Design On An Integrated System Of Temperature And Humidity Sensor

Humidity measurement plays an important role in some research and application fields.Humidity sensors are widely used in weather station,home appliances,medicine,automatic control and other fields.Exposed to the external environment,humidity sensors are easily affected by temperature and pollutants.As a result,the reliability and accuracy of the sensors were reduced.This paper presents a temperature and humidity sensor integrated system.The system includes a temperature sensor,a humidity sensor,a MCU chip and related communication interface.The humidity sensors was calibrated,Corresponding package and software algorithm of the system were designed as well.The specific work of this paper are as follows:(1)Hardware circuit of the system was designed and constructed.A Platinum-resistive temperature sensor and a capacitive humidity sensor were used to measure the environmental temperature and humidity.An IC chip(PCap02)was used to process the measured data.A communication circuit including an MCU,an LCD and a power module was developed to communicate with the integrated system and the user.(2)Software of the system was designed.Based on the analysis of temperature drift principle of capacitive humidity sensors,the temperature compensation formula of capacitive humidity sensors was derived in this paper.The humidity output of the sensor was calibrated by software.The accuracy of humidity sensors were effectively improved.In order to realize the communication between PCap02 and LCD,communication software was designed.(3)Package structure of the system was designed.A temperature sensor,a humidity sensor and a PCap02 chip were integrated on a PCB.A package shell was designed to protect the integrated system.Some ventilation windows were designed in package shell to ensure the air exchange between integrated system and external environment.(4)Performance of the system was tested.In order to obtain the parameters of the temperature sensor and the humidity sensor,a test system was designed.The integrated system was tested and analyzed as well.Compared with the traditional humidity sensors,the accuracy and stability of the integrated system were improved.The test result showed that:the deviation of the temperature sensor is 0.56 ?,the linearity is 0.067%.The hysteresis of the humidity sensor is-5.71%RH,the response time is 5s and the deviation is 2.756%RH.