Products > Test Equipment
New EEVblog BM786 Multimeter
drussell:
Speaking of cool feature hacks....
I almost pulled the trigger and ordered one of these when Dave first released them as it looks like it would make a great "daily driver" replacement for my well-worn, aging Amrel (American Reliance) model 37 I've been using for the past 30 years... ??? The good ol' 37 has served me well over the years (it is basically a functional clone of a Fluke 87, which was way out of my price range back in those days, sold for less than half the price, even has a yellow holster 8) ) but it is getting temperamental as a daily-use meter being carted around, left in vehicles in temperature extremes, etc. I have to clean the zebra strip for the LCD and the button pads etc. every few months to keep it properly operational. It's simply just wearing out from 30 years of constant use.
After watching Joe's video series, it looks pretty much perfect for me except for one aspect of one feature that I do use on a fairly regular basis, and that is being able to measure audio-frequency AC voltages to within a few percent, right up to at least 20 kHz. Joe's testing indicates that the -3 dB point is way down at 7-8 kHz, which would be really annoying to have to attempt correct for or carry another meter all the time for making AF measurements.
Joe, since you've at least taken a cursory glance at the circuitry, is it likely that I could modify one to extend the frequency range slightly? Do you suppose that the limit is coming from something in hardware, like where I could possibly just change a couple capacitors in a filter or something and get it up to at least 20-25 kHz for the -3 dB point, (ideally it would be nicer to have the -3 dB point up at 40-50 kHz but I could live with 20,) or is it something integrated into the chipset that is causing the limitation? Like, how is it doing the RMS, is it being calclated in the main chip? Not being able to field-update the firmware makes that a show-stopper if it's in the chip I suppose.
I have a tube of decent quality RMS converters somewhere (Analog Devices, I think) that I could make an adapter box or something with better response, but then guaranteed I won't have it with me when I need it, and it is not really practical to try to replace the whole AC front end unless it is already using a separate converter chip and that's where the limitation lies, which I highly doubt....
Anyway, any thoughts on whether I might be able to extend the AC frequency response about an octave and a half?
... that would turn it into pretty much the ideal meter for me!
HKJ:
--- Quote from: drussell on January 22, 2021, 01:31:34 pm ---Anyway, any thoughts on whether I might be able to extend the AC frequency response about an octave and a half?
--- End quote ---
You could move to the next model in the line: BM789
EEVblog:
--- Quote from: drussell on January 22, 2021, 01:31:34 pm ---After watching Joe's video series, it looks pretty much perfect for me except for one aspect of one feature that I do use on a fairly regular basis, and that is being able to measure audio-frequency AC voltages to within a few percent, right up to at least 20 kHz. Joe's testing indicates that the -3 dB point is way down at 7-8 kHz, which would be really annoying to have to attempt correct for or carry another meter all the time for making AF measurements.
--- End quote ---
The BM789 does that.
I don't have a BM789 to compare, but it's the same PCB.
Fungus:
--- Quote from: drussell on January 22, 2021, 01:31:34 pm ---After watching Joe's video series, it looks pretty much perfect for me except for one aspect of one feature that I do use on a fairly regular basis, and that is being able to measure audio-frequency AC voltages to within a few percent, right up to at least 20 kHz. Joe's testing indicates that the -3 dB point is way down at 7-8 kHz, which would be really annoying to have to attempt correct for or carry another meter all the time for making AF measurements.
Anyway, any thoughts on whether I might be able to extend the AC frequency response about an octave and a half?
... that would turn it into pretty much the ideal meter for me!
--- End quote ---
Brymen makes plenty of meters simliar to this one. A lot of them go up to 100kHz.
drussell:
--- Quote from: HKJ on January 22, 2021, 01:47:15 pm ---
--- Quote from: drussell on January 22, 2021, 01:31:34 pm ---Anyway, any thoughts on whether I might be able to extend the AC frequency response about an octave and a half?
--- End quote ---
You could move to the next model in the line: BM789
--- End quote ---
Well, obviously... but then I wouldn't be buying the EEVblog version from Dave. :)
The BM789 also doesn't appear to be very widely available yet and most places also appear to want way more money than Dave is charging for his BM786.
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