A complete gas-sensing system for portable ambient monitoring purpose, consisting of a sensor (with embedded heater and thermometer) and an integrated interface (with read-out channel and closed-loop temperature control circuit) is presented. The micromachined sol-gel tinoxide sensor features a 450 nm thick silicon nitride/oxide membrane, an active area of 170 μmu; m × 170 μmu; m and a power consumption of 25 mW at 350 °C in isothermal operation. The read-out circuit uses a current integration and resistance-to-frequency conversion, providing digital output. The sensor is biased with a constant voltage and its temperature is regulated by an on-off closed-loop control circuit, consisting of a thermometer conditioning network, an A/D converter and a digital control block that drives the onchip output p-MOS power stage. The circuit can operate with different sensors to grant maximum flexibility. Chemical measurements with different gases have been performed, operating the sensor at different temperatures. © 2008 IEEE.
Lombardi, A., Bruno, L., Grassi, M., Malcovati, P., Capone, S., Francioso, L., et al. (2008). Integrated read-out and temperature control interface with digital I/O for a gas-sensing system based on a sno2 microhotplate thin film gas sensor. In Sensors, 2008 IEEE (pp.596-599) [10.1109/ICSENS.2008.4716510].
Integrated read-out and temperature control interface with digital I/O for a gas-sensing system based on a sno2 microhotplate thin film gas sensor
BASCHIROTTO, ANDREA
2008
Abstract
A complete gas-sensing system for portable ambient monitoring purpose, consisting of a sensor (with embedded heater and thermometer) and an integrated interface (with read-out channel and closed-loop temperature control circuit) is presented. The micromachined sol-gel tinoxide sensor features a 450 nm thick silicon nitride/oxide membrane, an active area of 170 μmu; m × 170 μmu; m and a power consumption of 25 mW at 350 °C in isothermal operation. The read-out circuit uses a current integration and resistance-to-frequency conversion, providing digital output. The sensor is biased with a constant voltage and its temperature is regulated by an on-off closed-loop control circuit, consisting of a thermometer conditioning network, an A/D converter and a digital control block that drives the onchip output p-MOS power stage. The circuit can operate with different sensors to grant maximum flexibility. Chemical measurements with different gases have been performed, operating the sensor at different temperatures. © 2008 IEEE.
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