Campbell DMM600 Manuel d'instructions télécharger pdf (Page 11)

DMM600 Duff Moisture Meter

sieve is included with the DMM600 for this purpose. Forcing the sample

material through the sieve will improve measurement accuracy and

repeatability.

The heterogeneity of material size can be characterized by making repeated

measurements of the same material. Place the duff in the sample chamber and

make a measurement. Remove the duff from the chamber, restore its natural

structure by working it by hand then put the duff back in the sample chamber

and make another measurement. Repeat this several times. If the

measurements vary by more than about 5% water content, this indicates that

the material should be sieved before measuring to reduce the effect of the

fragment size variation.

4.3 The Water Content Measurement Method

1. Unscrew compression knob completely then loosen (don’t remove) the

captive screw and remove sample chamber cap by turning slightly

counter-clockwise and lifting.

2. Place duff in the sieve then place the sieve atop the sample chamber.

3. Finger-work the duff in the sieve until it moves through the sieve and into

the sample chamber. The sieve may need to be filled more than once to

fill the chamber. The sample should fill the sample chamber to about the

beginning of the bevel on the top edge. Don’t overfill the chamber or the

compression piston may bind.

4. Remove the sieve, ensure that the compression knob is fully out and

replace the sample chamber cap by aligning the slots of the cap with the

pins of the sample chamber. Turn cap slightly clockwise and tighten the

captive screw.

5. Turn on the DMM600 then turn the compression knob clockwise until the

double-beep audible signal indicates the measurement has been made, the

volumetric water content value is read from the display.

6. Read water content from display. If user calibrations are loaded, the

display will toggle between factory and user values. Water content is only

displayed while sample is compressed.

7. Turn knob counter-clockwise to stop. A single beep indicates the sample

is no longer compressed and the measured water content value is no longer

displayed. Loosen the captive screw, remove the sample chamber cap and

remove the sample from the sample chamber. If residual water is apparent

on the sample chamber surfaces, wipe dry.

4.4 DMM600 Standard Calibration

Figure 3 shows the response of the DMM600 as described using the standard

calibration that was derived by Campbell Scientific using duff from lodgepole

pine, spruce, Douglas fir, larch and oak vegetation types. The error bars

indicate that the measurement accuracy decreases as water content increases.

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Campbell DMM600 Manuel d'instructions Page 11