Design Of Liquid Level Real-time Measurement System Based On CIS

At present,the liquid level measurements are carried out by using manual reading method in many occasions.This method is time-consuming and inefficient and lead to large errors.Moreover,it is not suitable for harsh applications such as high temperature and high pressure.With the development of science and technology,the requirement of liquid level measurement is getting higher.It is of great engineering value to study a highprecision intelligent liquid level measurement system.The linear array CIS(Contact image sensor)is used to obtain the feature height information of liquid of different media contained in transparent vessels.The homogeneous light will go through the transparent vessel and image information of liquid level will be received by CIS on the other side.The intensity of the transmitted light received by CIS at the concave surface is different from that received at liquid and air segments.The pixel points of the concave surface can be obtained by applying one dimensional image edge extraction algorithm,which can reflect the change of the liquid level real-timely.With the core of STM32F407 microcontroller the design and implementation of the hardware circuit are accomplished,including peripheral working circuit,CIS signal acquisition circuit,SD card storage circuit,OLED display circuit,buttons and RS232 communication circuit,etc.Furthermore,the software design of the corresponding function is completed.The designed modules include CIS driving signal,one dimensional image edge extraction algorithm,real-time display of liquid level measurement value,Fat Fs file system transplantation based on SD card,real-time clock and overrun alarm setting function,the upper computer software of RS232 communication Finally,the experimental platform is established and the experimental verification of the developed system is carried out.The experimental results indicate that the system can measure the level change of transparent,translucent and opaque liquid in real time.It is able to meet the requirement of real-time high-precision measurement of liquid level.