Fig. 1. Structure of chlorine gas sensor
When the sensor works, the relation between electrolysis current and chlorine gas density is shown as follows [5]:
displays them on the screen and sends them to the control center by GPRS. The host control instrument can store and display the historical data of concentration of chlorine gas with the SD card. The control center can analyze and store the data. The detecting range is 0~20ppm. When the concentration of chlorine gas is over-standard, the host control instrument will give alarms and sending signals to the control center. Therefore, this system can prevent the accident of chlorine leakage and guarantee the safety of workers.
4. Hardware system design4.1. Host instrument hardware system design
Fig 3 shows the hardware structure of host
i = F • A • D • C • n
σ
i -electrolysis current;
A -diffusing surface area; F -Faraday's number;
D -gas diffusion coefficient;
(1)
instrument. It contains processor, RS485 module, SD
card module, Alarm module, GPRS module, human- machine interface module and RTC (real time clock) module. The kernel processor adopted is MSP430F169, witch contain 60KB+256KB FLASH, 2KB RAM, 2 channels of USART and other modules. MSP430 series MCU is 16 bit RISC processor, which are widely
C -chlorine in the electrolyte solution, which has
a relation with the chlorine in the air with a direct ratio ;
σ -diffusion layer thickness;
n -electrons of unit weight chlorine gas.
3. General structure of the system
Fig. 2. General structure of the system
The whole chlorine gas online detect system can be divided into two parts: the chlorine gas online detect device and the control center. The chlorine 原文请找腾讯752018766优,文-论'文.网http://www.youerw.com gas online detect device can also be divided into host control instrument and chlorine gas transmitter. Fig 2 shows the general structure of the system. Several chlorine gas transmitters are settled in the monitoring area, detecting the concentration of chlorine gas and send the results to the host control instrument by RS485. The host control instrument collects the data of concentration of chlorine gas sending from transmitter,
used in instruments, automatic control and consumer electronics. They have the advantages of high speed, low power, powerful functions, strong anti-interference and hard to decode.
Fig. 3. hardware structure of host instrument
4.1.1. RS485 interface design. The host instrument connects with chlorine gas transmitter by RS485 bus. It allows up to 128 devices on the bus and easy to be built as a network.
Fig. 4. RS485 module interface
4.1.2. SD card interface design. SD card is a memory