Campbell DMM600 Instrukcja Obsługi Pobierz pdf (Strona 15)

DMM600 Duff Moisture Meter

samples to obtain samples with a range of water contents, and the measurement

process repeated on the wetted samples.

6.3.2 Detailed Calibration Procedure

Spreadsheet file DMM600 calibration spreadsheet.xls is provided with the

DMM600 to assist with calibration calculations.

1. Collect a sample of the material to be used in the calibration that is four to

five times the volume of the sample chamber. Sample chamber volume is

approximately 140 cm

. Place the material in a plastic bag that can be

sealed to prevent drying and let the sample set for 8 to 12 hours. This

sitting time will allow the water content to equilibrate throughout the

sample.

2. Load a portion of the sample into the chamber and take a measurement.

See section 4.2. for discussion of sample heterogeneity. Record the

frequency in MHz that is displayed as “Raw”.

3. Unscrew the compression knob counting the number of turns from the

position of measurement to fully out. Use the index on the compression

knob and the radial lines on the sample chamber cap for this. Record the

number of turns.

4. Remove the material from the sample chamber to a container of known

weight. Weigh the sample and container. Repeat steps 2 and 3 at least

three times using different portions of the sample.

5. Dry the samples and then weigh. See section 8 for guidance on drying

samples.

6. Using the dried samples repeat steps 2 through 4. The dried sample

measurements are zero water content values.

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

measurement.

Volume rotations=−157 97 7 25..*

8. Calculate the bulk density (g/cm

) by dividing the dry weight of the

sample by the volume.

9. Estimate the amount of water to add to the dry samples to obtain 50%

volumetric water content using the following equation.

wet sampleweight dry sampleweight

bulk density













100

The value 50 is the target volumetric water content.

10. Place the sample(s) in sealable plastic bag(s) and add water. Work water

into sample. Set aside for 8 hours to allow equilibration.

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