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.

[J-R]

The 500,000 count mode on the BM869s can win out over the BM789, for example 7V.  You lose a digit on both going up a range, but you can bring it back on the BM869s and it's going to be a usable digit.

The dual display on the BM869s is hard to beat, but on the flip side the BM789 has AutoV/LoZ and NCV detection.  Brymen just wants you to own both...

[joeqsmith]

Not being an electrician, I seldom use ACA, ACV, NCV or LowZ modes.  If I am looking at AC, it is normally some odd ball wave shape and I want the AC+DC with the split display.   Actually, I like meters that can show even more than two parameters on one screen just to save time.  Most likely I am using a scope.   Having that split display for temperature has proven to be very useful. 

Someone else had posted about the stability of the 500k mode and I had made a short video showing a few high res meters with a somewhat constant voltage applied.  It no doubt moves and has a few counts of noise but it has been good enough to spot some trends.     

[sonpul]

YulyPH
Thank you.

I am pleased with both the brightness and duration of the BM789 backlight.
But I always wanted to have a mode so that the backlight would turn on itself immediately and turn itself off after 15 minutes.
Any ideas on how to implement this?

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.

I have always said that the BM789 was created very well. What would you notice about the long backlight time, AutoHold, easy-to-read display and much more


joeqsmith
But in AC+DC mode, the main display shows the RMS calculation using the formula

And that's exactly what the BM789 displays.
BM869s should display the same thing. Calculation of RMS using the formula.
What do you want to see on the second display?
What do you even see on the second display ?
AC or DC or can you switch between AC and DC on the second display?

[joeqsmith]

joeqsmith
But in AC+DC mode, the main display shows the RMS calculation using the formula
(Attachment Link)
And that's exactly what the BM789 displays.
BM869s should display the same thing. Calculation of RMS using the formula.
What do you want to see on the second display?
What do you even see on the second display ?
AC or DC or can you switch between AC and DC on the second display?

Math isn't in question.   Nor is the fact that the 789 supports AC+DC (many don't and I have to calculate by hand). 

If I am looking at AC, it is normally some odd ball wave shape and I want the AC+DC with the split display.   Actually, I like meters that can show even more than two parameters on one screen just to save time.  Most likely I am using a scope.   Having that split display for temperature has proven to be very useful. 

BM869s will display DC and AC, or AC+DC and AC.   I have a few meter that will show AC, DC and AC+DC at the same time.   

[Fungus]

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).

I use an oscilloscope for anything "AC" that isn't mains voltage.

[YulyPH]

I am pleased with both the brightness and duration of the BM789 backlight.
But I always wanted to have a mode so that the backlight would turn on itself immediately and turn itself off after 15 minutes.
Any ideas on how to implement this?

I have always said that the BM789 was created very well. What would you notice about the long backlight time, AutoHold, easy-to-read display and much more

It's hard to read the display with light glare and awkward positions without backlight so I need always on backlight.
Implementing a custom pcb for the backlight is a possibility but the compact nature of the meter kinda limits what you can stick inside.
Even if you do implement a custom solution there needs to be a reset for the timer (reuse a push button but lose the functionality of the meter for that button) otherwise you need to turn off/on the meter every 15 minutes.
The simplest solution is to have always on display with limited current. Even with 500R resistors there isn't much of a difference in backlight.

The quality of the display in BM789 is good and exactly the same as BM869s but with bigger digits. The display on BM829s looks kinda bad compared to the other two. All of them lose in top viewing angle.
Auto hold is useless on fluctuating mains but I guess any fluctuating voltage source (It jumps all over the place).
I do mains work on occasion so the live finder is quite useful as in my country mains wires don't have a fixed position for live/neutral in the sockets or even a specific color for the wires  .
Love brymen meters for having DC and AC low-z as it is very useful for discharging caps and detecting devices that have a bit of leakage (you don't need custom value resistances).
Also the speed of the BM789 is unlike anything I ever had the pleasure (or not  ) of using.
You might think BM869s is slow but it is actually second in speed.
BM829s was the fastest I experienced but with the above 2 it takes thinks to another level.

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).

I use an oscilloscope for anything "AC" that isn't mains voltage.

I also use a scope for visualizing the waveform even on mains (battery powered scope) but it takes time to boot up the scope and sometimes you may need a quick value to see that it works (smps power supplies for example)

Dual display becomes irrelevant with two meters sooo anyone wana trade a BM789 for my BM869s  ?

[J-R]

A use case can get specific enough to make one DMM an obvious choice over the other.  But I'd maintain that the BM869s is better for bench use in general.  Dual display and IR interface for starters.  Also, the calibration procedure is known, so you can really dial in the 500,000 count modes.  NCV, AutoV and Low Z are not typical on the bench, more household/industrial.  Anything where the frequency performance matters should go to the scope.

When away from the bench, those features really are handy, so the BM789 is easily the winner.  Although, some of UEi's DMMs with Bluetooth have been handy.

[EEVblog]

A use case can get specific enough to make one DMM an obvious choice over the other.  But I'd maintain that the BM869s is better for bench use in general.  Dual display and IR interface for starters.  Also, the calibration procedure is known, so you can really dial in the 500,000 count modes.  NCV, AutoV and Low Z are not typical on the bench, more household/industrial.  Anything where the frequency performance matters should go to the scope.
When away from the bench, those features really are handy, so the BM789 is easily the winner.  Although, some of UEi's DMMs with Bluetooth have been handy.

The BM780 series is designed as a direct competitor to the Fluke 170 series. It's almost indentical in shape and look, and includes the more "electrical" features of NVC and LowZ.
The BM869 is clearly designed as a high end lab meter.
Nothing mysterious here at all, just basic market segmentation.

[J-R]

The feature set between the BM78x and Fluke 17x doesn't align well enough for me to believe that it was "designed as a direct competitor".  The BM235 matches better.  It seems more likely that marketing wanted a story to tell and to be able to say "Fluke" during presentations.

[YulyPH]

Bench use, so what exactly does this mean for you ? For me it's troubleshooting, improving stuff,  basic experimentation and I guess for many more.
I do watch quite a bit of youtube channels and apart from learning channels I really don't see anyone have a need for PC communication/logging.
Some even use basic bottom of the barrel meters because they need a quick value then move on with there lives.
I you mean lab use then that is another thing entirely and BM869s might be just a starter pack.

People here are starting to agree that the scope is better for AC so what is left for dual display meters ?
Diode, continuity, and DC don't need dual display, maybe capacitance for ESR but I don't see any DMM have this feature.
Don't get me wrong I would like a display with as much info as possible but if it means compromising on other features than I take the single display.

Considering low-z a feature for electricians is just wrong.
You wouldn't want an electrician to work on your electronics.
I have interacted with many electricians and none of them had a meter with low-z or even know what to do with it.
Electricians like stick meters with a few leds because a number on a screen is to much and I agree with them, measuring voltage thousands of times a day becomes irrelevant if it's 220 or 230.