Author Topic: New EEVblog BM786 Multimeter  (Read 69432 times)

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rsjsouza

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Re: New EEVblog BM786 Multimeter
« Reply #75 on: October 25, 2020, 02:01:36 pm »
That's correct.  It's very slow in resistance with values over 10M, on the order of 10-15 seconds to settle with the 40M.  From the video, you can also see the 150pF took a fair bit of time but then so did the 100uF.   Part 2 will include a few more speed comparisons.
Ah, I got confused there. The 150pF on the Keysight was instantaneous (as with everything below 1uF) but the 100uF was about the same between the two.

BTW, I measured mine with a 100M resistor
Vbe - vídeo blog eletrônico http://videos.vbeletronico.com

Oh, the "whys" of the datasheets... The information is there not to be an axiomatic truth, but instead each speck of data must be slowly inhaled while carefully performing a deep search inside oneself to find the true metaphysical sense...

joeqsmith

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Re: New EEVblog BM786 Multimeter
« Reply #76 on: October 25, 2020, 03:08:14 pm »
The manual shows the high end for this meter is 60M.  They show a 0.1uA current for the 6M range and 0.01uA for the 60M range.

If you wanted some closer numbers to compare it with yours, just let me know the value and we can set it up with the counter and high speed camera.
Software, documentation and test reports for the low cost NanoVNA & V2 Plus 4 may be found here:
https://github.com/joeqsmith

rsjsouza

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Re: New EEVblog BM786 Multimeter
« Reply #77 on: October 28, 2020, 01:44:44 am »
The manual shows the high end for this meter is 60M.  They show a 0.1uA current for the 6M range and 0.01uA for the 60M range.

If you wanted some closer numbers to compare it with yours, just let me know the value and we can set it up with the counter and high speed camera.
Ah, no worries. I think the ballpark is accurate enough to expose how the two multimeters somewhat compare with each other in the capacitance and the ohms.
Vbe - vídeo blog eletrônico http://videos.vbeletronico.com

Oh, the "whys" of the datasheets... The information is there not to be an axiomatic truth, but instead each speck of data must be slowly inhaled while carefully performing a deep search inside oneself to find the true metaphysical sense...

joeqsmith

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Re: New EEVblog BM786 Multimeter
« Reply #78 on: October 28, 2020, 01:54:59 am »
No problem.  It may be a while so if you come up with something later, I'm fine with it.
Software, documentation and test reports for the low cost NanoVNA & V2 Plus 4 may be found here:
https://github.com/joeqsmith

wizard69

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Re: New EEVblog BM786 Multimeter
« Reply #79 on: October 28, 2020, 02:17:30 pm »
The first thing that catches my eye is that this new DMM has 60000 count instead of 500000 count like BM-867/869.

What is the reason to use less than 500000 count chipset for modern DMM?

The first thing that comes up when I see comments like this is how accurate are those 500,000 count hand held DMM's?

The second thing that comes to mind is how often do you really need to resolve to that many digits in a handheld.    If I'm about to calibrate something I will use a device (handheld or not) that is designed for the task at hand.   More importantly that device will be on some sort of calibration schedule.    Most DMM's of the handheld variety are seldom kept on a stringent cal program.   That is the case in the hobby world as well as the commercial world.

60,000 counts in a handheld device is a bit of a luxury as in many use cases you can get buy with 3-4 digits easy.   In fact sometimes you are better off with fewer digits.    Sometimes too much info is a bad thing.   By the way I'm not trying to say that high precision and high resolution is a bad thing in a handheld meter, just that for many users it really serves no purpose.

For example at work I'm involved in industrial systems under 600 VAC and similar for DC systems.   I can't ever remember needing to know the voltages on such systems beyond the first decimal point.   At lower control system voltages under 24 VDC you seldom need to know what power supplies are doing beyond the second decimal point.   It is only when you get involved in instrumentation that accuracy and resolution are important for calibration work, at that point you are working with traceable instruments anyways.   So 60,000 counts is more than good enough in this context.

Brumby

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Re: New EEVblog BM786 Multimeter
« Reply #80 on: October 28, 2020, 02:26:45 pm »
As has been mentioned before, accuracy to 5 or 6 digits is rarely needed on most people's bench - but 5 or 6 digits of resolution are often very useful.

For example - If I have a reading of 4.5678V and when I alter the circuit somehow, the reading becomes 4.5675, then I have a pretty good idea the voltage went down - just a little.  Sometimes, that's exactly the bit of information you need.  The absolute accuracy could be out by 10%, but the change will still be a valid observation.

Fungus

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Re: New EEVblog BM786 Multimeter
« Reply #81 on: October 28, 2020, 06:20:38 pm »
The first thing that catches my eye is that this new DMM has 60000 count instead of 500000 count like BM-867/869.

What is the reason to use less than 500000 count chipset for modern DMM?

Simple: Because even 6000 counts is 0.016% accuracy. Supporting 6000 counts properly already requires very high precision components.

HKJ

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Re: New EEVblog BM786 Multimeter
« Reply #82 on: October 28, 2020, 06:27:16 pm »
Simple: Because even 6000 counts is 0.016% accuracy. Supporting 6000 counts properly already requires very high precision components.

Usually not, it can be as bad as 0.16%

Fungus

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Re: New EEVblog BM786 Multimeter
« Reply #83 on: October 28, 2020, 07:25:56 pm »
Simple: Because even 6000 counts is 0.016% accuracy. Supporting 6000 counts properly already requires very high precision components.

Usually not, it can be as bad as 0.16%

Sure, it drops down to 600 counts if you're measuring (eg.) 7V, that's 0.16%.

The solution isn't to go to 500k counts though. 10k counts would be 0.01% on all ranges.

If we apply Benford's law the ideal number of counts is 20k.

https://en.wikipedia.org/wiki/Benford%27s_law

2N3055

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Re: New EEVblog BM786 Multimeter
« Reply #84 on: October 28, 2020, 08:15:42 pm »
Simple: Because even 6000 counts is 0.016% accuracy. Supporting 6000 counts properly already requires very high precision components.

Usually not, it can be as bad as 0.16%

Sure, it drops down to 600 counts if you're measuring (eg.) 7V, that's 0.16%.

The solution isn't to go to 500k counts though. 10k counts would be 0.01% on all ranges.

If we apply Benford's law the ideal number of counts is 20k.

https://en.wikipedia.org/wiki/Benford%27s_law

Benford's law is not so much relevant in electronics in this context. We have common voltages used: 5, 12, 13.2, 24, 48, 120, 240, 440 etc...
You measure according to system voltages, and those will have standardized, artificial grouping.

20000 is very good but 50000/60000 count is even better and keeps electronics measurements in long scale most of the time.

That is my observation.. Not a law.

joeqsmith

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Re: New EEVblog BM786 Multimeter
« Reply #85 on: October 29, 2020, 12:09:26 am »
If I only would have only taken a minute to read the title of that wiki page on Benford's law and became an expert, I could have saved myself $12K on the new 8.5 digit Keysight meter. How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg Software, documentation and test reports for the low cost NanoVNA & V2 Plus 4 may be found here: https://github.com/joeqsmith The following users thanked this post: uncle_sem, Marco1971 EEVblog • Administrator • Posts: 33275 • Country: Re: New EEVblog BM786 Multimeter « Reply #86 on: October 29, 2020, 02:40:57 am » For those interested in accuracy, the BM786 beats the BM869 on DC current, 0.075%+20 across three lowest ranges vs 0.1-0.15%. And better on the high end at 0.3% vs 0.5% Not bad considering the lower price point. The following users thanked this post: rsjsouza, Jacon, Marco1971, umbro, rernexy okurka • Contributor • Posts: 13 • Country: Re: New EEVblog BM786 Multimeter « Reply #87 on: October 30, 2020, 06:28:43 am » The BM786 model will be exclusive to the EEVblog. So Brymen won't sell the BM786 elsewhere with red housing, like they do with the BM235? Fungus • Super Contributor • Posts: 12595 • Country: Re: New EEVblog BM786 Multimeter « Reply #88 on: October 30, 2020, 06:58:09 am » So Brymen won't sell the BM786 elsewhere with red housing, like they do with the BM235? The BM235 existed before Dave ordered a blue one. EEVblog • Administrator • Posts: 33275 • Country: Re: New EEVblog BM786 Multimeter « Reply #89 on: October 30, 2020, 07:39:42 am » So Brymen won't sell the BM786 elsewhere with red housing, like they do with the BM235? The BM235 existed before Dave ordered a blue one. Technically, but I was the first to sell it, and I helped a little in the development and debug. I knew about it more than a year before it came out. I was also appointed the sole Australian distributor. EEVblog • Administrator • Posts: 33275 • Country: Re: New EEVblog BM786 Multimeter « Reply #90 on: October 30, 2020, 07:41:49 am » The BM786 model will be exclusive to the EEVblog. So Brymen won't sell the BM786 elsewhere with red housing, like they do with the BM235? Correct, it's a mid range model just for me, because the "official" Brymen Australian dealer already called dibs on the BM789, and Brymen are fiercely loyal to their dealerships, even if those dealership are hopeless. This is why I can't sell any other Brymen models. The following users thanked this post: okurka, rernexy Nixfried • Contributor • Posts: 13 • Country: Re: New EEVblog BM786 Multimeter « Reply #91 on: October 30, 2020, 07:48:54 am » If I only would have only taken a minute to read the title of that wiki page on Benford's law and became an expert, I could have saved myself$12K on the new 8.5 digit Keysight meter.

Awesome! 3458a robustness test incoming?

Fungus

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Re: New EEVblog BM786 Multimeter
« Reply #92 on: October 30, 2020, 08:38:39 am »
20000 is very good but 50000/60000 count is even better and keeps electronics measurements in long scale most of the time.

Why only "most of the time"? Shouldn't it be "all the time"?

Fungus

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Re: New EEVblog BM786 Multimeter
« Reply #93 on: October 30, 2020, 08:41:52 am »
If I only would have only taken a minute to read the title of that wiki page on Benford's law and became an expert, I could have saved myself $12K on the new 8.5 digit Keysight meter. Benford's law applies to any number of digits. All you need is a multimeter with a little oven in it. (How many digits before we have to control air pressure, too? Anybody know? I'm sure I read somewhere that some multimeters have a maximum altitude in their specification.) EEVblog • Administrator • Posts: 33275 • Country: Re: New EEVblog BM786 Multimeter « Reply #94 on: October 30, 2020, 09:04:20 am » 20000 is very good but 50000/60000 count is even better and keeps electronics measurements in long scale most of the time. Why only "most of the time"? Shouldn't it be "all the time"? Try measuring 7.0000V and see what happens. HKJ • Super Contributor • Posts: 2016 • Country: Re: New EEVblog BM786 Multimeter « Reply #95 on: October 30, 2020, 09:19:47 am » (How many digits before we have to control air pressure, too? Anybody know? I'm sure I read somewhere that some multimeters have a maximum altitude in their specification.) That is due to high voltage arching, more isolation distance is required at low pressure. Kleinstein • Super Contributor • Posts: 9588 • Country: Re: New EEVblog BM786 Multimeter « Reply #96 on: October 30, 2020, 10:50:56 am » Another problem at high altitude is that cooling gets less effective, both passive and with a fan. At least the fan could compensate with a little more speed. The main limit is the required (by the standards) distances going up at 2000 m altitude. So it's very common to find a break / limit at 2000 m, especially for higher voltage instruments. There is a small effect of pressure detectable for the metal can references (e.g. LTZ1000, LTFLU) - something in the sub ppm range. So only relevant of the very high end. This would not really limit the use at higher altitude - maybe a point to those who send a reference to NIST in colorado. There is always the problem of having voltage so you just have to switch to the next larger range. This can happen with 2000 counts and can happen with 6000 counts. There is nothing so special with the leading 1, it's more or less an even distribution on a log scale. It was a bit special in the old times (e.g nixi tubes) with the display part was expensive. The following users thanked this post: Marco1971 Fungus • Super Contributor • Posts: 12595 • Country: Re: New EEVblog BM786 Multimeter « Reply #97 on: October 30, 2020, 01:16:36 pm » The Fluke 87V manual says: The following users thanked this post: Marco1971 joeqsmith • Super Contributor • Posts: 8135 • Country: Re: New EEVblog BM786 Multimeter « Reply #98 on: October 30, 2020, 11:31:58 pm » If I only would have only taken a minute to read the title of that wiki page on Benford's law and became an expert, I could have saved myself$12K on the new 8.5 digit Keysight meter.

Awesome! 3458a robustness test incoming?

Once I learned I didn't need anything that fancy, I traded it in on a new Harbor Freight meter.
Software, documentation and test reports for the low cost NanoVNA & V2 Plus 4 may be found here:
https://github.com/joeqsmith

The following users thanked this post: AVGresponding

UnexpectedBill

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Re: New EEVblog BM786 Multimeter
« Reply #99 on: October 31, 2020, 06:22:54 pm »
I am curious if this meter will have any PC link/datalogging capabilities. Based on the manual and PCB pictures, I'm guessing that it will not.

Smf