DESIGN AND ELECTRICAL CHARACTERIZATION OF A HUMIDITY SENSOR

This project objectives are to propose a method to fabricate a humidity sensor based
on the changes in the Relative Humidity (RH %). A part for this project is to design
and construct the humidity sensor circuit which is necessary to support the humidity
sensor. Overall of this project can be classified as to design a working humidity
detector prototype which consists of a humidity sensor and the electronic circuit.
Zinc Oxide (ZnO) is identified as one of the best materials that can be used to
fabricate the sensor. Zinc Oxide is called a hygroscopic material because of its
tendency to absorb moisture. The capacitive type of sensor is chosen as a method to
fabricate the sensor because it is the most sensitive to the presence of humidity. The
Zinc Oxide is first mixed with diamine and Epoxy (hardener and adhesive) to become
a pellet. This pellet becomes the dielectric for whose capacitance is measured to
detect the humidity level and convert into the electrical signal.
Laboratory experiments have been conducted to test the sensor performance. The
signal conditioning circuit is constructed to complete the test. The Relative Humidity
(RH %) is varied in ranges of 10% RH starting from 20% RH until 90% RH. From
the experimental observation, the output voltage is found to correspond to the
changes in the relative humidity. The output voltage increased when the relative
humidity is increased and output voltage decreased when the relative humidity is
decreased. The experiment also is conducted to test the standard humidity sensor and
the result from the real sensor is become a standard reference for fabricated sensor.