A Setup for Measuring the Centering Error of a Dual-Element Pyroelectric Infrared Sensor Module.

This paper presents an experimental setup to measure the horizontal centering error of a pre-built pyroelectric infrared (PIR) sensor module, in which a dual-element PIR sensor is aligned at the focal point of a single-zone Fresnel Lens. In the setup, the sensor module was placed facing a modulated infrared radiating source and turned over a range of horizontal angles. The position of the optical axis of the sensor module was determined based on the analysis of the output response of the sensor at turned angles. Thus, the horizontal centering error of the module is defined as the difference between the mechanical axis of the housing and the found optical axis. For the prebuilt sensor module, with the specific available equipment, the measurement of the centering error of the module achieved a resolution of 0.02 degrees.

Scalable fabrication of high-performance NO2 gas sensors based on tungsten oxide nanowires by on-chip growth and RuO2-functionalization.

The on-chip growth and surface-functionalization have been recently regarded as promising techniques for large-scale fabrication of high performance nanowires gas sensors. Here we demonstrate a good NO2 gas-sensing performance of the tungsten oxide nanowires (TONWs) sensors realized by scalable on-chip fabrication and RuO2-functionalization. The gas response (Rg/Ra) of the RuO2-functionalized TONWs to 5 ppm of NO2 was 186.1 at 250 °C, which increased up to ∼18.6-fold compared with that of the bare TONWs. On the contrary, the responses of the bare and functionalized sensors to 10 ppm of NH3, 10 ppm of H2S and 10 ppm of CO gases were very low of about 1.5, indicating the good selectivity. In addition, the TONW sensors fabricated by the on-chip growth technique exhibited a good reversibility up to 7 cycles switching from air-to-gas with a response of 19.8 ± 0.033 (to 1 ppm of NO2), and this value was almost the same (about 19.5 ± 0.027) for 11 cycles after three months storage in laboratory condition. The response and selectivity enhancement of RuO2-functionalzied TONWs sensors was attributed to the variation of electron depletion layer due to the formation of RuO2/TONWs Schottky junctions and/or the promotion of more adsorption sites for NO2 gas molecule on the surface of TONWs, whereas the good reversibility was attributed to the formation of the stable monoclinic WO3 from the single crystal of monoclinic W18O49 after annealing at 600 °C.