基于LabVIEW的热电偶数字化实时补偿

针对传统热电偶非线性和冷端温度补偿方法的不足,将虚拟仪器与传统测量技术相结合,设计了基于LabVIEW的热电偶数字化补偿软件。通过测量冷端温度,采用中间温度定律和二次查表法,实现了热电偶的非线性和冷端温度的高精度实时补偿。实验结果表明,软件具有良好的人机界面、易于操作,计算准确、效率较高,可以满足工业测试的需要。     

高精度标准测力仪动态温度补偿研究

温度补偿是研制高精度标准测力仪的难点与热点之一。本文提出了一种新的温度补偿方法,通过在标准测力仪弹性体上加贴热敏电阻,测量得到标准测力仪在不同温度下各检定点的试验力示值,同时利用多项式方程拟合出力值随温度变化曲线。利用该曲线,对不同温度条件下标准测力仪所测力值进行实时修正。实验结果表明,该方法不仅可以对标准测力仪进行实时温度补偿,而且可补偿的温度范围广,精度高。温度补偿后,保证标准测力仪在温度(+5~+35)℃范围内可达到0.02级精度要求。     

液体压力计温度补偿的讨论

文章介绍了一种基于温度补偿的超声测距液体压力计,包括U型管、超声测量系统、温度补偿系统和计算终端。通过理论推导建立液体压力计压力值与其影响量的数学关系式,温度实时补偿使测量结果的误差减小,提高了液体压力计的准确度。     

光扭矩传感器信号转换误差分析

光扭矩传感器的输出信号在进行光电转换过程中，由于温度影响，造成了直流电平漂移误差，影响系统的测量精度。对直流电平漂移误差进行了分析，针对产生误差的原因提出了采用正负温度补偿、热敏电阻和差动电路三种补偿方案，并进行了比较。实验结果表明，采用差动补偿电路的方法，效果良好，能有效地消除直流电平漂移误差。     

基于光纤光栅的扭矩测量系统设计

提出一种新的基于光纤光栅(FBG)技术的扭矩测量方法.分析了光纤光栅的传感机理,推导了扭矩与中心波长之间的数学关系,建立了双光纤光栅扭矩测量的理论模型.搭建实验平台,采用曲线拟合算法,对实测数据进行分析和处理,该扭矩测量系统的灵敏度达到22.89 pm/(N·m),最大非线性误差为0.23% FS,符合测量系统的误差要求,验证了此种扭矩测量方法的可行性.对温度补偿实验数据的分析表明:半桥式光纤光栅测量方案具有良好的温度补偿特性,能够补偿温度变化引入的测量误差,从而提高测量精度.     

基于LabVIEW的温度测量系统设计

设计一个基于虚拟仪器技术的温度测量系统,采用上下位机的结构,软件开发分别采用LabVIEW和汇编语言。详细介绍温度检测、放大、A/D转换等电路的设计,通过对热电偶的非线性进行补偿,实现电阻炉温度的较精确测量,利用LabVIEW的强大功能对温度数据进行实时处理和显示。该系统有很强的实用价值。     

热电偶智能测温方法的研究

本文介绍了直接在热电偶参考端加装温度传感器进行温度跟随测量,利用微计算机实现工作端和参考端温度信息的实时数据采集并通过软件进行参考端补偿和非线性处理的智能测量方案。采用此方案制成的ZWC-Ⅲ型智能高温测量仪可将测量准确度控制在千分之二以下。     

厚膜力传感器的─体化补偿

对以陶瓷双孔梁为弹性体的新型厚膜力传感器进行了零点温度漂移和零点的─体化补偿。分析了零点温度漂移和零点的补偿方法，在同一陶瓷弹性体上印刷、烧结、制备了厚膜力敏电阻，补偿厚膜热敏电阻及零点补偿厚膜电阻，并较好地是实现了零点温度漂移和零点的补偿。还探讨了补偿用热敏电阻浆料性能的改进。     

厚膜力传感器的一体化补偿

对以陶瓷双孔梁为弹性体的新型厚膜力传感器进行了零点温度漂移和零点的一体化补偿，分析了零点温度漂移和零点的补偿方法，在同一陶瓷弹性体上印刷，烧结，制备了厚膜力敏电阻，补偿厚膜热敏电阻零点补偿厚膜电阻，并较好地是实现了零点温度漂移和零点的补偿，还探讨了补偿用热敏电阻浆料性能的改进。     

薄膜热敏电阻

热敏电阻在晶体管电路的温度补偿,温度测量和控制或通讯机的自动增益调节等方面,早就获得了应用。热敏电阻主要是由过渡金属氧化物制成的半导体电阻器件,它们的特点是随着温度的升高,元件的电阻值显著减少。严格的说,这些元件应该叫做负温度系数NTC(Negative TemperatureCoefficient)热敏电阻,以区别于电阻值随温度上升而增加的钛酸钡系列的半导体陶瓷——正温度系数PTC(Positive Tempera-ture Coefficient)热敏电阻。     

点热源热脉冲法测算生物流体的热物性参数

采用微珠状热敏电阻作为点热源和测温元件，在一维点源脉冲传热模型的基础上建立一种同时测量生物流体热扩散系数、导热系数和热容的瞬态方法。运用非线性参数拟合，直接从感温热敏电阻对热脉冲温度响应中同时获取待测的热物性参数。实验中设计了一个高灵敏度的温度测量电路，测试结果表明，本方法测量误差小于4％。此外，还讨论了测量数据的处理和影响测量的因素。     

PTC热敏电阻在空分设备DCS系统中的应用

为实现对低温液体泵实行变频器和DCS系统的双重保护,将电机及其后轴承保护元件——PTC热敏电阻的阻值信号转换为干接点信号,接入DCS系统的DI通道。简介PTC热敏电阻的工作原理,介绍信号转换方案,分析热敏继电器的工作原理。     

Thermoanemometric transducer of pressure derivative

Conclusions The lower limit of the range of the transducer of p is given by the permissible reduction in the device sensitivity due to convection at low flow velocities while the upper limit is given by a reduction in the thermoanemometer sensitivity caused by an increased flow velocity. The static characteristic of the instrument is to a considerable extent nonlinear because of the nonlinearity of the thermoanemometer.The transducer time constant is the resultant of two components: of the time constant of the chamber and channel (pneumatic component) and the time constant of the thermoanemometer (thermal component). In the case of correctly selected chamber and channel components the time constant of the thermoaneommeter may be assumed to remain constant over the entire measurement range, being dependent only on the dynamic properties of the selected thermistor and on the coefficient of negative feedback in the system T=const. The time constant of the penumatic part of the instrument is determined by the upper and lower limits of the thermoanemometric device measuring p at the given sensitivity threshold of the thermoanemometer.The temperature and density errors of the transducer are large and necessitate the use of special compensating devices if the instrument is to be used over a wide temperature and pressure range.Translated from Izmeritel'naya Tekhnika, No. 1, pp. 45–48, January, 1973.     

A Log-Antilog Analog Control Circuit for Constant-Power Warm-Thermistor Sensors— Application to Plant Water Status Measurement

Warm-thermistor sensors are useful for making measurements of flow and the thermal properties of materials. This paper describes a log-antilog analog control circuit capable of monitoring a thermistor's internal temperature in both ambient temperature sensing mode and self-heating mode, while maintaining infinite precision, wide dynamic range and fast sensor response. A single self-referencing thermistor is used to avoid the problems associated with having to match a thermistor pair in order to obtain an over-temperature signal. Instead, thermistor power levels are switched over a range of 1:1000, allowing measurement of both ambient temperature and heated thermistor temperature during the rise and fall of the heat pulse by a single thermistor at the center of the heat field. This provides a sensitive measurement of the thermal diffusivity and advective properties of the surrounding medium. In this paper, such a sensor is used to investigate the thermal properties of a grapevine cane under conditions of irrigation stress.      

A digital anemometer

A digital anemometer has been developed for air flow measurements in home and office environments. The principle is based on hot-wire anemometry. The probe consists of a cold thermistor for flow temperature detection and a hot thermistor for flow rate detection. The latter is self-heated by a thermal bridge. Its unbalance voltage due to the air flow is compared with the reference response transformed into the time domain by direct digital synthesizing. This pulse-width modulation provides the linear digital representation of the flow rate under measurement. The unbalance component due to flow temperature is compensated by scaling the reference response depending on temperature detected by a cold thermistor. These linearization and compensation techniques make accurate measurements possible with a simple configuration. Performances of a prototype anemometer built using a one-chip 4-bit microcomputer are also presented to demonstrate the validity of these techniques     

Investigation the influences of geotextile on reducing the thermal reflective cracking using XFEM

Abstract

A 3D extended finite element model (XFEM) was constructed to investigate the thermal reflective cracking propagation and anti-cracking characteristic of geotextile. Influence factors of tensile modulus and placement location of geotextile were analysed. A temperature cycling test in the material test system was utilised in this work to validate the XFEM. Thermal simulations were performed considering the influences of solar radiation, air convection and air radiation. It has been found that crack initiated and propagated as temperature declining in earlier cycle, and crack length being fixed because of no more severe temperature variation based on maximum principal stress criterion. Geotextile with high tensile modulus had a significant influence on reducing the crack propagation compared with low tensile modulus geotextile or unreinforced situation. Geotextile placing at the bottom of asphalt surface had the best crack resistance influence, and geotextile placed at one-fourth depth from asphalt course bottom was more efficient than placed at other locations in terms of anti-crack propagation.     

金属反射型保温材料导热系数的测定

根据稳态法测量导热系数原理,设计了一套稳态导热系数测量装置,利用自动控制技术实现实验过程的可控性。通过与导热系数参比块的测量校对,该装置测量结果的准确度达到标准要求。并利用此测量装置对压力容器金属反射型保温层试样的导热系数进行了测定,测定温度在80～220 ℃范围内,测量误差小于1.3%,导热系数值由0.040 W/(m·K)变化到0.053W/(m·K)。     

透水沥青混合料的热物特性与热阻功能

为研究透水沥青混合料的热物性,基于热力学理论计算比较了透水沥青混合料和密级配沥青混合料的热导率、比热容、热扩散率等指标,并对透水沥青混合料的热物性指标与空隙率、含水率的关系展开分析;通过设计室内光照试验,测得相同的传热条件下两种材料表面和底部的温度变化。理论计算结果表明同密级配沥青混合料相比,透水沥青混合料的热导率降低约20%,热扩散率降低约10%;室内温度测试结果显示,透水沥青混合料试件表面较密级配沥青混合料试件温度低2～2.5℃,底部温度低3～3.5℃,说明透水沥青混合料具有热阻功能,对气温荷载变化的抵抗能力较强,验证了理论计算结果。     

Use of waste high density polyethylene as bitumen modifier in asphalt concrete mix

The purpose of this study is to investigate the possibility of using various plastic wastes containing High Density Polyethylene as polymer additives to asphalt concrete. It was investigated that the influence of HDPE-modified binder obtained by various mixing time, mixing temperature and HDPE content on the Marshall Stability, flow and Marshall Quotient (Stability to flow ratio). The binders used in Hot Mix Asphalt (HMA) were prepared by mixing the HDPE in 4–6% and 8% (by the weight of optimum bitumen content) and AC-20 at temperatures of 145–155 and 165 °C and 5–15 and 30 min of mixing time. HDPE-modified asphalt concrete results in a considerable increase in the Marshall Stability (strength) value and a Marshall Quotient value (resistance to deformation). Four percent HDPE, 165°C of mixing temperature and 30 min of mixing time were determined as optimum conditions for Marshall Stability, flow and Marshall Quotient (MQ). MQ increased 50% compared to control mix. It can be said that waste HDPE-modified bituminous binders provide better resistance against permanent deformations due to their high stability and high Marshall Quotient and it contributes to recirculation of plastic wastes as well as to protection of the environment.     

Method for specific heat measurement of thick film layers

A method of simple implementation is presented for the measurement of the specific heat of thick film layers. It has to do with a system, operating at room temperature in accordance with a dynamic non-adiabatic technique, whose function regards the transient phase of a heating process between two steady states. It consists of a compact ensemble of three elements: a small plate thermistor serving as a heater, an alumina disk as a sample support and a tiny calibrated thermistor as a temperature sensor. The voltage across the heater and temperature from the sensor are monitored. An accurate evaluation of the dissipated energy allows the absorbed energy, responsible for the temperature variation, to be brought out. That makes possible the determination of thermal capacity of a small mass material deposited on a substrate. The achievement of the result simply involves the recording of a voltage and temperature during the transient phase, a fitting procedure with given analytical functions and a mathematical elaboration. The measuring system, its calibration procedure together with the transient operation are described. An application concerning screenprinted ferroelectric thick films on alumina substrate is presented and the results discussed.