DEVELOPMENT OF PENETROMETER TO MEASURE SOIL STRENGTH

Abstract

Penetrometer is a device used to measure the strength of soil .The cone penetrometer is widely used in tillage and off road mobility researches. However, the instrument used for measuring this important parameter is not readily available in Nigeria. Following the recommendation by America Standard for Agricultural Engineering (ASAE), a fundamental digital static cone penetrometer has been developed and calibrated. The penetrometer consist of mechanical unit and the electronic measuring unit. The mechanical part consist of: s-type load cell to measure force exerted on the soil. steel rod and cone probe. The electronic measuring unit comprises of; differential amplifier. buffer amplifier, microcontroller, ultrasonic sensor to measure depth of penetration, secure digital shield to log data and display unit. The penetrometer was calibrated by applying known mass from the laboratory on the s-type load cell to get the output voltage on a digital multimeter. A performance test was carried out to compare the reading obtained from the developed penetrometer and the proctor penetrometer, the mean reading for cone index from the test carried out shows that the developed penetrometer has a cone index of 1.514Kpa compared to that of the proctor cone penetrometer which has 1.640Kpa. The correlation coefficient of the two penetrometer is 0.883. The penetrometer developed has demonstrated the possibility of local design and manufacture of hand held static cone penetrometer which can give comparable and appreciable precision has imported one. This research work will help agriculturist and soil scientist in the study of soil properties to increased crop yield.