Design And Implementation Of A Portable Formaldehyde Gas Detector

With the acceleration of the domestic economic development, people's living standards are improving continuously and their room decorations are becoming diversified, too. The pollutants in the decorating materials are on the rise and the pollutants volatilized into the air severely endanger people's health, especially the decoration and the newly purchased furniture induced formaldehyde gas in the room air that exceeds the standard levels, which causes extremely severe harm to people's health. Swift and accurate detection of the formaldehyde gas in the room air becomes the important method for treating formaldehyde pollution. However, the main method for detecting the formaldehyde gas in the room air so far is conducting the analysis and experiments in the labs, which involves a complex process of detection in spite of the high accuracy. This method takes a long time to obtain the detection results and costs heavily. Therefore, designing cheap, operationally easy and portable on-the-spot online formaldehyde gas detectors for swift detection is in urgent need. In light of this, this paper chooses the design and realization of portable formaldehyde gas detectors as the research subject. A swift formaldehyde gas detector based on the electrochemical sensor was designed and through the study on the principles of the sensor's operation, the hardware system and the software system were designed and realized. Embedded technology was employed in the portable formaldehyde gas detector. Module design was used in the hardware system with the single chip as the control core of the system and the front-end signal acquisition circuit was designed. The main design modules included the constant electric potential circuit, the signal conditioning circuit, the A/D conversion module, the data processing module, the display module and the power supply module. Module design was used in the software design in which the data acquisition subroutine, the digital filter subroutine, the data processing subroutine and the data display subroutine were designed. In the digital filter subroutine, the method of limiting the average filtering was applied to dispose of the produced s ignal interference so as to enhance the accuracy of detection.In this paper, a novel electrochemical sensor of formaldehyde gas was adopted in the development of the portable formaldehyde gas detector, which could detect the formaldehyde gas accurately on the spot. The main work we finished was as follows:(1) Current studies on the formaldehyde gas detectors were reviewed and the application of the existing formaldehyde gas detectors and the shortcomings in it were analyzed, whereby the target of design o f the portable formaldehyde gas detector was determined and the requirements on the portable formaldehyde gas detectors was analyzed, including the analysis of the requirements on its performances and functions;(2) The overall design of the formaldehyde gas detector was completed by combining the requirements on the performances and functions of the portable formaldehyde gas detector, including the overall design of the hardware and that of the software.(3) The design of the hardware of the portable forma ldehyde gas detector was completed. Under the guidance of the overall framework for the hardware of the portable formaldehyde gas detector, the selection of the single chip, of the electrochemical sensor, the design of the constant potential, of the signal conditioning module, of the data acquisition circuit and of the power supply module were completed;(4) The design of the software of the portable formaldehyde gas detector was completed, mainly including the overall structural design of the software of t he formaldehyde gas detector, of the main routine, of the core function module and of the security. The focus was the completion of the design of the data acquisition, the digital filter, the data processing and the data display;(5) Through experiments, the function tests of the portable formaldehyde gas detector were completed.Therefore, the effectiveness and practicability of the portable formaldehyde gas detector's analog circuit, digital circuit and detection of formaldehyde were confirmed.Through the function tests of the portable formaldehyde gas detector, all the tests were conducted on all the function modules of the portable formaldehyde gas detector. During the tests, the basic functions of the portable formaldehyde gas detector were realized, all the non- functional requirements were met to satisfy the basis needs of users and the expected functions and the expected targets of stability, concurrency, security profiles, etc of the portable formaldehyde gas detector were realized. Embedded technology was employed in the portable formaldehyde gas detector to achieve the acquisition of data, processing of digital signals and the function of display. Besides, the top optimization design was achieved in its cost, power dissipation, volume, stability and so on. The development of the portable swift formaldehyde gas detector could reduce the cost of the lab-based air quality detection and the detection fees, boasting good social and economic benefits.Currently, the portable formaldehyde gas detector designed in this paper solves the problems of high costs, environmental tolerance, power dissipation, response time and so on very well. However, due to the fact that the sensor of the formaldehyde gas is easy to be interfered by such substances as ethanol and methanol, the portable formaldehyde gas detector currently in study can not solve the problem of selection very well. The characteristic parameters of the formaldehyde gas will be obtained in the future so as to solve the problem of other gases interfering with the detection of the formaldehyde gas. And, as the pollution of the formaldehyde gas in the room air is getting worse, finding the solution to formaldehyde pollution in the room air will also be the focus of our later work.