Volumetric whole bean coffee dosing, a quick consistency test
- Bluecold
- Posts: 1774
- Joined: 16 years ago
As the Versalab uses a volumetric bean-dosing system, and I had a doser laying around gathering dust, I figured I could repurpose my doser to dispense precise amounts of whole beans. This would save me some mucking about with a scale as my grinder is basically retention free.
So I threw some beans in my doser, and measured the consistency of the output when thwacking the doser.
I used one-thwack and double-thwacking and set the doser at two heights, very low and as high as it could go. I did twenty doses with each experiment run. Each time I dropped the dosed beans back in the doser for a consistent doser height. The doser was half-full and completely covered the dosing star. The first three samples where not counted with the experiment to ensure consistent filling.
The results are as follows:
The results are a bit puzzling as one would expect the double-thwack experiments to have less standard deviation and variance as you use two samples. Apparently, there is a bit of correlation between the samples. And I expected a higher bean column to dose more consistently as the relative impact of a few beans being scraped away from the top would be lower. In any case, I think this is a solid indication that volumetric bean dosing is not sufficient for the discerning home user. Or that a doser designed for ground coffee is not suitable for whole beans. What the parameters for consistent volumetric whole-bean dosing would be I don't know.
--edited to clarify the reason for the test---
For those wondering about the consistency of a doser for ground coffee, Jim Schulman stated this to be within 1/3 gram of the desired dose
How I Avoid Single Dosing
So I threw some beans in my doser, and measured the consistency of the output when thwacking the doser.
I used one-thwack and double-thwacking and set the doser at two heights, very low and as high as it could go. I did twenty doses with each experiment run. Each time I dropped the dosed beans back in the doser for a consistent doser height. The doser was half-full and completely covered the dosing star. The first three samples where not counted with the experiment to ensure consistent filling.
The results are as follows:
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low height | higher height
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1 thwack 2 thwack | 1 thwack 2 thwack
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Mean (gr) 5.01 9.78 | 9.04 18.56
Max (gr) 5.3 10.7 | 9.4 19.5
Min (gr) 4.5 9.3 | 8.7 17.8
StDev(gr) 0.22 0.35 | 0.25 0.50
Variance 0.05 0.13 | 0.06 0.25
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--edited to clarify the reason for the test---
For those wondering about the consistency of a doser for ground coffee, Jim Schulman stated this to be within 1/3 gram of the desired dose
How I Avoid Single Dosing
LMWDP #232
"Though I Fly Through the Valley of Death I Shall Fear No Evil For I am at 80,000 Feet and Climbing."
"Though I Fly Through the Valley of Death I Shall Fear No Evil For I am at 80,000 Feet and Climbing."