DEVELOPMENT OF A POLYETHYLENE DIELECTRIC CAPACITANCE MOISTURE SENSOR METER TO SUSTAIN FOOD QUALITY

Abstract

Some available moisture meters come with a look-up table when measuring crop moisture content. In order to eliminate time-wasting in measuring crop moisture, a moisture meter was developed from two coaxial aluminium rods with different diameters and a polyethylene dielectric, which were suspended between parallel plates in a sensor meter. Salt solutions were prepared to allow for the simulation of varying relative humidity conditions according to standard values at different temperatures (25, 30, 35, and 40°C). The sensor meters (AD7746 and SHT71) were characterized at experimental temperatures and relative humidity and the trend equations were programmed into a microcontroller for output on a digital display board. The output of the AD7746 sensor meter was verified by comparing the values of moisture content of rice and corn obtained with the SHT71 control moisture meter and oven drying method. After calibration, the output of SHT71, and AD7746 moisture meters were compared and it was observed that the highest deviation of temperature and relative humidity was 1.57°C and 0.98% at 30°C and 25°C, correspondingly and the lowest deviation of Temperature and relative humidity was 0.00°C and 0.45% at 25°C and 40°C, respectively. The oven-drying method verification showed that the moisture content disparity was 0.13% for corn (v1). Therefore, the moisture meter developed was found suitable for on-farm and warehouse moisture content measurements in storage systems.