Development Of Capacitance Sensor For Oil Online Monitoring And Research Of Online Test Method

The expense of lubricants is very small in the large costs using in the maintenance of equipment in the enterprise , but its fuction is extremely importnat.Perfect lubrication requires rational use of lubricants, working conditions of lubricants should be monitored at any time to ensure reasonable time of oil replacement, safety and effectiveness of lubrication have been ensured. Oil monitoring technology monitor primarily physical and chemical properties of oil and content of abrasive, working conditions and oil pollution of equipment monitored can be timely understanded, according to the quality of oil replace old oil and predictive Maintenance. The technology is now increasingly more enterprises attach importance to developing a variety of oil monitoring instrument.Lubricating oil is a complex mixture, it can be seen as a weak polar liquid dielectric, the dielectric constant is about 2.0. When machinery impurities, acidity, moisture content, and other pollutants in oil changing, the dielectric constant of oil will be corresponding changes. Based on the theoretical analysis of lubricants on-line monitoring of dielectric method, combining the advantages of capacitive sensors, from the perspective of industrial applications, a new type of two pairs of semi-circular plate staggered capacitance sensors has been designed,thus avoiding the plate caused by deposition of pollutants decreases sensor sensitivity and ease of cleaning, and other traditional oil monitoring capacitance sensor disadvantages. Oil dielectric constant change by monitoring can be informed of oil pollution and decay, achieve the purpose of on-line monitoring of lubricants being used.According to the basic theory of electromagnetic fields, calculated theoretically capacitance value of sensor and the charge density of plate, using ANSYS software, potential and the field intensity of the sensor distribution are analyzed, and found that the sensitivity of the internal distribution of testing field is uniformity. To obtain testing Field to be uniform and high sensitivity, and ensure that measurement of oil pollutants content will not be affected by flow pattern and distribution of oil, structure and size of sensor has been optimized.Detection and alarm circuit based on CAV424 and AM402 has been designed, capacitance change of sensor can be translated into 4 to 20 mA current facilitate the transmission in industry, to monitor oil pollution and decay. Using this sensor developed by the Subject, study relationship between major pollution (water, acid, metal debris) in oil and the dielectric constant changes, plot curve of the relationship by applying MATLAB software, and determine oil lubricants pollution Alarm thresholds.The sensor developed by the subject apply to large equipment and large vehicles requiring continuous work and poor working environment. It has the advantages of small size, low cost, simple operation, easy installation and on-line measurement.