Using anisotropic heat flux sensors in aerodynamic experiments

We present the results of comparative measurements of the heat flux to a flat plate in a supersonic flow at a Mach number of M = 6, which were performed using the two following anisotropic heat sensors with different thicknesses of sensor elements: (i) Atomic Layer Thermo Pile (ALTP, Fortech GmbH, Germany) with a thickness of ～0.5 × 10^?6 m and (ii) gradient heat flux sensor (GHFS, St. Petersburg State Polytechnic University, Russia) with a thickness of ～2 × 10^?4 m. The ALTP sensor can be used for directly measuring heat fluxes in processes with a characteristic time above 10^?6 s. A method for mathematically processing the GHFS response signal is proposed that allows heat flux oscillations to be revealed in gasdynamic process with a characteristic time on the order of 10^?4 s.     

Gradient-type sensors for heat flux measurements high temperatures

New gradient-type heat flux sensors (GHFSs) are created, the thermal stability of which is increased due to the use of refractory metals and alloys forming a heterogeneous layered macrostructure. The new GHFSs allow the heat flux measurements to be performed at temperatures up to 1300 K.     

A radiation-convective method and equipment for checking heat flux sensors based on an adiabatic radiator

The results of the development and investigations of heat-measuring equipment which employs the radiation-convective method to check contact heat-flux sensors are presented.     

电视图像传感器检测平台的研制

为了准确、客观评价面阵CCD器件和整机多项性能参数,研制了电视图像传感器试验检测平台系统.整套系统装置采用组合式的设计理念,由两部分构成,电视图像传感器性能参数测试系统测量噪声、响应度、饱和照度、阈照度、动态范围、系统信噪比(SNR)、信号传递函数(SiTF)、均匀性等,其测试系统误差为4.28%;电视图像传感器成像系统组件定标与试验检测系统测量系统调制传递函数(MTF)、系统畸变、视场角与焦距、系统分辨率、系统光学同轴度等,其系统误差为4.48%.     

New calibration technique for microwave moisture sensors

A new calibration technique was developed for implementation with microwave moisture sensors. The calibration permittivity function used for this purpose allows computation of moisture content in granular materials with significant differences in shape, dimensions, and composition, independent of bulk density and with temperature compensation. A 3D representation is used to plot the calibration permittivity function as it depends on temperature and moisture content in wheat and corn. For each material, data points form a plane surface. These planes have nearly the same coefficients, which can be utilized for the development of a “universal” calibration method for moisture sensing in natural and manufactured granular materials. Foundations of the method are discussed based on results obtained for wheat and corn over a wide temperature range and at moisture contents of practical interest     

Linearization of calibration characteristics of capacitance pressure sensors

The nonlinearity of the calibration characteristics of capacitance pressure sensors and the approximation of these characteristics by means of various analytic functions are considered. The resulting approximation errors are estimated. A method and algorithm for digital linearization of the calibration characteristic of a sensor with the use of a cubic spline are proposed.     

Optoacoustic methods for frequency calibration of ultrasonic sensors

The frequency response of ultrasonic detectors is commonly calibrated by finding their sensitivity to incident plane waves at discrete frequencies. For certain applications, such as the emerging field of optoacoustic tomography, it is the response to point sources emitting broadband spectra that needs to be found instead. Although these two distinct sensitivity characteristics are interchangeable in the case of a flat detector and a point source at infinity, it is not the case for detectors with size considerably larger than the acoustic wavelength of interest or those having a focused aperture. Such geometries, which are common in optoacoustics, require direct calibration of the acoustic detector using a point source placed in the relevant position. In this paper, we report on novel cross-validating optoacoustic methods for measuring the frequency response of wideband acoustic sensors. The approach developed does not require pre-calibrated hydrophones and therefore can be readily adopted in any existing optoacoustic measurement configuration. The methods are successfully confirmed experimentally by measuring the frequency response of a common piezoelectric detector having a cylindrically focused shape.     

Measurement of transient heat flux using heat gauges

This paper describes the theoretical basis, the design, and the method of calibrating heat gauges for measuring variable heat fluxes.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 29, No. 5, pp. 814–820, November, 1975.     

车用压力传感器自动化校准系统的设计

设计了一套基于虚拟仪器(LABVIEW)的车用压力传感器自动化校准系统.该系统采用模糊参数自整定PID控制器和高低温箱,分别实现系统压力和温度的自动化精确控制,上位机通过RS232接口与高低温箱的控制器进行通信.实验结果表明,校准后的传感器的输出误差在0.1%以内,系统精度较高.系统的各项技术参数均能够满足汽车工业中大批量生产压力传感器的情形.     

Mass transfer and gas-phase calibration of implanted oxygen sensors

A protocol is described for validation of implanted oxygen sensors, in which sensors are calibrated in the gas phase where concentration boundary layers are absent. Calibration prior to sensor implantation and confirmation after sensor explantation allows separation of tissue mass transfer effects from sensor variance and drift. A model is given here that describes the oxygen-dependent signal current in terms of oxygen mass transfer to the sensor, permeability of the sensor membrane, and electrode area. The parameter used in the model to describe mass transfer to implanted sensors is consistent with experimental observations and allows comparisons with nonimplanted sensors. This method provides a bridge between the complementary approaches of empirical calibration and model-based calculation for determining oxygen concentration from the sensor response.     

Dependence of unsteady heat transfer on heat flux density

With the aid of an interferometer, the dependence of heat transfer coefficient in unsteady heat transfer on the rate of change of thermal stress at the heat transfer surface has been determined.     

Bi-layer functionally gradient thick film semiconducting methane sensors

Gas sensors based on metal oxide semiconductors like tin dioxide are widely used for the detection of toxic and combustible gases like carbon monoxide, methane and LPG. One of the problems of such sensors is their lack of sensitivity, which to some extent, can be circumvented by using different catalysts. However, highly reactive volatile organic compounds (VOC) coming from different industrial and domestic products (e.g. paints, lacquers, varnishes etc) can play havoc on such sensors and can give rise to false alarms. Any attempt to adsorb such VOCs (e.g. by using activated charcoal) results in sorption of the detecting gases (e.g. methane) too. To get round the problem, bi-layer sensors have been developed. Such tin oxide based functionally gradient bi-layer sensors have different compositions at the top and bottom layers. Here, instead of adsorbing the VOCs, they are allowed to interact and are consumed on the top layer of the sensors and a combustible gas like methane being less reactive, penetrates the top layer and interacts with the bottom layer. By modifying the chemical compositions of the top and bottom layers and by designing the electrode-lead wire arrangement properly, the top layer can be kept electrically shunted from the bottom layer and the electrical signal generated at the bottom layer from the combustible gas is collected. Such functionally gradient sensors, being very reliable, can find applications in domestic, industrial and strategic sectors.     

一种运用倾角传感器的阵形修正算法

垂直水听器阵在实际海洋环境中通常呈现出一定的倾斜状态,各阵元之间存在水平相对位移,对其性能带来很大影响.为了消除阵倾斜带来的影响,提出了一种运用倾角传感器进行阵形修正的算法.具体实现步骤为,首先用多个倾角传感器测得垂直阵上不同位置的倾角,然后通过求解线性方程组以及傅里叶级数分解的方法,利用倾角数据拟合出阵形的函数曲线,...     

Nonsteady method of determining heat flux

A method is described for determining intense heat flux, based on solution of the linearized heat-conduction equations. The data obtained are compared with data determined by the steady calorimeter method and the quasisteady method.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 30, No. 4, pp. 700–704, April, 1976.     

激光量块干涉测量中传感器的应用和校准

本文介绍了双波长激光量块干涉仪中使用的温度、湿度和气压传感器,描述了其工作原理、设计方案、测量不确定度以及校准方法。这些传感器同样可用于其他高准确度长度测量的激光干涉系统中。     

An inverse heat conduction problem with heat flux measurements

Using heat flux measurements as additional information to solve inverse heat conduction problems was and is still rarely employed. Lot of disadvantages linked to heat flux measurement specificities (local disturbance, intrusive measurement, lack of knowledge and proficiency, etc.) make people prefer temperature measurements which are well documented and very widespread. Solving inverse heat conduction problems with heat flux measurements is quite different than the one which uses temperatures and need to be investigated deeply. In this work, this problem is approached through the solution of a bioengineering problem consisting in the development of a non‐invasive blood perfusion probe. The effort here is focused on the development of a methodology for the estimation of time‐dependent blood perfusion from heat flux measurements. The physical probe incorporates a thin heat flux sensor, which is placed in contact with the tissue region where the perfusion is to be measured. The sensor records the heat flux due to an imposed thermal event, which is achieved by air flow. A one‐dimensional mathematical model is used to simulate the thermal event occurring at the contact region holding between the probe and the tissue. A combined parameter and function estimation procedure is developed to estimate simultaneously time‐dependent blood perfusion and thermal contact conductance between the probe and the tissue. The robustness of the method was demonstrated through several test cases using simulated data. The presented examples include various functional changes in the time evolution of blood perfusion. Results from this study have shown the feasibility of solving inverse problems with heat flux measurements and the two unknowns are estimated with no a priori information about their functional forms. Copyright © 2006 John Wiley & Sons, Ltd.