User manual

17.03.2006, BR Moisture Conversions Seite 1
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Units of moisture measurings and their conversions
Established moisture measuring instruments (like GMH3830 before V1.4) are displaying the material moisture relative
to the dry weight of a material. In practice other units are used, too, especially the wet basis moisture content. The
display of newer instruments (like GMH3830 V1.4 or GMR100) can be switched to both units.
Moisture content MC or u (relative to dry weight) = dry basis moisture content
Most common unit for moisture measuring instruments. The unit is %, sometimes used: % MC.
The unit expresses the moisture content like calculated below:
Moisture content u [%] = (weight
wet
- weight
dry
) / weight
dry
*100
Or:
Moisture content u [%] = (weight
water
) / (weight
dry
) *100
weight
wet
: weight of the wet material
weight
water
: weight of water in the wet material
weight
dry
: oven-dry weight of material
Examples: 1kg of wet wood, which contains 500g of water has a moisture content u of 100%
1kg of wet wood, which contains 200g of water has a moisture content u of 25%
Wet-Basis Moisture Content w (relative to total weight)
The wet-basis moisture content expresses the ratio of the mass of water to the total mass of the substance. The ratio
is represented by the following equation (the unit is % as well):
wet-basis moisture w[%] = (weight
wet
- weight
dry
) / weight
wet
*100
Or:
wet-basis moisture w[%] = (weight
water
) / weight
wet
*100
Conversion meter display u -> wet-basis moisture w
wet-basis moisture w[%] = 100 * Moisture content u[%] / (100 + Moisture content u[%])
Examples: 1kg of wet wood, which contains 500g of water has a moisture content u of 50%
1kg of wet wood, which contains 200g of water has a moisture content u of 20%
Conversion moisture content u - wet-basis moisture content w
0
10
20
30
40
50
60
0 102030405060708090100110120130140150
moisture content u [%] = display of GMH38x0
wet-basis moisture content w [%]