GRAPHICAL METHOD FOR DETERMINATION OF MQ-SERIES GAS SENSOR CIRCUIT PARAMETERS FOR A STANDALONE GAS ALARM SYSTEM

Abstract

MQ-series gas sensors belong to the metal oxide semiconductor (MOS) family of sensors that can sense the presence of many gases. These sensors find their application in gas alarm systems as key components. While necessary sensor circuit output voltage value for alarm point in a standalone gas alarm system is desirable, but what exact combination of the sensor circuit parameters is required? Hitherto, the determination of these circuit parameters has not been much attention in the research community. This study explores a structured graphical approach of determining MQ series gas sensor circuit parameters for a standalone gas alarm system that yields the desired sensor circuit output voltage value for the alarm point. Model equations were developed for the sensor dynamics, and based on these model equations, graphs for the determination of required sensor parameters were plotted for a case of MQ-4 gas sensor response to liquefied petroleum gas (LPG). A structured graphical approach for determining MQ-series gas sensor circuit parameters for alarm points in a standalone gas alarm system showed that using MQ-4 gas sensor and LPG as the target gas. For a sensor circuit output voltage of 2 V for alarm point at 1000 ppm of LPG, the corresponding value of RO, RS, and RL obtained were 20 kΩ, 30 kΩ, and 20 kΩ, respectively. Hence, the developed structured graphical approach is suitable for determining MQ series gas sensor circuit parameters for a standalone gas alarm system under the influence of its associated gases.