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Brymen BM789

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chebo:
Hi owners!
Who could repeat my simple experiment to check the accuracy of the Crest mode?

I manually closed and opened the switch shown in the diagram, simulating a voltage drop. The average value for several measurements in the Crest mode was 7.60 V. As a result, the relative error was approximately 4%.

Is this a normal error? What will happen to you?

joeqsmith:

--- Quote from: chebo on December 03, 2024, 07:58:39 am ---Hi owners!
Who could repeat my simple experiment to check the accuracy of the Crest mode?
(Attachment Link)
I manually closed and opened the switch shown in the diagram, simulating a voltage drop. The average value for several measurements in the Crest mode was 7.60 V. As a result, the relative error was approximately 4%.
(Attachment Link) (Attachment Link) (Attachment Link)
Is this a normal error? What will happen to you?

--- End quote ---

I saw your double post about the car battery.  Personally, I would use a scope for that application. 

For the BM789,  assuming we meet the 35ms minimum,  in this range I would expect it to fall within +/-1V.  Yours appears much tighter than that.   

CREST mode (Instantaneous Peak Hold)
Accuracy: Specified accuracy +/- 100 digits for changes > 0.35ms in duration
Availability: Voltage and Current functions
Resolution: 6000 counts

For the BM869s:
Crest mode (Instantaneous Peak Hold)
Resolution: 5000 counts
Accuracy: Specified accuracy +/- 100 digits
for changes > 0.8ms in duration

For the Fluke 189:
Specified accuracy ±100 counts up to 5,000 count (full
range) reading. For higher peak readings (to 20,000
counts), specified accuracy ± 2% of reading.
250 μs for repetitive peaks; 2.5 ms for single events. Use DC function settings below 20 Hz. 50 mV range not specified.

chebo:

--- Quote from: joeqsmith on December 03, 2024, 01:30:38 pm ---For the BM789,  assuming we meet the 35ms minimum,  in this range I would expect it to fall within +/-1V.

--- End quote ---
Yes, it seems so. And that's what Brymen's engineer answered me too: "07.60V" reading falls in "+- 100 digits" tolerance.
It was not very clear to me what these +-100 digits meant. But now everything has become clear. If you add this systematic error to the readings, the result coincides with what the oscilloscope showed.

coromonadalix:
brymen 785  would be like some fluke 83 85 87 series ... no dual displays, but  vs the dual display ones, the price gap is not huge ... ?

old Gossens  have the auto mode i sometimes use,  switch between ohms volts  ...  practical  loll

joeqsmith:

--- Quote from: chebo on December 03, 2024, 01:48:42 pm ---
--- Quote from: joeqsmith on December 03, 2024, 01:30:38 pm ---For the BM789,  assuming we meet the 35ms minimum,  in this range I would expect it to fall within +/-1V.

--- End quote ---
Yes, it seems so. And that's what Brymen's engineer answered me too: "07.60V" reading falls in "+- 100 digits" tolerance.
It was not very clear to me what these +-100 digits meant. But now everything has become clear. If you add this systematic error to the readings, the result coincides with what the oscilloscope showed.

--- End quote ---

I had a quick look at the manuals for some of the other higher end meters I have on-hand but don't believe any of them are spec'ed much better. 

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