Design of precise gas monitoring system based on SGAS707 gas sensor

Chemiresistive sensors offer an affordable and effective way to measure gas concentrations in industrial control, HVAC systems, and health and safety applications. These sensors typically rely on a heating element to activate the sensing material, which means that developers must not only accurately measure the sensor’s resistance but also maintain precise temperature control for reliable performance. To meet these two key requirements, engineers have several design options that balance complexity with accuracy. This article explores the characteristics of chemiresistive sensors and their role across various applications. It introduces the Integrated Device Technology (IDT) chemical gas sensor family and delves into the specific requirements for using these sensors, along with analog design solutions that support their operation. Finally, we present a general microcontroller-based design approach and highlight the development boards and software tools available for evaluating and building gas sensor systems. **Precise Sensor Performance** As both qualitative and quantitative gas detection becomes more essential in professional and everyday settings, the need for accurate sensors is growing. Methane detectors are vital in mining environments, hydrogen sensors can warn users about battery issues, and advanced gas sensors can act as "electronic noses" in medical diagnostics. In residential and commercial buildings, the ability to monitor gas levels helps detect toxic substances and provides early fire alerts. Among the many types of gas sensors available, chemiresistive metal oxide sensors stand out for their cost-effectiveness and reliability, even in harsh conditions. These sensors work by detecting changes in resistance caused by variations in the concentration of airborne gases. The resistance change can be significant—often spanning multiple orders of magnitude within the sensor’s operating range. The relationship between the sensor resistance (RS) and the gas concentration (C) can be described by a simple equation involving two constants, A and α: $$ R_S = A \cdot C^\alpha $$ Alternatively, this can be expressed in logarithmic form: $$ \log(R_S) = \log(A) + \alpha \cdot \log(C) $$ This linear log-log relationship shows that resistance changes rapidly at low gas concentrations, but less so at higher levels. However, the support circuitry used in real-world implementations may introduce nonlinearities that affect measurement accuracy. Figure 1 illustrates how IDT's SGAS701 hydrogen sensor and other chemiresistive sensors exhibit a linear log-log response between resistance and gas concentration. Yet, external circuitry can distort this linearity. IDT offers a wide range of chemiresistive sensors for different gas detection needs, including: - Hydrogen: Using the SGAS701 sensor - Volatile Organic Compounds (VOCs): Using SGAS707, including formaldehyde, toluene, acetone, and alcohol - Flammable gases: Using SGAS711, such as hydrocarbons, methane, propane, and natural gas These four-pin devices integrate a resistive heating element that brings the sensor to its optimal operating temperature. For developers, the challenge lies in accurately measuring the sensor's resistance while maintaining the correct temperature. By employing various techniques, they can achieve a good balance between design complexity and measurement precision.

Ultra Thin Switch Power Supply

Switch Power Supply,Switch Mode Power Supply,Switch SMPS LED Power Supply,Ultra Thin Switching Power Supply

FOSHAN SHUNDE KELICHENG POWER SUPPLY TECHNOLOGY CO., LTD , https://www.kelicpower.com