Development Of Solution Freezing Point Measurement Instrument Based On ARM

The freezing temperature of liquids, namely the balance temperature between their liquid and solid state, is called freezing point. The freezing point of a solution changes with its concentration. Usually, the higher the concentration is, the lower the freezing point becomes. The solution freezing point measurement instrument is important to medicine research, production and application. At present, the instument commonly used to measure liquid freezing point are mainly operated by hands, and can only detect one sample at time.The developed solution freezing point measurement is based on Raoult's law, which describes the relationship between drop value of freezing point of a solution and its molar concentration. The instrument is characterized by automatic operation, high precision, high efficiency and intelligence. The innovative points of the instruments include the use of ARM(LPC2214) as the CPU, multiple sample measurement capability, implementation of bar code scanning module for easy filing of samples. The ARM is responsible for measurement control, sample transformation, data acquirization, data analysis, disply and printout.The main work of the thesis includes the following five aspects:1. Study of the principle of solution freezing point measurement instrument.2. Design of CPU module circuit, motor driving circuit and real-time temperature monitoring circuit. Selection of electronics chips and components.3. Software design of the ARM system, control of keyboard miniature printer and liquid crystal screen.4. Electronic circuit debugging, including thermal sensor calibration, signal amplification circuit, motor driving circuit, and circuit parameters setting.5. Software debugging; calibration of the instrument by comparing purify-water with liquor. Reproducibility test and error analysis of the instrument.