Design Of Temperature,humidity And Pressure Measuring Instrument

As important physical parameters, temperature and humidity are widely used in meteorology monitoring, food storage, industrial and agricultural production , military and industrial control fields. It's of great social and economic meaning to build a reliable high precision temperature and humidity measurement system.The chief task of the subject is to build a high precision temperature, humidity and pressure measuring system. On the of basis analysis on the development status of measuring technique, we designed a system base on Principles of dry and wet bulb combined with microcontroller technologies, and accomplished the related hardware and software design.The measurement of temperature and humidity of this system is based on the principles of dry and wet bulb. Putting Single-chip Microcomputer AT89C52 whick with External Interface ciucuit of GAL16V8 logic control,E2PROM 28C04 and real time clock DS12887 as the control core,adopting LPTC thermistor and Balanced Bridge to measure 15-channel temperature values, and then using equation of dry and wet bulb to calculate the relative 7-channel humidity values, adopting ICSensors Co.'s 17 piezoresistance pressure transducer to measure atmospheric pressure, and in coordination with MPX (CD4051,CD4052), A/D converter ICL7135,High Precision operational amplifier OP07, the system can achieve high precision measurement of temperature, humidity and pressure. Equipped with 4×6 matrix keyboard, OLED display terminal, serial communication etc., the instrument can provide friendly MMI. Modularization software includes: main procedure, data collection procedure, the calculation procedure, parameter storage and calibration procedures, display program and keyboard driver etc.Practical test shows the system's perfect reliability and maintainability. With the temperature measuring precision of±0.01℃and the relative humidity measuring accuracy better than 1%RH,as well as its flexible uses , the instrument is of great social and economic value and have a bright application prospect.