Research On The Liquid Particle Counting System Based On Photoresist Method

A large number of studies have shown that 70% of hydraulic system failures are caused by the pollution of hydraulic and lubricating oil,and the failures caused by solid particle pollution account for 60% to 70% of the total pollution failures.Existing particle measurement equipment has high cost and heavy weight.,and it is of great significance to develop a portable,low-cost particle measurement equipment.The main research contents of the thesis are as follows:Chapter 1: Introduction.Current typical oil particle measurement methods is introduced.Pros and cons of various methods is compared.The domestic and foreign research status of photoresistance measurement of liquid particles is analyzed,and the main manufacturers and product types of liquid particle counters at home and abroad are introduced.The research background,purpose and significance of the portable liquid particle counting system are given,and the main content of this research is determined.Chapter 2: The overall scheme of the particle counting system based on the principle of photoresistance method is described.According to the design indicators of the liquid particle counting system,using modular design ideas,the system is divided into 7 modules including hydraulic module,sensor module,comparison counting module,controller module,stepper motor drive module,power module and input and output module.The optical path,the size of the sample circulation chamber,and the mechanical structure of the sensor were designed in detail,and the models and installation methods of the components in the optical path were determined.Chapter 3: The hardware circuit of the liquid particle counting system is designed.The i CWKL driver chip is used to drive the laser diode to achieve constant power control.The signal processing circuit of the sensor uses a transresistance amplifier circuit to convert the current signal of the laser diode into a voltage signal,a unit KRC filter circuit to remove high frequency noise,and a differential amplifier circuit to extract the signal and amplify it by 30 times.A circuit model was built in Multisim,and the signal generated by 4μm particles was simulated with a pulse current source to verify the correctness of the signal processing circuit.The main control circuit board integrates 6 comparison and counting circuits to process the sensor signals.The touch screen of Siemens is selected,and the communication between the lower computer and the upper computer is realized by RS485 communication.Chapter 4: Software system of the particle counting system is developed.The software system is mainly divided into two parts: the upper computer program and the lower computer program.The upper computer program is a human-computer interaction interface program through which the user sends instructions to the system and reads the test results.The lower computer program is an embedded system program,which drives the specific hardware to run according to the received upper computer instruction,and collects the counting result of the external counter.Chapter 5: Error analysis and experiment research is carried out.According to the system composition,the installation error,rotational speed error,volume error and voltage error are analyzed,and it is concluded that the system error mainly comes from volume error and voltage error.The theoretical maximum volume error of the system is 0.14 m L.The signal processing circuit theoretically generates a maximum voltage error of 16.2m V.The function test carried out size calibration experiment and flow limit experiment.The relationship between particle size and voltage threshold was calibrated using MTD oil-based standard particulate materials.The reasonable range of the working flow of the counting system is 12～24m L/min.Chapter 6: Summary and Outlook.The research progress and results of the particle counting system are summarized,the focus of further research is pointed out,and the future research work is put forward.