Pulsed-Temperature Metal Oxide Gas Sensors for Microwatt Power Consumption

Abstract

Metal Oxide (MOX) gas sensors rely on chemical reactions that occur efficiently at high temperatures, resulting in too-demanding power requirements for certain applications. Operating the sensor under a Pulsed-Temperature Operation (PTO), by which the sensor heater is switched ON and OFF periodically, is a common practice to reduce the power consumption. However, the sensor performance is degraded as the OFF periods become larger. Other research works studied, generally, PTO schemes applying waveforms to the heater with time periods of seconds and duty cycles above 20%. Here, instead, we explore the behaviour of PTO sensors working under aggressive schemes, reaching power savings of 99% and beyond with respect to continuous heater stimulation. Using sensor sensitivity and the limit of detection, we evaluated four Ultra Low Power (ULP) sensors under different PTO schemes exposed to ammonia, ethylene, and acetaldehyde. Results show that it is possible to operate the sensors with total power consumption in the range of microwatts. Despite the aggressive power reduction, sensor sensitivity suffers only a moderate decline and the limit of detection may degrade up to a factor five. This is, however, gas-dependent and should be explored on a case-by-case basis since, for example, the same degradation has not been observed for ammonia. Finally, the run-in time, i.e., the time required to get a stable response immediately after switching on the sensor, increases when reducing the power consumption, from 10 minutes to values in the range of 10-20 hours for power consumptions smaller than 200 microwatts.

RHINOS: A lightweight portable electronic nose for real-time odor quantification in wastewater treatment plants

“…In a medium-term future, the above tasks could be carried out semi-autonomously (with limited human intervention) or fully autonomously thanks to map-based ( Burgués et al., 2019 ) or bioinspired ( Harvey et al., 2008 ; Lochmatter, 2010 ; Neumann et al., 2013 ) search strategies. For that to become a reality, more research on techniques to improve the performance of low-cost gas sensors is encouraged, especially in terms of response time, sensitivity ( Dey, 2018 ; Wang et al, 2010 ), and power consumption ( Burgués and Marco, 2018 ; Palacio et al, 2020 ).…”

Sniffing speeds up chemical detection by controlling air-flows near sensors

“…The sensor section incorporates 4 TGS sensors per board in series for a total of 16 sensors. The board draws ~700–800 mA and is kept powered on before and after each measurement test to elude transient unstable response that appears when power is applied to the sensor when it was unpowered for some time 59 , 60 . In our experiments, we run the sensors at a voltage of 5.6 V. Last is a section for the test sample to be placed where the headspace is in series with the flow.…”

Development of compact electronic noses: a review

“…Usually, the research work using the PTO schemes applies the waveform to the heater for a few seconds, and the duty cycle exceeds 20%. Palacio et al [142] explore the behavior of PTO sensors working under aggressive schemes, which achieves a 99% power saving effect compared to continuous heater stimulation. Using the sensor sensitivity and detection limit, they evaluate four ultra low power sensors under different PTO schemes exposed to ammonia, ethylene, and acetaldehyde.…”