for portable DMM use I can't say it's worth it.  For the money and size/weight of the current clamp accessory, you could simply buy an entire clamp DMM and carry that in addition (or instead).  For the compact form factor, there is the famous Uni-T UT-210 series, the Brymen 03x series and many others.  Which to choose will come down to features and range/accuracy requirements.

That’s an excellent point - while these products do exist, it’s more cost efficient to just purchase a clamp meter.  Plus, they eliminate any conversion calculations by displaying the actual current.

[Astray]

Thank you guys for the info about the clamp!

Also I made a discovery concerning the BM786 and BM789 and made another post about it that might be of interest to some.

[sonpul]

Greetings to all. Question.

What is this pictogram (((D)))  and why is it there?

[BillyO]

It's not mentioned in the manual and I can't get it to come on, but I do see it there when I first turn it on.  What did you do to get it to come on?

[sonpul]

Set
VAC VFD  ;  ~Hz ;   REC 

An icon (((D))) will appear. You can leave Hz, leave VFD measurement, leave REC while remaining on VAC. The icon will remain displayed until you turn the selector.

[TomKatt]

Data (logging) ?

[sonpul]

Via bluetooth? Which was planned, but never appeared. It looks more like a sound symbol, a signal symbol.

[BillyO]

Set
VAC VFD  ;  ~Hz ;   REC 

An icon (((D))) will appear. You can leave Hz, leave VFD measurement, leave REC while remaining on VAC. The icon will remain displayed until you turn the selector.

That works.  Hmm, most likely something only partially implemented.

[EEVblog]

Via bluetooth? Which was planned, but never appeared. It looks more like a sound symbol, a signal symbol.

Yes, bluetooth was planned and they promised it but it never happened 

[YulyPH]

Had my brand new BM789 (from welectron with dakks calibration) for a week and I just want to share some info.
Firmware version is 13 so I guess they are still making improvements.
BM869s seems like a mistake as BM789 is better for AC voltage (more accurate voltage up to 100kHz - both meters go higher than that) and the readings are way faster (BM869s needs a few seconds to stabilize).
BM869s has the edge only in AC current but BM789 is not that far off, even if the datasheet lists only 3kHz it goes almost as high as BM869s.

I strongly recommend lubing the rotary switch as it's quite bad feeling out of the box. Super lube works perfectly.

Now for the those that like to compare backlight duration.
Every DMM that I owned switched the backlight throw a transistor so you could replace it with a resistor to limit the current and have the battery last longer with always on backlight.
Why do Brymen meters have backlights as bright as a flashlight ? If I want a flashlight I don't use a DMM  .
The BM789 is a bit special as the backlight is connected directly to the battery so it's not going throw the rotary switch.
The only way to have always on backlight is to get a voltage to the base of the transistor that is switched from the rotary switch (luckily there is a 3.5V track next to the transistor base track).
The mod can be done without removing the screen (just the plastic that holds the screen and backlight board then remove the backlight board with care) and is doable on the front or the back of the meter (I recommend cutting the transistor base trace and attach it to the 3.5V rail).
Anyway, around 60mA with default 150R resistors (R57, R58 and R84) and 17mA with 500R resistors (the result is more than enough backlight).
Even with good environment lighting the backlight makes the screen more readable.
Maybe one day Brymen will copy Uni-t (UT622 LCR meter with color screen and backlight adjustable from keys is just perfect or maybe UNI-T UT181 but I don't own one to be sure the screen is good).

[joeqsmith]

...BM869s seems like a mistake as BM789 is better for AC voltage (more accurate voltage up to 100kHz - both meters go higher than that) ...

BM869s supports logging, dual display, and while a few claim the 500k count is a gimmick, I have used it to hunt problems. 

I suggest buying the tools that fit your personal needs.  The only mistake is not doing your homework. 

[YulyPH]

BM869s supports logging, dual display, and while a few claim the 500k count is a gimmick, I have used it to hunt problems. 

I suggest buying the tools that fit your personal needs.  The only mistake is not doing your homework. 

Your right, and here we are talking about portable DMM's that are general purpose meters.
The 500k count is considered a gimmick because it's useless without measurement precision and stability.
The BM789 has the extra digit for frequency in contrast to BM869s extra digit for DC voltage.
BM869s and BM789 are above budget toy meters but at the same time they are not lab grade (maybe entry level).
As long as you don't need data logging the BM789 seems the better one as a general purpose meter.
And this was the answer that I was searching for that no one seemed to give.
Even ChatGPT says that BM869s has better accuracy with more features and the BM789 is the budget option 
Both calibrated and purchased a week apart from each other on DC they agree and for AC voltage the BM789 is way better.
Had to get them both to reach this conclusion.

[joeqsmith]

...
The 500k count is considered a gimmick because it's useless without measurement precision and stability.
...

I was once told there was never a reason to measure anything beyond 60Hz.   In many cases, I am looking for a relative change only.  Obviously your use case is different.  Not to suggest your statement is wrong but that we all have different requirements.