| Temperature and humidity measurements are widely used, the standard temperature and humidity measuring instrument is mainly used in metrology, meteorology, military and other fields to achieve accurate measurement of high-precision temperature and humidity, which can also be used as a reference standard for calibration of other Temperature and humidity instrument.Digital Ventilation Psychrometer is a kind of important humidity standard instruments, accuracy of temperature measurement is an important factor constraining accuracy of humidity measurement,Digital Standard Temperature and Humidity measuring Instrument designed in the paper, emphasis on improving the accuracy of temperature measurement to achieve the purpose of high-precision humidity measurement.The design of the instrument is based on Wet and Dry ball theory, putting Single-chip Microcomputer as the control core, adopting Thermistor (LPTC) Balanced Bridge to collect temperature,using the valve of temperature and atmospheric pressure to calculate the relative humidity. The hardware system consists of temperature and pressure sensor input circuit, CPU and expansion circuit, ICL7135 analog-digital conversion circuit, the keyboard circuit, liquid crystal display circuit, power circuit, as well as other expansion circuit. Software include:Data collection procedure, the calculation procedure. Parameter storage and calibration procedures, Display program and keyboard driver procedure.The Temperature and Humidity Measuring Instrument can collect 15 channels of temperature signal in real-time,which is used to calculate the value of 7 channels relative humidity;when data acquisition and processing,it shows the time with real-time clock functions, and the clock has a adjustment function; it can collect real-time value of atmospheric pressure from the atmospheric pressure sensor. The system's temperature and humidity measurement is on the basis of Thermodynamics theory of Wet and dry ball, temperature, humidity, air pressure is displayed in digital form.and the value of temperature and air pressure can be easily amended.guarantees the system performances of high-stability and high-precision. |
