| As ozone is significant to kill bacteria and fungi, inhibiting the growth of viruses, stimulating blood circulation, low cost of treatment and few side effects of drug treatment, the medical application of ozone in the clinical treatment has been a great success, with the progress of modern science and technology.Medical ozone therapy instrument is generally composed of high-voltage generator, ozone concentration detector, gas controller about quality and flow, catalytic decomposition of ozone device disposable ozone dissolved device and electrical control system. Further more, the concentration detector has four parts, which are concentration sensor, temperature and humidity sensor, MCU and external circuits.In this paper, we use a sensor of double optical paths ultraviolet adsorption spectrometry to detect the concentration of ozone in a mixture of ozone and oxygen, and turn the gas concentration signals into electrical signals. First, the mixture of gas is sent into a chamber for measuring. Then a beam of UV issued by a UV light launch into the chamber after launch through a instrument which can adjust the scope of wavelength of the beam. After passing through two rotating UV filters, the UV beam is filtered other wavelength and only left two special UV beams for measuring and correcting, the center wavelength of which are 254nm and 210nm, with a half-width of 100nm. These two sampling signals are converted into electrical signals as U1 and U2 by a photoelectric instrument.The voltage is amplified and adjusted by AD623 amplifier. Then the adjusted signal can be turned into digital signal, which can be identified by MCU only after AD conversion. System adopts TLC2543 as AD conversion chip, which is 12 bit high precision AD chip. TLC2543 has 11 analog input channels and its communication with MCU via a serial way that can save resource of MCU very much. Its conversion time is just 10μs so that it doesn't need external sampling keeping circuit. The calculate core of system is STC89C58, which has 32KB FLASH memorizer that can support ISP function. This chip can download program via RS-232 serial port without special programmer that is easy for programming and testing. It also has 1280B RAM and 16KB E2PROM. In addition, it has soft watchdog and low power design. Human interface with the computer uses SMG12864ZK Chinese characters LCD display module and 2*2 keyboard which contains of mode key (MODE), plus key(+), subtract key(-) and enter key(ENTER). The system can switch in different modes with those control buttons, and alarm value can be realized the dynamic setting. The system place an RS-232 serial port to communicate with the external. As the only communication port of system serial port is very important. With the serial port, we can use the computer on-line to set up the alarm value online, and order MCU to show the gas concentration of environment as well as the alarm value which is already set up. Acousto-optic alarm module adopt alarm buzzer and three color LED to display the state of system and gas concentration.The software of system is compiled with C51 compiler system. And the main program has been divided into several sub-module. The major functions of software are such as setting initial state of the system, identification of gas concentration, temperature and humidity measurement, compensation to the gas concentration according to the temperature and humidity, serial communications, scanning keyboard and model choice, displaying the gas concentration, acousto-optic alarm and so on. Interrupt service routine of timer 0 is the core of the system, because many of the major functions are embedded in the interrupt service routine. The time that timer 0 set up is 50ms, which means main function will have a routing cycle per 50ms. Interrupt service routine includes ozone detection subroutine, the detection subroutine of temperature and humidity, correcting subroutine for gas concentrations, dynamic setting subroutine for alarm value, change display, trigger watchdog and so forth. Serial communication module is also a key of the system, whose communication protocol has been drawn for facilitating the continued development and application of system upgrading. To enhance system reliability, we will set up timer 2 through software to achieve watchdog function, trigger watchdog on time and correct to avoid program error.The test of system is carried out at an O3 environment. Based on the contrast of actual gas concentration and the measured gas concentrations, the system basically accord with the design requirements. It can be achieve rapid and accurate response to ozone. |
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