Moisture testing Analytics

I am looking into getting a precision scale so that I can do green coffee bean moisture content analysis. Determining moisture content is a simple process. Samples of green beans are collected. Each sample set is weighed. The sample are then ‘cooked’ for 8 minutes at 160^o F and the result weighed. The weight lost is the water. There are traces of volatiles lost also but water is the main content lost. For heating I am planning on using an infrared oven I have.

In looking at scales, accuracy is a key factor in cost. As a scale handles more weight, it is harder to get accuracy. As an example I am looking at the My Weight iBalance 601. This scale has a 600 gram capacity, can be connected to the computer via RS232 but only has a .01 gram accuracy. The iBalance 211 is twice as expensive, has only a a 210 gram capacity but is accurate to .001g.

The i601 is attractive as it could do both moisture measurement but also could do before and after roast weighing to record % loss due to the roast. My HotTop has a capacity of 250g. The key question is what is the accuracy of moisture content I could calculate with a scale of .01g accuracy.

In this table I assume 10 grams of green beans in and 8.9 grams out for an 11% moisture content. Then I vary the 10 and 8.9 values by the stated accuracy of the scales and calculate the moisture. The swing values are 10+ accuracy with 8.9- accuracy and the reverse 10- accuracy with 8.9+ accuracy. With .01g accuracy the moisture reading could vary by .4% while .005g accuracy reduces that to .2% accuracy.

From what I can see the lower end moisture meters use .01g accuracy.

10 grams in	8.9 grams out	11% moisture content
Weight in	Weight out	Percent	Swing	Swing rounded
0.01	Accuracy
9.99	8.91	10.8108%		10.8%
10.00	8.90	11.0000%		11.0%
10.01	8.89	11.1888%	0.3780%	11.2%
0.005	Accuracy
9.995	8.905	10.9055%		10.9%
10.00	8.90	11.0000%		11.0%
10.005	8.895	11.0945%	0.1890%	11.1%
0.002	Accuracy
9.998	8.902	10.9622%		11.0%
10.00	8.90	11.0000%		11.0%
10.002	8.898	11.0378%	0.0756%	11.0%
0.001	Accuracy
9.999	8.901	10.9811%		11.0%
10.00	8.90	11.0000%		11.0%
10.001	8.899	11.0189%	0.0378%	11.0%
0.0001	Accuracy
9.9999	8.9001	10.9981%		11.0%
10.0000	8.9000	11.0000%		11.0%
10.0001	8.8999	11.0019%	0.0038%	11.0%