Campbell Scientific DOT600 Roadbed Water Content Meter - Manual (Page 22)

Appendix A. Design and Calibration
A.2 Description of the Modified Device
The method of water content measurement used by the DMM600 is also used
in the DOT600 but with several significant differences listed here.
• The electronics for the dielectric measurement method are modernized to
provide improved measurement accuracy and resolution. Surface-mount
components are used to obtain higher speed measurements which directly
improves water content measurement accuracy.
• An integral scale is used to measure sample weight.
• The compression mechanism allows maximum compression of about 45
psi compared to less than 3 psi with the DMM600
• Magnetic displacement sensors are used to accurately measure sample
volume and applied force. With measured sample volume and weight, dry
bulk density can be calculated which allows water content to be expressed
in gravimetric terms.
• A CR850 datalogger with 8-line, 21 character display and control keypad
is the user interface and performs calculations along with controlling
measurement sequence and generating a record of all measurements and
parameters entered by the user.
• All DOT600 components are housed in a rugged, plastic carrying case.
A.3 Detailed Description of any Field and Laboratory
Work
Field work
The DOT600 has been used in the field to evaluate general operation, and for
demonstration. All of the calibration work was done in the laboratory.
Description of laboratory calibration
Laboratory calibration is required for the following components of the
DOT600 system:
1. scale
2. compression piston and spring-base travel
3. water content measurement
A-2