Study On Near Infrared Fast Humidity Measuring System

The determining of the moisture content and control in many fields are of great importance for the condition testing and the product quality control and is closely related to mankind.Compared with the traditional humidity measuring means, near infrared humidity measureing method overcomes the disadvantages of common method and the humidity can be inspected uninterruptedly, untouchedly, great range, fast and high stability, high selectivity if the infrared detector is used in the industry process.Because of its high ratio of property to price in the humidity measuring field,so that it is supposed to have the huge application development potential in people's daily life and producing activities.This paper introduces the actuality about the measurement of humidity firstly. Then the whole bag of tricks is discussed.Based on the principle of the Beer-Lambert Law, this system detects water vapor gas by means of double wave bands. According to the varying relationship of two wave bands, the system determines the density of this measuring gas. Moreover it cuts down on the interference brought by surroundings utilizing double wave bands. Secondly, this paper introduced the design of hardware circuit and software program design in detail and central flow chart. The system is mainly composed of infrared detector structure and hardware circuit.In the detector part, the selection and design of the optical source, reticule and infrared detector are taken over. Besides, this paper analyzes and controls the factors which can influence signal to noise ratio of the system in the design.The hardware circuit mostly includes preamplifying circuit, bandwidth limited circuit, A/D translation circuit, sound alarm circuit, display circuit and other parts.In software design, using structured programming namely modular language to design software. The applied software is made up of several parts as following: main program flow, initial subprogram flow, digital filtering subprogram flow, concentration disposal subprogram flow, upper and lower alarm subprogram flow and so on.In the end, by analyzing the factors that affect and determine the system, it prefers the ways to improve the function and performances of system, and makes the discussion to the system reliability design which can decrease the environmental interference and misinformation of alarm...