Brymen BM789 continuity tester response

[slavoy]

I'm currently using the Sanwa PC7000, and I am considering switching to the Brymen BM789. I'm particularly interested in the continuity tester's speed in this multimeter. In the Sanwa, the continuity measurement is the fastest I have seen, practically without any limitations with no latching. It responds almost instantly, and the buzzer's operating speed goes into kHz. I love it, and I really need it in my next multimeter. Has anyone conducted such tests for the BM789 with a signal generator?

[shapirus]

The manual says:

Response time < 100μs

The BM869s (which I think is built on the same platform as your Sanwa) manual says the same, so I guess it's safe to say that the 789 is not worse.

[joeqsmith]

In the Sanwa, the continuity measurement is the fastest I have seen, practically without any limitations with no latching.

You never state how fast is fast and for all I know, your Sanwa may be the only meter you have seen.  So here's my low cost UNI-T UT90A in action.  Is your Sanwa this fast?

[shapirus]

Lol, challenge accepted.

Direct feed from the headphone jack into the meter. I believe the audio quality could be improved by feeding it into a comparator that compares the signal against an adjustable reference voltage and then using its output to control a mosfet switch, whose resistance would be measured by the meter, but that would need more time. Besides, this track doesn't really sound all that better with normal speakers anyway

(once again, I believe this is essentially the same meter as the mentioned Sanwa)




That Uni-T is impressive though. I didn't know they actually had good continuity response.

[shapirus]

I believe the audio quality could be improved

...and indeed it can!

It requires two things: a) a signal polarity detector to turn on a switch when the wave is positive (or negative, doesn't matter) and off when otherwise; b) a high-pass input filter with cutoff frequency around ~2-2.5 KHz, close to the buzzer's own frequency. Maybe a preamp would also be helpful, since I found that increasing volume on the music output side helps, and on top of that filtering by signal level (by raising the polarity detector's threshold) to prevent low-volume component and noise from activating the buzzer.

Compressed recordings (I'm looking at you, metallica!) should sound better than those with high DR :)

As silly and funny as it is, it creates food for thought: think and experiment on how to produce multi-frequency sound with a mono-frequency buzzer, how to make it sound better, and how to design a respective circuit.

This reminds me of those old attempts of producing DAC-like sounds on the dumb mono-frequency PC speaker of early PCs when a proper sound card was a rare animal and cost a fortune. That sounded better, though, than my DMM :).

[joeqsmith]

I had a filter, comparitor, one-shot that I put together on one of those white plug-in bread boards that from what a few people on this forum suggest never use.   It wasn't worth building up something more permanent and was pulled apart that same day. 

[shapirus]

I had a filter, comparitor, one-shot that I put together on one of those white plug-in bread boards that from what a few people on this forum suggest never use.   It wasn't worth building up something more permanent and was pulled apart that same day.

Same here. Filter, op amp as comparator, 2N7000 as switch. Might have used an actual open collector comparator, I guess, but I had an LM358 within reach. The circuit even has a dual supply for the op amp made with a zener diode in parallel with a cap to provide reference ground (which can also be used as the threshold reference). Quick and dirty, and those solderless breadboards are super convenient and work just fine as long as you don't need high currents, fast edges or MHz frequencies.

[Fungus]

the continuity measurement is the fastest I have seen, practically without any limitations with no latching. It responds almost instantly

"Almost"? 

Get a Brymen and you can remove that word.

[shapirus]

Get a Brymen and you can remove that word.

This Sanwa is identical to BM869s in this regard (and almost any other): https://youtu.be/hbhNFL9ArbI?t=717, around 11:55.

So basically the original question can be rephrased like this: is BM789 not worse than BM869s with regards to the continuity buzzer response time?

[joeqsmith]

... those solderless breadboards are super convenient and work just fine as long as you don't need high currents, fast edges or MHz frequencies.

I think it was comments like yours that was the catalyst for member BreakingOhmsLaw to challenge the community. 
https://www.eevblog.com/forum/projects/challenge-thread-the-fastest-breadboard-oscillator-on-the-mudball/

A few second video documenting my final attempt: 

[mwb1100]

Comparing the functionality and the specs of the Sanwa PC7000 with the Brymen BM86x it's clear that the PC7000 is more or less a BM867s with a temperature measurement added, VFD (low pass filter) added and mostly similar but sometimes slightly better specs.  Another way to look at it is: it's a BM869s with only one temperature measurement instead of two and slightly worse (BM867-ish) specs.

I'll eat my Harbor Freight freebie if Brymen isn't the OEM.

One curious thing about the PC7000 is that the backlight only stays on for about 15 seconds - which is shorter than the ~30 seconds on original BM869s.  Brymen has since bumped the backlight timeout on the BM86x to about 4 1/2 minutes.  I find short backlight timeouts immensely annoying.

Additionally, the Sanwa PC720M is a Brymen BM525s with only one temp measurement instead of two.  Sanwa PC700/PC710 are from the Brymen BM82x series - I haven't looked closely enough at the specs to be certain about this PC700/PC710 claim, but it sure looks like a duck.

As I've said somewhere else (I think it was joeqsmith's favorite multimeter reviewer  ): I like Sanwa's look better than Brymen's, but not enough to pay Sanwa's premium over the Brymen prices.

To make this post a little more on topic, I have several Brymen meters and the continuity on each of them works fast enough that none are annoying to me, and they are subjectively as fast or faster than any other meter I've personally tried.  But I can't say whether they are quantitatively top-of-class.

[J-R]

I took a cursory look at the Sanwa PC7000 internals and compared it to the BM86x internals and they are quite different.  Specifically the Sanwa has a separate input jack PCB as well as a daughterboard for the IR.  Yes, the Sanwa clearly has a BTC (Brymen) chip in it, though.  I would suspect they mostly kept the circuit design but changed the layout because of various reasons.

References:

https://lygte-info.dk/review/DMMBrymen%20BM869s%20UK.html

[EEVblog]

I took a cursory look at the Sanwa PC7000 internals and compared it to the BM86x internals and they are quite different.  Specifically the Sanwa has a separate input jack PCB as well as a daughterboard for the IR.  Yes, the Sanwa clearly has a BTC (Brymen) chip in it, though.  I would suspect they mostly kept the circuit design but changed the layout because of various reasons.

Very interesting. I wonder if Sanwa designed it and just used Brymen's chipset, or if they contracted out the design to Brymen.

[Fungus]

One curious thing about the PC7000 is that the backlight only stays on for about 15 seconds - which is shorter than the ~30 seconds on original BM869s.  Brymen has since bumped the backlight timeout on the BM86x to about 4 1/2 minutes.  I find short backlight timeouts immensely annoying.

They claim it's to save our batteries.

The thing I don't understand is that Brymens have "intelligent APO" (to prevent auto-power-off if you're actively using the meter) but they can't figure out how to implement auto-backlight.

Why can't the backlight just be dim when the screen is showing zeros for a few seconds?

[Panter72]

Hi guys!

What is happening with SANWA?
I`ve based my workshop on their DMM`s for two decades now. Most used instruments are PC5000 and later PC5000a DMM`s. 
I use them daily and I love them and ttrust them with my life. There are a couple more but not USB connectable.

What is bothering me? I`ve also purchased a PC-link, and later PC-link+ logging software, set up some sensor and transducer calibration curves in it and, a couple of years ago, it gave up on me, saying that the licence had expired, and I`ve bought those fair and square.
First, when I`ve bought the second PC5000a (previous was 5000 model, no a`s) those would not work together on a same software?! Those instruments were bought just a couple of years apart.  Now, they do not support these instruments on their PC7 new software. I wrote to them, and got nothing. Also, I`ve asked to extend my licence, pay for it the second time...

NO ANSWER AT ALL!!!

I relly like the PC7000 but I`m not buying it!
Nope!

To base myself on a fluke or, God forbid, Gossen, would cost an arm and a leg.

Does anybody have any idea, since the chipsets should be the same ... would Brymen software work on old SANWA`s?

[TomKatt]

Personally, I love the speed and visual indicator on Dave's Brymen BM235 meter.  I've got a Greenlee DM820A (rebadged BM827s?) and it's nearly as quick, but I think the BM235 is quicker.  And the flashing light really helps.

[slavoy]

I relly like the PC7000 but I`m not buying it!
Nope!

To base myself on a fluke or, God forbid, Gossen, would cost an arm and a leg.

Does anybody have any idea, since the chipsets should be the same ... would Brymen software work on old SANWA`s?

I would gladly buy 5000a if they were still production. It was my first choice meter. Thats how I got the PC7000 several years ago, advertised as a 5000a successor.
I got no complains about the quality and accuracy. But I wouldn't buy it again today. It just got too expensive, the meter and accessories. More than $100, somewhere even $135 for a stupid usb cable is ridiculous.
Anyway, the cables work interchangeably between Sanwa and Brymen. As for the software Im not sure but chances are high that it will work with both meters.

[coromonadalix]

war on the continuity,  that's a first  loll

fluke 189 are very fast, and i love the fact they could screech while sliding probes against the other   ... 

and yes  accessories got damn expensive for many brands ....

[Fungus]

The absolute best continuity tester is the Aneng AN9205A. You can get one delivered for about $6-7.

eg. https://www.aliexpress.com/item/4001091479454.html

It's as fast as anything else I own (eg. BM857s, Fluke 8060A) and has a really bright LED for continuity.

(nb. A separate LED on the front of the meter)

discussion: https://www.eevblog.com/forum/testgear/conductivity-tester/msg4977931/#msg4977931

The PCB inside is small, I'm sure one could be hacked down into a custom "continuity tester" box.

[shapirus]

and i love the fact they could screech while sliding probes against the other   ... 

that's actually a killer feature (which the brymens have too). every continuity tester must be like this.
I have no idea who and why would in their mind prefer the painfully slow, stupid, non-informative latched response.

[BeBuLamar]

I have the Fluke 189 and I don't find it's continuity feature is anything special. Just the beep doesn't sound good to me.

[slavoy]

war on the continuity,  that's a first  loll

fluke 189 are very fast

Meh... latched Flukes... ruled out right from the start xD
//That's why I will never buy one (aside from the price)

[coromonadalix]

eh  i wont argue  loll 

some love em some hate em, as many brands out there ...  find what you love,  hate the others  loll

[nctnico]

and i love the fact they could screech while sliding probes against the other   ... 

that's actually a killer feature (which the brymens have too). every continuity tester must be like this.
I have no idea who and why would in their mind prefer the painfully slow, stupid, non-informative latched response.

I agree. For me continuity must be instant otherwise I start to wonder whether the probes are plugged in OR which one of the past 5 points I tested actually had a short. In bench DMMs it gets even worse compared to handhelds. I've been looking at a whole bunch of these (including the ones from the A-brands!) and so far I have found only two with instant continuity: VC8145 and UNI-T UT8805E.

[EEVblog]

I agree. For me continuity must be instant otherwise I start to wonder whether the probes are plugged in OR which one of the past 5 points I tested actually had a short. In bench DMMs it gets even worse compared to handhelds. I've been looking at a whole bunch of these (including the ones from the A-brands!) and so far I have found only two with instant continuity: VC8145 and UNI-T UT8805E.

That's because bench meters usually do not use a dedicated multimeter chipset that has an optimised continuity function. It traditionally just uses the high resolution dual slope integrator and implements a software continuity function.
Newer ones are better:
The Keithley DMM7510 is instant and latched, but it's got this weird buzzer type sound which is kinda strange.
The Keysight 34470 is also instant and again latched and has a much nicer tone than the keithley.