Research On Infrared Oil Detector

Under the rapid development of the national economy,the pace of industrial production is accelerating,and the problem of water pollution is becoming more and more serious.According to statistics,the total amount of petroleum materials flowing into rivers,lakes and seas through industrial wastewater discharge and mineral leakage can reach as many as 10,000 tons per year.The diffusion of heavy oil into water can directly cause the death of fish,shrimp and plankton.Besides,crops will be polluted and human health will be endangered,when water contaminated by petroleum minerals seeps into the ground.In a word,the detection of petroleum substances in water is of great significance.Now,petroleum determination methods include gravimetric method,ultraviolet spectrophotometry,fluorescence method,non-dispersive infrared photometry and infrared spectrophotometry.Among them,the gravimetric method is to extract oil by the organic extracting agent,but it will lost the oil component having a boiling point lower than the extracting agent.In addition,the operation of this method is complicated and is not suitable for the determination of a large number of samples.Ultraviolet method and fluorescence method will reduce the accuracy of measurement results greatly because of the large difference in absorption of water with complex composition.Infrared photometry is divided into non-dispersive infrared photometry and infrared spectrophotometry,both of which use the characteristic absorption peaks of infrared light of specific components in oil to determine oil content in water.Infrared spectrophotometry compared with non-dispersive infrared photometry,can accurately determine both alkanes and aromatic hydrocarbons in oil without being affected by the composition of water.Therefore,infrared spectrophotometry is used as the principle of the oil detector in this subject.The general design of the infrared oil detector is that the light source modulates the optical signal into the pulse light signal through a chopper driven by a stepper motor.And the pulse light signal forms the spectrum through the dispersion of the grating inside the monochromator,and stepper motor can change the grating’s angle.The monochromatic light with the specific wavelength is selected through the slit of the monochromator and sent into the sample pool.After absorbed by the reagent in the sample cell,the transmitted optical signal is converted into electrical signal by the pyroelectric sensor.The electrical signal is sent to the master chip LPC2136 via the preamplifier module and the signal processing module.After calculation by the master chip,the oil concentration in the sample can be obtained.In addition,the master chip LPC2136 can communicate with the host computer through serial port.In the preamplifier circuit module of pyroelectric sensor,the signal is output in the form of current,which improves the anti-interference ability of the signal.In the signal processing module,the combination of phase sensitive detection and dual-channel ideal integration is used to improve the signal-to-noise ratio of the signal and the scanning speed of the instrument to the reagent in the sample cell.The experimental data shows that the system has simple operation,good stability and high measurement accuracy,which can meet the national requirements for oil detection in water quality.