A Microprocessor Automated Rillmeter

ABSTRACT THE measurement of erosion and rill development during natural or artificial rainfall requires a rill-meter that can be installed, make the measurements, and be removed from the plots quickly. The design cri-teria were that the device: (a) measure 300 or more sur-face elevations in less than 1 min., (b) have a vertical resolution of 1 mm over a 25 cm range, (c) be battery operated for remote field operation, (d) be light weight and compact enough for easy handling by two people, (e) be rugged enough for extensive field use, and (f) auto-matically record the data on an easily accessible medium. The rillmeter designed, constructed, and tested measures 312 surface elevations with sensing rods ar-ranged in three rows of 104 rods each. The rods are spac-ed 1 cm apart within the row and 5 cm apart between the rows. The rillmeter is attached to a frame that can be mounted quickly on field elevation stakes. A 12-V DC electric motor and a positive mechanical drive lowers a movable platform containing a grid of sensing rods that open individual electrical contacts upon touching the soil surface. A microprocessor scans all of the contacts several times before the platform moves 1 mm and stores the platform position at which each sensing rod touches the soil surface in an associated memory location. After all the data are in memory, the microprocessor stores them on magnetic cassette tape. Field and laboratory tests showed that the rillmeter does meet the design requirements.