Using Smart Sensor Strings for Continuous Monitoring of Temperature Stratification in Large Water Bodies

A "smart" thermistor string for continuous long-term temperature profiling in large water bodies is described allowing highly matched yet low-cost spatial and temporal temperature measurements. The sensor uses the three-wire SDI-12 communications standard to enable a low-powered radio or data logger on supporting buoys to command measurements and retrieve high-resolution temperature data in digital form. Each "smart" temperature sensor integrates a thermistor element, measurement circuitry, power control, calibration coefficient storage, temperature computation, and data communications. Multiple addressable sensors at discrete vertical depths are deployed along a three-wire cable that provides power and allows data transfer at regular intervals. Circuit, manufacturing, and automated calibration techniques allow temperature measurements with a resolution of plusmn0.003degC, and with intersensor matching of plusmn0.006degC. The low cost of each sensor is achieved by using poor tolerance thermistor and circuit components in conjunction with a 15-bit charge-balance analog-to-digital converter. Sensor inaccuracies and temperature coefficients are corrected by a two-point calibration procedure made possible by a standard-curve generator within the sensor, based upon the method of finite differences. This two-point calibration process allows in-field sensor string calibration in stratified water bodies and provides a means to correct for long-term calibration drift without having to return the string to a laboratory     

A general method for calculating the uncertainty of virtual sensors for packaged air conditioners

Virtual sensors use data from low-cost measurements and calibrated models to provide outputs that would either be too expensive or impossible to measure directly. Virtual sensor technology has the potential to enable cost-effective implementation of advanced monitoring, diagnostic, and/or control features for buildings. While it is commonly known that the reliability of virtual sensors depends on the amount and conditions of calibration data, no methods have been presented that quantify the effect of the conditions of calibration data on virtual sensor output uncertainty. In this paper, a general method is presented for estimating the virtual sensor output uncertainty in terms of the uncertainty, conditions and amount of calibration data. The method is demonstrated with a power consumption virtual sensor for packaged air conditioning systems.     

Low-Power Printed Circuit Board Fluxgate Sensor

A new printed circuit board flat fluxgate sensor with integrated coils and amorphous alloy core was developed and its excitation parameters optimized for low-power consumption. The power consumption achieved with 10 kHz, 300 mA p-p pulse excitation with duty cycle 12.5% was only 3.9 mW, which is three times lower than that for sinewave B excitation. The sensor sensitivity reached 94 V/T. The required excitation bridge supply voltage was only 0.47 V. The low-cost low-power sensor has a temperature offset stability of 120 nT in the -20 to +70 degC temperature range and 0.17%/degC open-loop sensitivity tempco due to the use of a new core embedding technique. The perming error due to 10 mT field shock was suppressed below 1.2 muT. The short-time offset stability was 38 nT within 3 h. Thus the developed sensor is more precise and less energy consuming than a periodically flipped anisotropic magnetoresistance (AMR) sensor. The achieved parameters are sufficient for compass with 0.1deg error     

A CMOS Integrable Oscillator-Based Front End for High-Dynamic-Range Resistive Sensors

A new oscillating circuit is proposed to estimate the resistance and parallel parasitic capacitance of resistive chemical sensors. The circuit is able to reveal the resistance in a wide range (from tens of kiloohms to more than 100 $hbox{G}Omega$) due to the adopted resistance-to-time technique. In addition, the parallel capacitance (up to 50 pF) can be estimated. The circuit, which does not need any initial calibration, is very simple and compact and is suitable to be integrated with a standard CMOS technology to obtain a low-cost and low-power device for a sensor array interface. Different kinds of postlayout simulations concerning the CMOS integrated implementation have been conducted. Experimental results obtained using a discrete prototype board, both on passive components and on real sensors (metal–oxide sensors), have shown good linearity and reduced percentage error with respect to the theoretical expectations.      

Discontinuously Operated Metal Oxide Gas Sensors for Flexible Tag Microlab Applications

Micromachined silicon substrates have significantly reduced the heating power consumption of metal oxide (MOX) gas sensors. Specific applications, however, require further reductions far beyond the present state-of-the-art. In this paper, we report on discontinuously operated MOX gas sensors on micromachined heater platforms and show that such sensors allow power consumption levels to be reached which are consistent with Flexible Tag Microlab (FTM) operation. Such FTMs allow gas concentrations to be measured and recorded to reveal the transport history of goods along the logistics chain for later interrogation by a wireless reader.     

Low-Cost Surface-Mount LED Gas Sensor

A low-cost chemical sensor comprising surface-mount light-emitting diodes (LEDs) has been developed for colorimetric gas detection. The device consists of a pair of LEDs connected to a simple PIC microcontroller circuit and in the most basic form, requires the use of only two input–output (I/O) pins on the chip. The key features of this sensor are the use of a LED rather than a photodiode for light detection and an all-digital light detection protocol that leads to a reduction in cost and power consumption by avoiding the need for an analog-to-digital converter. The surface-mount diodes employed are more compact than standard LEDs and are more amenable to coating by solid-state sensor films. Results from sensors employing a chemochromic ammonia sensitive film are presented, and the detection of this target is demonstrated in the parts-per-million range. The configuration is applicable to a wide range of colorimetric gas sensing materials.     

Evaluation on Rain-Defense Performance of Temperature Sensors

Rain-defense performance of temperature sensors is of concern in many important fields, while there has been no suitable method to evaluate their performance before. To solve this problem, an experiment is described in this paper. The experimental device used is a conventional temperature calibration wind tunnel. To simulate the practical environment as rainfall of 8 mm per hour, a water tank is set above the open experimental section of the wind tunnel, at the bottom of which many small holes are drilled so that rain can run down. Three new-type temperature sensors and an old-type temperature sensor are calibrated in the wind tunnel. The calibration method is similar to the recovery characteristic and dynamic characteristic calibration except that the environment here is a mixture of spray and air. As the authentic total temperature is unable to be obtained, an equivalent recovery factor is defined, which uses the total temperature outside the calibrated sensor to participate in the calculation instead of the authentic local total temperature. And through dynamic characteristic calibration, the time constant of the sensor is also obtained. During the calibration experiment, the gas Mach number, water temperature, and attack angle of the temperature sensors are varied. The result shows that the equivalent recovery factor of the new sensor design is lower than that of the old sensor design, which proved that the rain-defense performance of the new sensor design is better than the old sensor design, and some other comparisons can also demonstrate this point. Associating the design structure of the temperature sensor with the experimental result, the evaluation method is shown to be reasonable and feasible.     

Decentralized random decrement technique for efficient data aggregation and system identification in wireless smart sensor networks

Smart sensors have been recognized as a promising technology with the potential to overcome many of the inherent difficulties and limitations associated with traditional wired structural health monitoring (SHM) systems. The unique features offered by smart sensors, including wireless communication, on-board computation, and cost effectiveness, enable deployment of the dense array of sensors that are needed for monitoring of large-scale civil infrastructure. Despite the many advances in smart sensor technologies, power consumption is still considered as one of the most important challenges that should be addressed for the smart sensors to be more widely adopted in SHM applications. Data communication, the most significant source of the power consumption, can be reduced by appropriately selecting data processing schemes and the related network topology. This paper presents a new decentralized data aggregation approach for system identification based on the Random Decrement Technique (RDT). Following a brief overview of the RDT, which is an output-only system identification approach, a decentralized hierarchical approach is described and shown to be suitable for implementation in the intrinsically distributed computing environment found in wireless smart sensor networks (WSSNs). RDT-based decentralized data aggregation is then implemented on the Imote2 smart sensor platform based on the Illinois Structural Health Monitoring Project (ISHMP) Services Toolsuite. Finally, the efficacy of the RDT method is demonstrated experimentally in terms of the required data communication and the accuracy of identified dynamic properties.     

基于动态可变阈值的低功耗单声道气体超声波流量计

为克服气体涡轮流量计存在压损和需定期校准的缺点,研制了耐高压低功耗单声道气体超声波流量计.针对换能器因阻抗不匹配造成的回波信号质量差的问题,分析了回波信号的特征,提出了动态可变阈值和过零检测的数字信号处理方法.该方法可精准定位回波信号特征点.研制了以STM32为核心的低功耗气体超声波流量变送器.变送器采用了新的激励方式...     

A Low-Cost Wireless Sensor System and Its Application in Dental Retainers

In this paper, a wireless interrogable sensor device based on an ultra low-power microcontroller for data collection and a radio frequency identification (RFID) interface for data transmission is presented. Wireless sensor systems utilizing RFID transponders offer a new and exciting means of measurement and identification suitable for many biomedical applications. For the majority of these applications, small, inexpensive radio request sensor systems are desirable. In this paper, an ultra-low-power and low-cost wireless temperature data logger system is presented with its application in observing dental retainer use. For this purpose, the retainer's ambient temperature is measured by an integrated sensor and recorded using a microcontroller which acts like a temperature data logger storing the thermal history of several months. For a self powered wireless data transmission from the sensor to the interrogation unit a RFID transponder, operating in the 13.56 MHz ISM band, is used. The presented sensor system includes hard- and software power saving modes reducing the sensor idle current consumption to 1 $mu$ A. This allows a battery powered operation of the device for up to two years. For dental and biomedical applications, the device is hermetically sealed using a biocompatible polymeric encapsulation. Results of the first clinical trials observing the patient's dental retainer usage by a set of retainers equipped with the RFID temperature sensor/data logger device are presented. The stored temperature values are analyzed and a clear temperature characteristic indicating the retainer usage was found.      

水声传感网中的高效调制解调器的设计

为适应水声传感网络节点密集、规模大、工作时间长的特点,提出了一种具有小体积、低成本、低功耗等特点的水声调制解调器。采用数字幅度调制2ASK调制解调方式,硬件使用低功耗设计方案,电池供电,使用市场上量产的收发一体式小型水声换能器,使功耗和成本得到大幅度降低。经实际测试,整机最大功耗为90 mW,数据传输速率为2kbps,具备代替市场上昂贵水声调制解调器的潜力,在水声传感网技术中有良好的应用前景。     

Temperature profile investigation of SnO/sub 2/ sensors for CO detection enhancement

SnO/sub 2/ sensors are widely used for the detection of air contaminants such as CO. Nevertheless, their application encounters several problems, mainly the effect of interfering gases. The low selectivity is, in fact, a well-known problem of these sensors. Moreover, the high operating temperature of metal oxide sensors implies, in general, high power consumption. We present a study aimed at the selection of an appropriate measurement technique for detection of CO for indoor applications (lower threshold 100 ppm), in the presence of high concentrations of ethanol (up to 1000 ppm), by using only one sensor. Moreover, the paper aims at developing portable CO detectors that are very small, low power, and could be battery operated.     

Transparent network for hybrid multiplexing of fiber Bragg gratings and intensity-modulated fiber-optic sensors

A network for multiplexing fiber Bragg gratings (FBGs) and intensity-modulated fiber-optic sensors with no need to distinguish between the two kinds of sensor is proposed and experimentally demonstrated. Two FBG sensors and two intensity-modulated sensors are wavelength-division multiplexed; the electrical phase of the output signal is measured as a common parameter for both types of sensor. Furthermore, the intensity sensors become power referenced, and the FBG sensors are interrogated by a low-cost technique. Low cross talk is achieved by use of a tunable optical filter at the detector.     

A Nanowatt Smart Temperature Sensor for Dynamic Thermal Management

The amazing integration densities achieved by current submicron technologies pay the price of increasing static power dissipation with the corresponding rise in heat density. Dynamic Thermal Management (DTM) techniques provide thermal-efficient solutions to balance or equally distribute possible on-chip hot spots. Accurate sensing of on-chip temperature is required by optimally allocating smart temperature sensors in the silicon. In this paper, we introduce an ultra low-power (1.05–65.5 nW at 5 samples/s) tiny (10250 $mu {rm m}^{2}$) CMOS smart temperature sensor based on the thermal dependency of the leakage current. The proposed sensor outperforms all previous works, as far as area and power consumption are concerned (more than 85% reduction in both cases), while still meeting the accuracy constraints imposed by target application domains. Furthermore, a specific interface based on the use of a logarithmic counter has been implemented to digitalize the temperature sensing. These facts, in conjunction with the full compatibility of the sensor with standard CMOS processes, allow the easy integration of many of these tiny sensors in any VLSI layout, making them specially suitable for modern DTM implementations.      

一种表面温度传感器的校准系统

本文介绍了一种表面温度传感器的动态校准系统，对动态校准的过程作了简单的描述，并着重描述了系统静态标定的过程，文章最后还给出了对一种表面温度传感器的系统静态标定的结果。     

Low-Power and Low-Cost Implementation of SVMs for Smart Sensors

In this paper, we propose an efficient implementation of support vector machines (SVMs) on a low-power and low-cost 8-bit microcontroller. The proposed solution can be advantageously used to implement smart sensors and sensor networks for intelligent data analysis and pervasive computing. A new model selection algorithm that allows fitting the resource constraints imposed by the hardware architecture is proposed. Moreover, the performance of an optimized implementation which exploits the CORDIC algorithm is detailed and discussed     

蓝宝石光纤黑体腔传感器定度技术研究

基于Planck辐射原理和光纤测温技术的溅射高温陶瓷薄膜的蓝宝石光纤黑体腔传感器可进行恶劣环境下瞬态高温的测量。本文介绍了该传感器的结构和用来对其进行定度的系统,将已标定的钨铼热电偶和被定度的瞬态表面高温传感器同时置于乙炔焰热源所形成的高温均热金属熔池,实现了传感器静态定度;采用阶跃上升的高功率CO2激光脉冲对黑体感温腔加热进行动态标定,解决了此类高温传感器在工程应用中的标定问题。实验结果表明该传感器响应时间在10^-2s数量级,标定技术简单实用,利用该传感器首次成功地测量了某导弹发射时的瞬态高温。     

露点温度传感器发展趋势综述

介绍了目前露点温度传感器领域的研究现状,阐述了光学式、谐振式、电学式、热学式、重量式、化学式露点温度传感器的原理及构造,指出光学式露点温度传感器测量精度极高,其中冷镜式露点仪可作为湿度计量标准;谐振式露点温度传感器具有体积小、成本低、响应时间短、灵敏度高、可靠性好的特点;电学式露点温度传感器灵敏度高、功耗小,便于实现小型化、集成化;重量法是准确度最高的湿度绝对测量方法;化学法常用来测量低湿环境下的有机混合气体。探讨了露点温度传感器在环境监测、工业制造、医疗诊断等领域的应用情况,指出未来露点温度传感器将会向高精度、高稳定性、高响应的方向发展,且应用范围将进一步拓展,以满足极端环境下的测量需求。     

Chemical sensors for portable, handheld field instruments

A review of three commonly used classes of chemical sensor technologies as applicable to implementation in portable, handheld field instruments is presented. Solid-state gas and chemical sensors have long been heralded as the solution to a wide variety of portable chemical sensing system applications. However, advances in optical sensing technology have reduced the size of supporting infrastructure to be competitive with their solid-state counterparts. Optical, solid-state, and hybrid arrays of sensors have application for portable instruments, but issues of insufficient selectivity and sensitivity continue to hamper the widespread introduction of these miniaturized sensors for solving chemical sensing problems in environments outside the laboratory. In this article, we evaluate three of the major classes of compact chemical sensors for portable applications: (solid-state) chemiresistors, (solid-state) CHEMFETs, and (optical) surface plasmon resonance sensors (SPR). These sensors are evaluated and reviewed, according to the current state of research, in terms of their ability to operate at low-power, small-size, and relatively low-cost in environments, with numerous interferents and variable ambient conditions     

低成本光散射颗粒物传感器性能影响因素综述

低成本光散射颗粒物传感器由于体积小、电力驱动要求低、能实时监测的性能,极大地降低了环境空气网格化监测的成本,具有巨大的应用前景。但该类颗粒物传感器在实际使用中,输出结果受到多方因素的影响。研究人员已对不同环境条件下、长期使用过程中以及在时空分布状态下监测数据的可靠性等方面进行了探索和研究。由于目前国内没有相关标准,因而检测参数、检测方法都缺乏统一性和可比性。针对低成本光散射颗粒物传感器性能特征影响因素研究进行综述,为该类传感器性能的提升以及计量评价体系的建立提供合理化建议。