INTEGRATED TEMPERATURE AND RELATIVE HUMIDITY SENSORS: IN WIRELESS ENVIRONMENTAL CONTROL AND MONITORING APPLICATIONS

摘要

Environmental sensors are used in many areas, including weather forecasting, air quality monitoring, ecological research, agriculture, wildlife monitoring and so on. Some of the sensor types used in environmental monitoring and control are temperature, humidity, pH, acoustic, solar radiation, light level, wind speed and direction, atmospheric pressure, rain, and chemical compounds in air and water (see Table 1 of the most common sensors). The output signal of some sensors is digital, with the data usually sent in serial format either in standard RS232, SPI or I2C bus protocols. Some sensors provide analog output voltage, so an A/D converter must be used to convert the signal into digital format before it's processed. Others, however, provide more than one type of output, as is the case with the integrated sensors SHT11 and RHT03 listed in Table 1. In environmental data collection applications, a network of mobile sensor stations is usually established with each station sending its own data at pre-assigned times to a central processing unit. The mobile sensor stations are identified by unique identity codes, or by using GPS to send their geographical co-ordinates and other data.