ZO—14型数字氧量计“短偶保护”系统

为控制锅炉燃烧处于最佳状态,我厂采用ZO—14型数字氧量计测量炉中的含氧量.这种测氧仪器使用的一次元件是在恒温780℃的条件下工作的,为此,仪器采用可控硅自动温控电路,保证其正常工作.它的恒温过程是以热电偶作为感温元件,热偶信号与恒温设定信号比较以达到恒温控制.如果热电偶或补偿导线故障短路(由于现场条件恶劣,这种情况时有发生)将使热偶信号小于恒温设定信号,使一次元件始终处于升温状态,直至测氧探头被烧毁.为避免上述问题的发生,笔者设计了一     

热电偶的测温原理及误差分析

温度是一个重要的物理量,许多物理现象和化学性质都与温度有关,许多生产过程均在一定温度范围内进行,所以在国民经济各个领域中,必然会遇到有温度测量的问题。而热电偶具有结构简单,制造容易,测量方便等优点,在温度测量中得到广泛地应用。它基于物体的热电效应,将温度信号转换成电压信号进行传递,这种测温方式不仅可以远距离传递,而且能够集中检测和控制。但要得到正确的测量结果,必须认识热电偶的性能和使用方法,否则将会带来很大的误差。     

热电偶的接线问题

在材料的热处理(加工)过程中,常需要对温度进行准确的测量,以便对整个过程进行平稳地控制。尤其是实验条件下,对所测量的温度的准确度要求很高。在这些领域温度的测量通常采用热电偶传感器来实现。热电偶本身具有经济、测量误差小等优点。由于热电偶在测量中产生的电信号是毫伏级的,若在热电偶与测量设备的导线连接点上处理不当就会产生错误的测量结果。尤其在现场处理温度测量值困难,需要将不同的测量点的信号集中引到中心测量站来分析时,或在热处理过程中,需对几个测温点同时并行监测或模拟分析时,需要在热电偶回路中通过接点引线…     

热电偶参比端温度补偿方法

温度测量中,热电偶参比端温度一般不为０℃、必须对其补偿。该文介绍了４种补偿方法。恒温法包括冰浴法和恒温箱法,冰浴法简单易行,补偿精度高,特有知实验室,计量室和仪表生产厂校验热电偶：恒温箱法精度不高,但较方便。     

热电偶信号现场校验方法

热电偶信号现场校验方法浙江省电力试验研究所龚皓（３１００１４）大机组采用分布式控制系统（ＤＣＳ）之后，大量的热电偶温度信号都通过热电偶测量卡件进入ＤＣＳ系统，这些热电偶测量卡件需要定期检查和校验。由于热电偶信号数量很大，使得仪控人员在调试和日常维护期...     

微机控制的热电偶自动检测装置

微机控制的热电偶自动检测装置,主要用于检测热电偶,它可以控制三个测试炉,设定13个温度点,对八种类型的60支热电偶同时进行自动检测。并且能在检定温度点上、下10℃内对热电偶之热电势作准线化圆整计算,输出打印表格。由于配有IEEE 488接口,可以方便地与各种仪表连接。本装置在用户通过键盘输入被测热电偶类型,检定温度点之后,整个检测过程包括升温、恒温、数据采集、数据处理、打印制表都是自动化的。     

测温元件选型对火电机组温度测量精确度的影响分析

大型火电机组温度信号的准确测量,对机组的安全、经济运行起着至关重要的作用。热电偶、补偿导线及热电阻的正确选型是保证温度测量准确性的关键。文章针对火电机组在热电偶、补偿导线及热电阻的选型和使用中遇到的常见问题进行了分析,具有较强的指导意义。     

用热电阻端电压进行热电偶自由端温度自动补偿

热电偶温度计长期以来广泛地应用于工农业生产和科研中。但是,热电偶测温在不附加其他装置的情况下,所得到的温度值仅是热电偶两端的温差值。为了得到测点的实际温度值,就必须将热电偶的自由端放入已知温源内作基准温度,然后将仪表所显示的数值再加上基准温度值。这个基准温度,过去通常用一已知的恒温源。这个方法可以得到较高的测量精度,但用起来极不方便,特别是携带使用很困难。本文介绍一种用热电阻端电压通过运算放     

MAX6675在各种型号热电偶温度测量中应用

文中介绍MAX6675 K型热电偶信号放大与数字转换器的基本原理.并介绍软件实现MAX6675在与K型热电偶特性相近的其它型号,热电偶温度测量中应用的方法.     

单片机在热电偶模拟器中的应用

概述热电偶是测温传感器之一，尤其在温度高的场合，其特点是输出电压随温度的变化而变化。通过测量热电偶的输出电压便可以测出现场的温度，再通过二次表便可直接读出温度值。本文介绍的热电偶模拟器是为标准二次仪表而研制的，它可以模拟B、E、K、S、T五种热电偶，同时还可提供0～SV和0～20mA标准信号输出。可对二次仪表进行校准。1硬件本模拟器硬件包括8031单片机、最小系统键盘显示电路、12位D／A转换器、16位A／D转换器和信号处理电路等几部分。图1是电路框图。本模拟器采用闭环调节方式，单片机8031通过D／A转换器和mA信号放大…     

A Multiagent-Based Dispatching Scheme for Distributed Generators for Voltage Support on Distribution Feeders

This paper illustrates how a multiagent system (MAS)-based scheme can be developed for a control/optimization problem. The prototype problem considered is the dispatching of distributed generators on a distribution feeder to provide voltage support. The popular control net protocol (CNP) for MAS has been adopted to facilitate distributed control. This paper illustrates that characterization of the optimal solution is necessary in order to develop a protocol for the MAS to implement. This paper also shows that MAS facilitates a model-free control procedure, as it can monitor the local sensitivities. Test results, based on simulations on a prototype feeder, show that the proposed MAS-based control scheme is very effective in obtaining the solution for the prototype problem. The proposed method needs fast communication among the distributed generators (DGs) in order to assure fast response during emergency conditions. Communication requirements have also been identified in this paper     

新型磁控开关型故障限流器拓扑及试验研究

基于饱和铁心型高温超导故障限流器的拓扑,提出了一种适用于中高压电网的磁控开关型故障限流器拓扑结构,在偏置回路中串联了一个限流电感,通过故障前后交流电流的变化自动实现限流电感的退出和接入,从而实现对短路电流的限制,并研制了一台220 V/50 A试验样机。对限流器样机的试验结果表明,磁控开关型故障限流器在正常工作时电压损耗很小,对线路几乎没有影响;故障发生后,限流电感立即自动插入故障回路进行限流,基本不产生谐波,运行控制灵活且简单可靠,对短路电流具有快速、有效的限制作用。     

A compact integrated visual motion sensor for ITS applications

We have developed a prototype of a compact integrated visual sensor which detects direction and velocity of motion on a focal plane in a wide brightness range in real time with a newly devised motion measurement method. The sensor is composed of a lens and a single-chip very large scale integration whose die size is 2 mm /spl times/ 2 mm that was fabricated with a 1.5-/spl mu/ standard CMOS process. The spatial resolution is 10 /spl times/ 2. As a result of performance evaluation of the prototype sensor, it was confirmed that the sensor can detect motion direction and velocity up to an on-chip image velocity of 100 mm/s in a response time of 10 /spl mu/s under an illuminance range between 100 and 100,000 lux. Furthermore, we have demonstrated effectiveness of the visual sensor by applying the sensor to running vehicle detection on a road and blind-corner monitoring at a road junction.     

Low- and zero-speed sensorless control of synchronous reluctancemotors

This paper presents a position sensorless vector control able to drive synchronous reluctance motors in any working condition, including low- and zero-speed operations. The proposed control scheme is based on calculating the rotor position from the measurement of an additional high-frequency stator current component and allows a low-cost implementation; moreover, it does not require the knowledge of any motor parameter, nor particular care for motor starting. Simulation and experimental results on a 1.5-kW prototype are presented to evaluate the consistency of the developed technique     

基于DSP+CPLD的双级矩阵变换器设计与实现

传统矩阵变换器的结构简单,功率密度较高,但其换流问题和复杂的PWM调制方法限制了它在工业领域中的应用.双级矩阵变换器(TMC)在保持传统矩阵变换器所有优点的同时,可使PWM调制算法更加简单.整流端的开关实现了零电流换流,没有传统矩阵变换器中的换流问题.针对TMC的控制要求,提出了一种基于DSP CPLD实现TMC的方法;开发了一套TMC装置.实验结果表明,该TMC具有优良的输入输出特性.     

dSPACE快速控制原型在电池管理系统中的应用

快速控制原型是一项控制领域的新技术,具有效率高、成本低等特点。文章以铅酸电池管理系统为例,重点介绍了电池管理系统的快速原型控制开发流程,用于检测串联电池组的信号调理电路,电池管理系统的控制策略,以及利用ControlDesk对电池管理系统中的参数进行在线调整。最后用半实物仿真的实验结果证明了控制策略的可行性。     

基于红外热成像的PCR温控系统

电化学实时定量PCR仪中,对热循环3个温度区试剂温度的精度控制至关重要,因为其决定了PCR反应效率.根据非稳态传热原理,热量从基座传递到试剂存在延迟,因此基座上的接触式温度传感器无法直接测得试剂的温度.设计基于红外热成像仪温度检测的温控系统.可以同时对多通道试剂表面的温度进行直接测量,从而准确控制DNA解链-结合-延伸时间,提高DNA扩增效率.为了实现红外热像仪对温度的精确测量,对获取的红外温度进行中值滤波,根据热辐射理论与红外热像仪的测温原理以及公式推导,在线得到被测试剂表面发射率,通过换算从而获得试剂真实温度.实验表明,校准后热像仪测温精度由2.0℃提高到0.3℃;对试剂表面温度的监控使得PCR温控更加准确高效,具有重要意义.     

提高电能表现场校验仪抵御温度干扰能力的技术

受高低温环境温度的影响,电能表现场校验仪的现场测量精度可能会显著下降,无法做出正确检定。通过对电能表现场校验仪的测量原理和硬件结构的深入分析,揭示了高低温环境对校验仪测量精度的影响机理,提出了一种基于关键元器件温漂系数综合优化的改进方案,并研制了样机。试验结果表明,在-30~55 ℃,样机均能够保持0.05S级准确度,平均温度系数不超过0.08/℃。     

Noninvasive measurement of instantaneous, radial artery blood pressure

A new prototype system for the noninvasive measurement of instantaneous blood pressure (BP) in the human radial artery has been developed. The system is based on the volume-compensation method, but several components were newly designed, namely, a disk-type cuff for local pressurization and a nozzle-flapper-type electro-pneumatic converter (EPC) for the cuff-pressure control. Results of experiments indicated that, using the disk-type cuff, the radial artery could be completely compressed, and the newly devised EPC had sufficient frequency response for BP measurement in humans. It was also found that the prototype system comprising these components was capable of noninvasively measuring instantaneous BP in the human radial artery, not only under rest conditions but also in a stressful condition, such as during the cold pressor test. In conclusion, the newly developed local pressurization technique appears promising as a useful and helpful means for instantaneous BP monitoring over longer periods of time than have previously been possible. Using this method, it is possible to construct an instrument that is more compact and more comfortable for the subject to use than a conventional commercial instrument. Finally, it has been reported that it may be possible to monitor cardiac output continuously by BP waveform analysis. Thus, continuous cardiac output monitoring might be another potential and important application of the newly designed instrument.     

嵌入式系统在热电厂流量积算仪中的应用

热力发电时实时监测水蒸汽的温度、压力和流量以便及时控制发电过程是非常重要的。运用嵌入式微控制器组成的流量积算仪可以及时检测生产过程中水蒸汽的温度、压力和流量，并积算流量，通过RS485通信接口将检测结果发送给远程控制中心。文中给出了流量测量、积算的方法，阐明了系统硬件设计与软件实现的技巧。实际应用表明，该流量积算仪性价比高、测量准确、运行可靠，具有较大的应用价值。