Part4 UNIT4 A Indicting Instruments.doc

UNIT4 A Indicting Instruments 指示仪表 General Introduction 总体介绍Generally an indicator consists of an assembly for producing and controlling (1) the motion of a pointer with relation to a stationary scale, or (2) the motion of a scale with realtion to a fixed point or line of reference, or (3) the presentation of data in digital form (numeric or alphanumeric). Within this fundamental framework there are scores of variations.通常一个指示器由一个集合组成，这个集合能产生和控制：（1）与一个固定范围相关的指针的运动，（2）与一个固定参考点或一根固定参考线相关的范围的变动，（3）用数字形式（数字的或字母数字混合的）表示数据。在这个基本的框架内有刻度的变化。Another classification would break indicating instruments down into three categories: (1) mechanical types of devices as for example, the familiar dial-type pressure gage or the rise or fall of a column of mercury in a thermometer or barometer, (2) optical types of designs wherein the moving pointer may be a weightless beam of radiation, as for example, a light-beam-type galvanometer or one of the many configurations of cathode-ray tube (CRT) and associated electronic display tube indicators, and (3) combinations of electromechanical, electrooptical, and even electrochemical principles.另一种分类法把指示仪器分为三类：（1）机械类设备，比如，熟悉的刻度盘式压力表或汞柱在温度计或气压表中升降，（2）光学设计类型，在仪器里运动指针可以是一个没有重量的放射束，例如，一个光束电流计或多种阴极射线管（CRT）和相关电子显示管指示器的一种，（3）电力机械、电光学和甚至电化学原理的组合类型。For convenience, indicators also may be classified as (1) analog indicators in which all or portion of a calibrated scale is in evidence so that the observer sees the indication in continuum so to speak-against all or part of the total range within which the indicator may swing, and (2) digital indicators in which information is indicated a piece at a time. In addition to precision digital-type indicators, alarms and annunicators also operate on a pseudodigital principle, in that they only indicate certain Go/No-Go types of situations as in the use of colored lights or horns and bells to indicate limits that have been exceeded.为方便起见，指示器也可以分为（1）模拟指示器，在其中全部或部分刻度很明显，因此观察者看到的显示是连续的，所以整个范围内的全部刻度或部分刻度内指针可能摆动的话会受到观察者抨击，（2）数字指示器，在任意时刻只能显示部分信息。除了精确数字式仪表外，警报器和信号器同样根据近似于数字式的原理工作，因为它们仅指示某些运行或停止的状态，就像使用彩灯、喇叭或电铃来指示某些超出界限的情况。There are several forms of indication, reasonably uncommon except for very specific purposes, which illustrate the ingenuity that instrument engineers have applied to data display problems. The pyrometric cone and colored crayons and paints which indicate (historically) whether or not a certain temperature range has been exceeded serve a real need in certain high-temperature measurement situations, particularly where motion, as in tunnels and kilns, is involved. Manually operated, color-matching optical pyrometers also present an unusual and interesting indicating format.有几种形式的指示器，相当少见，除了非常特殊的目的，它表明了仪器工程师把它应用于数据显示问题时的心灵手巧。测温锥、彩色粉笔和颜料可以表明温度在过去是否超越了某个范围，这在某些高温测量情况下是确实需要的，特别是在移动过程中，例如在隧道窑中涉及到。手动操作、彩色匹配的光学高温计也代表了一种不寻常和令人感兴趣的指示形式。Indicating instruments also can be classified in terms of speed which, unless associated with a rapid-recording means, must fall within the capabilities of human identification and resolution. Although these characteristics vary considerably from one human being to the next, the standard of 24 frames per second as projected by motion picture equipment is indicative of the human limitation in time sensing individual events. In selecting the most appropriate (including economic justification) indicating mechanism for an instrument, the designer must consider the overall response of the measuring equipment as well as the time related importance of the measured data and the operator/instrument interfaceand, in so doing, thus will not overengineer or underdesign the mode of indication.指示仪器也能根据速度归类，除了一些与快速记录相关的方法以外，所有的仪表，其速度必须在人的辨别力和分辨力以内。虽然分辨力从一个人到另一个变化很大，但标准的每秒24帧的运动图像投影设备指出了及时感知个体事件时人的局限性。在为一台仪器选择最合适（包括经济方面的原因）的指示机制时，设计者必须考虑测量设备的整体反应和与测量数据重要性相关的时间以及人机界面这样做，显示模式既不会过分复杂，也不会设计欠周。 Moveable-pointer Indicators 可动指针仪表Conventional fixed-scale movable-pointer indicators vary in appearance, form of scale, and the plane in which the indicating pointer moves. In all cases it is essential that the scale be graduated and mounted so as to minimize reading errors. To avoid parallax errors a precision indicating instrument, which usually is read at very close range, often employs a mirror mounted beneath the pointer and adjacent to the scale graduations. In another arrangement the graduated portion of the scale is raised to the level (nearly) of the pointer tip, thus enabling accurate readings from greater angles of observation. The index may be in the form of a thin edgewise strip, a hairline scratched on each side of a transparent member, or a sharp arrow-shaped tip. Illumination, external or internal, is extremely important. Indicators that are intended for distant reading present entirely different design criteria, but usually have fewer graduations and pointers with proportionately large tip areas.传统的固定刻度可动指针仪表在外观、刻度形式、和指示指针运动的平面均不同。在所有情况下都标上刻度并固定以便最小化读数错误是最基本的要求。为了避免视差错误，通常在很小的范围内读数的精确指示仪器，常常在指针下安装一面镜子并紧挨着分刻度。另一种设置方法是刻度的分刻度部分提升到（接近）针尖所在平面，因此能从更大的观察角度准确读数。指针可以是细细的扁条形、在透明物体两边刻出细线的细丝形或锋利的箭头形。说明一下，外部形或内部形，是极其重要的。打算远距离读取的指示器有完全不同的设计标准，但是通常有较少的分刻度和针尖区域比例较大的指针。Frequently, the scales are used with two indicating pointers. The first pointer can be used to indicate the value of a first variable. The second pointer may indicate the value of a secend variable, or it may function as a manually set index or reference spotter. All the forms essentially are purely mechanical in nature, and most are widely used. Some typical movable-pointer indicators include straight scale, arc scale and segmental scale types, the scales of which are either vertically or horizontally mounted.经常使用带有两个指示指针的刻度盘。第一个指针用来指示第一个变量的值。第二个指针可以指示第二个变量的值，或实现手工设置指针的功能或充当参考指针。基本上所有形式本身都是纯机械的，且大多数得到广泛应用。一些典型的可动指针式仪表包括直线刻度、弧线刻度和扇形刻度，它们的刻度盘设置成垂直或水平的。 Moveable-scale Indicators 动圈式仪表The two common forms of movable-scale fixed-pointer configurations are rotating-drum-type scale and rotating-dial-type scale. The rotating-dial-type scale indicator consists of a flat disk scale and a stationary index. In practice, the angle of rotation seldom exceeds with a maximum calibrated scale length of about 30 inches. While in the precision indicator, the scale is finely divided from 300 to 600 divisions in a 24-inch scale length. The stationary index generally is in the form of a sharp tip or hairline. The rotating-drum-type scale indicator consists of a drum scale and a stationary index as well. The angle of rotation, scale length, and graduations are similar to those of the rotating-dial-type sclae. Both rotating-drum and dial-type indicators, as a general rule, are servo-operated. Drum and dial-type indicators permit close observations for relatively precise readings. Another type of movable-scale indicator uses a two-color painted metal strip which is moved in a vertical plane and is often used in connection with liquid-level measurements, with the dividing line representing the top of the liquid.动圈式固定指针结构两种最普遍的形式是旋鼓式刻度和旋盘式刻度。旋盘式刻度仪表由平面刻度盘和静态指针组成。实际上，拥有大约30英寸长的最大标定刻度盘的旋转角度也很少超过。而在精密仪表中，24英寸长的刻度盘的刻度精细地分为300到600等份。静态指针一般是细尖或细丝形式。旋鼓式刻度仪表由鼓式刻度盘和静态指针组成。旋转角度、刻度长度和分刻度与旋盘式刻度类似。作为一般原则，旋鼓式和旋盘式仪表都是伺服操作。为了相对精确的读数，旋鼓式和旋盘式仪表都允许近距离读数。另一种动圈式仪表用涂成两种颜色的金属条，金属条可以在垂直面移动，常常用与液面测量，它带有的分界线代表液面顶端。There is a typical panel meter in which moving scale is optically projected. The operation is accomplished by mounting a scale of photographic film to the moving coil of a core magnet mechanism in place of the usual pointer. A lamp, lens system, and mirror project this moving scale onto a coated window. The optical system expands the scale ten times its original value and the portion to be read appears on both sides of a hairline on the coated window. This design automatically avoids problems of parallax in reading. Furthermore, although long-scale lengths are available in projection, a shortened deflection angle of the mechanism is permitted, allowing high sensitivity.有一种典型的仪表板，它的可动刻度盘是光学投影的。它的运行是通过把胶片刻度镶嵌到可动的磁核线圈机械装置上代替