The Study And Design Of Portable H₂S Detector Based On Electrochemical Sensor

In recent years, with the development of industry, poisonous gases andflammable gases in the air are increasing gradually. The influence of environment, thequality of life and personal security is becoming more and more serious. Therefore,detection of poisonous becomes a hot research area.In fact, H₂S is known to people in daily life, it appears in Night Streeteverywhere, many street traders use Gas-Lights which give off gases including H₂S toilluminate the road. The H₂S gives off a strange odour, which is so called ‘the smellyegg smell’. H₂S is a kind of nevus toxic, a suffocating and stimulating gas. It mainlyattacks central nervous system and respiratory system, also does harm to heart andother organs. The most sensitive parts are cerebrum and membrane. The toxicity ofH₂S will be influence by the concentration and the contacting time, the moreconcentration and contact time, the more restraining on the central nervous system.Even with a low concentration, the stimulation to mucous membrane will be also veryobvious. If a people accidentally have a long-time exposing to H₂S, it will cause greatdamage to the body organization and mechanism, and even death. Nowadays, peoplegradually realize the importance of environmental protection, so the gas detection. Ithas a large market space in portable gas detectors.There is variety of gas sensors, such as semiconductor sensor, catalyticcombustion sensor, infrared absorption sensor, electrochemical sensor and so on.These sensors are different of working principles, some have high sensibility, somehave high accuracy, and some have a low price. The existing H₂S detectors have alarge amount, but most of them are too expensive, not all ordinary people can accept.The others only have low accuracy and sensibility, can be only used for alarming.Only electrochemical sensor has a high efficiency-cost. The detector is designed based on electrochemical sensor, which has a smallsize that it can be portable, real-time detection, lower price, and operates simply. Itcan detect a small amount of H₂S concentration.The design uses STC12C5A60S2as the main MCU, which has a fastcalculation speed, has enough outside interfaces and has powerful anti-jammingability. The gas sensor is ME3, an electrochemical sensor. After acquiring signal dataof gas, making I/V transform, the signal will be amplified, and passed to ADC chip.The ADC modulates the analog signal onto digital signal, and then passes the signal tothe MCU to process. Lastly, the detector has a long-press POWER/END key, and candisplay temperature and humidity. With the DS1302, it can all display the present timeand date. These all use OLED screen to display.The software of the design in this paper use reduced instruction, from thedrivers of the bottom, and secondly the data processing, lastly, the result display, theseare all use short sentences to complete the programming.After a lot of practice and data, the design has proved successful. It isapplicable for the detection of H₂S, which meet the basic function requirement.