Measurement And Control Of Concentration And Temperature Of AlCl₃Solution In The Beet’s Sugar Content Measurement

In the conventional method to measure the sugar content of beet, first we dig some from the beet using saw paste machine, then soak and agitate the sample for some time using PbCH3solution, next is to use polarimeter to measure the beet’s sugar content. After that, the remaining solution maintains Pb, which is a pollution to the environment. Instead of PbCH3solution, AICl3solution has less pollution to the environment. Thus, AICl3solution is an ideal replacement of PbCH3solution.This topic starts with the measurement of electroconductivity of solution in a solution tank. According to the relationship between electrocnductivity and concentration, I redirectly measure the concentration of the solution. Because conductivity changes with the temperature, I keep the temperature of the solution stable.Apart from this, I also conduct measuring warning and interlock for the solution level. The main works i do are as follows:(1) aimed at the demand of the topic, analyse the whole frame and measurement principle, and draw circuit schematic with Protel software, and made printed circuit board.(2) with respect to hardware, AT89S52micro controller is used as the main processor, it receives and deals with the signal of concentration sensor and temperature sensor collects, and display the result through the display circuit. AD650is used to convert analog signal to digital signal. Optocouplers6N137and TIL113are used to isolate signals.I design analog signal amplifying circuit and solution level high or low warning circuit. The temperature is controlled through solid state relay and power control strategy.(3) with respect to software, I realize the function of temperature measurement, temperature control; concentration measurement, concentration control; solution level measurement and warning; solution level low and stop warming interlock; concentration and temperature display and setting, etc, and also debug the software.(4) I did a series of experiments, and get a lot of experiment data and analyse them. The conclusion is that the measurement system is quite stable against interference and the measurement result is quite accurate.On the base of measuring temperature, write the program of controlling temperature and bring forward a kind of algorithm. The experiment proved that the temperature can be controlled in the rang of0.5℃higher or lower than setting temperature.