Campbell DMM600 Manuál s instrukcemi stáhnout pdf (Strana 10)

DMM600 Duff Moisture Meter

FIGURE 2. Downloading coefficients to convert to gravimetric water

content for above example.

4.1.1 Determining Duff Sample Bulk Density

The bulk density of the sample at time of measurement is determined as

follows.

1. After the measurement is made, count the number of compression knob

rotations required to move compression piston from measurement position

to completely out.

2. Use following equation to calculate volume of sample at time of

measurement.

Volu me rota tio n s=−157 97 7 25..*

3. Dry then weigh the sample used for the measurement.

4. The bulk density in g/cm

is the dry weight divided by the volume.

4.2 Duff Size and Water Content Heterogeneity

There is considerable variability in both the physical characteristic and water

content distribution in duff. Because this variability can be significant over a

small area or even within a handful-sized sample, several measurements of the

material are needed to obtain reliable estimates of the water content for the

area of interest.

Duff commonly varies in fragment size, and it may be necessary to grind or

chop the material to improve measurement accuracy and repeatability. A #4

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Campbell DMM600 Manuál s instrukcemi Strana 10