| Gas is everywhere in our natural environment, but some of these gases are beneficial to our lives, some are not. In order to effectively detect the specialty of various gases, the advanced and applicable gas sensors are thus needed. The design and implementation of gas-sensor dynamic testing system is to test the performance of gas sensors, allow gas sensors with superior performance to serve people from all walks of life, and improve people’s livelihood as well as production capacity.The gas-sensor dynamic testing system presented in this paper, shares with data acquisition, instrument control, and data analysis with the aid of virtual instrument technology, based on the Lab VIEW of US National Instruments. On the hardware side, the paper covers two parts, including dynamic gas distribution and system test circuit. The main purpose of dynamic gas distribution is to provide a changed gas concentration environment for gas sensors within a certain period. It comprises of gas source, gas circuit, gas mass flow controller, gas-mixing chamber and sensor test chamber. After completing the precise control of gas flow, we let test gas and background gas mix sufficiently, which smoothly flow in the sensor test chamber. The system test circuit aims to acquire the sensor’s signal value. It is composed of system operating circuit and matched resistance circuit. This test system sets a constant operating voltage to the sensor, and simultaneously making series connection with a matched resistance, allowing the resistance value of both matched resistance and the sensor to be as close as possible. Since the current is equal for the series circuit, only by measuring the voltage across the matched resistance, we can indirectly get the sensor resistance value and ultimately obtain the various performance parameters of the sensor. On the software side, the paper designs peripheral control, data acquisition and data analysis. Peripheral control is mainly for realizing software control towards gas mass flow controller and programmable DC power supply, thereby enhancing the automaticity of the entire test system. The purpose of data collection is to receive the real-time acquisition of the sensor signal value. We use the matched resistance automatic switch algorithms and data collection algorithms to complete the acquisition of sensor signal, and remove all kinds of noise and peak by means of the Lab VIEW digital filtering technique. Finally the curve and value are clearly displayed to the user. The data analysis is for analyzing various performance parameters of the sensor by saving acquired data. It uses the saved TDMS file to form two-dimensional graph of time and resistance value through curve-redrawn algorithm, over which with the help of the Lab VIEW cursor technique the sensor’s response time and the resistance sensitivity can be obtained. And this is also used to determine the merits of the sensor.The test system has the features of high test accuracy, high test efficiency, and also wide test range. The advanced hardware design philosophy and friendly interface engender the system to be extensively applied in production, scientific research and daily life, and offer more reliable performance parameters for gas sensors. |
