FABRICATION OF A DIGITAL STATIC CONE PENETROMETER WITH USB OUTPUT

Abstract

Humans have been probing ground since they could hold sticks, but only in recent times have their probes been scientific. Researchers interested in studying soil stratification probed the ground with pointed rods during early 1900s. A more refined instrument called a cone penetrometer was invented in Netherlands during the mid-1930s to measure soil strength. Cone penetrometers measure soil penetration resistance or soil strength encountered at various depths as the cone shaped object is pushed steadily into the ground. Until recently, penetrometers were comprised of a dial indicator with a stress ring connected to a round rod with scaled depth markings. The rod has a cone-shaped tip at one end and a handle for pushing the cone into the ground on the other end. Using these penetrometers was a cumbersome operation best completed by two people; one to push the penetrometer into the ground and read the force on the dial indicator, and the other to record probe depth and force. In this thesis, a Digital static cone penetrometer has been designed which can record the output with fixed time intervals automatically. The result will be shown in a table format comprising serial number, load and displacement. For the load output, a load cell has been used. In this, four strain gauges are used in a Wheatstone bridge configuration. For displacement, Linear Potentiometer has been used which measures the total distance between the initial ground level and the final position of the rod. The result is then transferred to output device using a sensor. Finally all the data is simultaneously gathered for a fixed time interval providing the final table comprising serial number, load and displacement. This data is then recorded and saved in the output device i.e. pen drive.