Products > Test Equipment
New EEVblog BM786 Multimeter
Brumby:
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:
--- Quote from: radiolistener on October 23, 2020, 01:25:34 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?
--- End quote ---
Simple: Because even 6000 counts is 0.016% accuracy. Supporting 6000 counts properly already requires very high precision components.
HKJ:
--- Quote from: Fungus on October 28, 2020, 06:20:38 pm ---Simple: Because even 6000 counts is 0.016% accuracy. Supporting 6000 counts properly already requires very high precision components.
--- End quote ---
Usually not, it can be as bad as 0.16%
Fungus:
--- Quote from: HKJ on October 28, 2020, 06:27:16 pm ---
--- Quote from: Fungus on October 28, 2020, 06:20:38 pm ---Simple: Because even 6000 counts is 0.016% accuracy. Supporting 6000 counts properly already requires very high precision components.
--- End quote ---
Usually not, it can be as bad as 0.16%
--- End quote ---
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:
--- Quote from: Fungus on October 28, 2020, 07:25:56 pm ---
--- Quote from: HKJ on October 28, 2020, 06:27:16 pm ---
--- Quote from: Fungus on October 28, 2020, 06:20:38 pm ---Simple: Because even 6000 counts is 0.016% accuracy. Supporting 6000 counts properly already requires very high precision components.
--- End quote ---
Usually not, it can be as bad as 0.16%
--- End quote ---
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
--- End quote ---
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.
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