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.     

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.     

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.     

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.     

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.     

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。     

采用单片式探测器实现辐射通量定标

在基于双单色仪的辐射通量定标中,为了克服陷阱探测器视场小、孔径小的缺点,提出了采用单片式探测器替代陷阱探测器进行辐射通量定标的方法。采用只与光路垂直的一片硅探测器,使其光敏面与孔径光阑几乎重合,以增大探测器的孔径角。同时为了保证测量精度,采用偏置电流极低的运算放大器OPA128,并且增大了反馈电阻,以增强对弱信号的响应。采用单片式探测器对400—1000nm波长范围内进行辐射通量定标,系统不确定度包括：探测器响应拟合不确定度7‰,从陷阱探测器到单片探测器的传递不确定度3．14‰,光源波动小于1‰,系统重复性的不确定度3‰,最终合成不确定度为8．3‰,测量结果满足要求。     

真空热处理使用的新型温度传感器

简述了钨铼热电偶及复合管型铠装热电偶的性能及特点，着重讨论了渗碳炉，铜、铝等液态金属熔体温度检测技术，研制出真空炉，渗碳炉专用实体热电偶，铜水，铝液及高温盐浴炉连续测温用热电偶，成功地用于易普森工业炉，“一汽”，“二汽”、瓦房店轴承集团，贵州铝厂等在线温度检测，实践结果表明，热处理用温度传感器不仅能国产化，还可以进入国际市场。     

On the problem of gradient calibration in diffusion weighted imaging

A calibration method for diffusion‐weighted imaging using an isotropic phantom is proposed. The key point of the method consists in finding optimized balancing times for different orientations of diffusion‐encoding gradients followed by retrospective rescaling of the diffusion‐weighted images. The correction protocol was applied to produce improved fractional anisotropy maps which were analyzed with statistical histograms. The results demonstrate that the described scheme of systematic error reduction is a valid approach for quality control studies of gradient system performance for diffusion‐weighted imaging. © 2011 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 21, 271–279, 2011;