Temperature Dependence Of Sensors Research Articles

Offset Reduction in GMI-Based Device by Using Double-Frequency Bias-Current Modulation

In this paper, we investigate the effect of temperature variations on the off-diagonal giant magneto-impedance (GMI) response. This paper is based on a theoretical model describing the GMI-based sensor response. The modeling has been extended to include the resistivity dependence versus the temperature. It allows to calculate both temperature sensitivity and intrinsic magnetic field sensitivity, whose ratio leads to the determination of the magnetic field offset drift versus the temperature. Thanks to an original conditioning circuitry based on a double ac current excitation instead of the classical one, we achieved an improvement of the long-term stability and minimized the sensor temperature dependence. Experimentally obtained results have been compared with the expected offset drift for the classical GMI, and with the expected fluctuation reduction while adopting this technique, showing a relatively good agreement with the proposed modeling.

Coupled dark state magnetometer for the China Seismo-Electromagnetic Satellite

The coupled dark state magnetometer (CDSM) is an optically pumped scalar magnetometer, which is based on two-photon spectroscopy of free alkali atoms. This paper introduces the measurement principle, instrument design, required resources and key performance characteristics of the flight model for the China Seismo-Electromagnetic Satellite, which is the first demonstration of the CDSM measurement principle in space. The CDSM uses several coherent population trapping (CPT) resonances in parallel in order to reduce systematic errors, e.g. the sensor temperature dependence. Overall five control loops were identified to enable a reliable operation. As known so far CPT is the only effect in optical magnetometry which inherently enables omni-directional, dead-zone-free measurements. This leads to a simple all-optical sensor design without double cell units, excitation coils or electromechanical parts. The instrument is characterized by an accuracy of 0.19 nT (σ), a detection noise of 50 pTrms at 1 s integration time, a mass of 1672 g and an in-Earth orbit measured power consumption of 3394 mW.

Micro pH Sensors Based on Iridium Oxide Nanotubes

Iridium oxide (IrO x ) nanotubes have been grown on microelectrodes utilizing a patterned nanoporous aluminum oxide (AAO) template to form a micro pH sensor. A layer of 900-nm thick aluminum sputtered on a silicon wafer was locally anodized at various voltages to investigate the morphology of the patterned AAO templates. The electrode position of IrO x inside the supportive AAO template was carried out to yield IrO x nanotubes with a diameter ranging from 80 to 110 nm, corresponding to the AAO pore sizes. The fabrication processes produced free-standing IrO x nanotubes on top of the 50 × 100 μm 2 micro-scale electrodes. Material characterization along with fabrication parameters was investigated. Potentiometric responses of the miniature sensors to hydrogen ions in terms of sensitivity, repeatability, response time, and reliability were performed. Super-Nernstian response was achieved. pH measurements for higher resolution targeting biological applications and sensor temperature dependence were also conducted.

A Self-Referencing Intensity Based Polymer Optical Fiber Sensor for Liquid Detection

A novel self-referencing fiber optic intensity sensor based on bending losses of a partially polished polymer optical fiber (POF) coupler is presented. The coupling ratio (K) depends on the external liquid in which the sensor is immersed. It is possible to distinguish between different liquids and to detect their presence. Experimental results for the most usual liquids found in industry, like water and oil, are given. K value increases up to 10% from the nominal value depending on the liquid. Sensor temperature dependence has also been studied for a range from 25 °C (environmental condition) to 50 °C. Any sector requiring liquid level measurements in flammable atmospheres can benefit from this intrinsically safe technology.

Miniature temperature-insensitive Fabry-Pe/spl acute/rot fiber-optic pressure sensor

We present a miniature fiber-optic pressure sensor with a diameter of only 125 mum. The sensor works as an extrinsic Fabry-Peacuterot interferometer and the cavity length can be controlled with a resolution of about several nanometers. Also the sensor sensitivity can be easily adjusted by controlling the sensor gauge length. A passive temperature compensation scheme was used to reduce most of the sensor's temperature dependence. Since the sensor is composed entirely of fused silica, it is reliable, biocompatible, corrosion resistant, and immune to electromagnetic interference and has high-temperature capability