Study And Design On An Infrared Refrigerant Leak Detector

In refrigeration systems, refrigerant leakage is a common symptom. Refrigerant leak will not only cause damage to the refrigeration equipment, result in economic losses, but also damage the Ozonosphere, lead the greenhouse effect and other environmental problems, brings many adverse effects to people’s normal life and production.For the problems of the refrigerant leak, we studied and designed a refrigerant leak detector. This leak detector is based on the infrared spectrum absorption techniques and used for detecting leaks on R12 and R134a and its detection sensitivity is 6g/year.The main contents of this paper are:1、We established a model for infrared spectrum absorption. Based on the infrared absorption theory, we used single beam dual-wavelength measurement to build an infrared absorption spectrum model. And then we deduced an algorithm which applies to this leak system.2、We presented the overall design scheme of infrared gas sensor. Infrared sensor consists of an IR source, a gas absorption chamber and an IR detector. Based on the requirements of sensitivity, we designed the size of the chamber and selected two infrared filets which were able to cover the absorption spectrum of R12 and R134a respectively. And then we selected the IR source and infrared detectors for the sensor. At last, we defined the modulation frequency of the IR source.3、Based on the requirements of the system, we took modular concept and designed hardware circuits and software parts of this detection system. The hardware circuits include power supply circuit, modulation circuit for infrared light source, signal processing circuit and the master processing circuit. We selected ADμC842 microcontroller as the core of the master processing circuit. And then we designed peripheral circuits such as pump control circuit, LCD display circuit, key detection circuit, sound and light alarm circuit and serial communications circuit. On the software front, the functions of system initialization module, data acquisition and processing module, the leakage determination module and each peripheral module are realized by C and assembly language.