手机版av在线_96精品国产aⅴ在线观看_中文字幕35页_国产亚洲成AV人片在线观黄桃_全黄性色大片_免费视频h

上海京度電子科技有限公司

工業在線儀器簡介

時間:2018-8-18閱讀:1049

Instrumentation is the science of automated measurement and control. Applications of this science abound in modern research, industry, and everyday living. From automobile engine control systems to home thermostats to aircraft autopilots to the manufacture of pharmaceutical drugs, automation surrounds us. This chapter explains some of the fundamental principles of industrial instrumentation.

The first step, naturally, is measurement. If we can’t measure something, it is really pointless to try to control it. This “something” usually takes one of the following forms in industry:

·       Fluid pressure

·       Fluid flow rate

·       The temperature of an object

·       Fluid volume stored in a vessel

·       Chemical concentration

·       Machine position, motion, or acceleration

·       Physical dimension(s) of an object

·       Count (inventory) of objects

·       Electrical voltage, current, or resistance

·       Refractive Index

Once we measure the quantity we are interested in, we usually transmit a signal representing this quantity to an indicating or computing device where either human or automated action then takes place. If the controlling action is automated, the computer sends a signal to a final controlling device which then influences the quantity being measured.

This final control device usually takes one of the following forms:

·       Control valve (for throttling the flow rate of a fluid)

·       Electric motor

·       Electric heater

Both the measurement device and the final control device connect to some physical system which we call the process. To show this as a general block diagram

The common home thermostat is an example of a measurement and control system, with the home’s internal air temperature being the “process” under control. In this example, the thermostat usually serves two functions: sensing and control, while the home’s heater adds heat to the home to increase temperature, and/or the home’s air conditioner extracts heat from the home to decrease temperature. The job of this control system is to maintain air temperature at some comfortable level, with the heater or air conditioner taking action to correct temperature if it strays too far from the desired value (called the setpoint).

Industrial measurement and control systems have their own unique terms and standards. Here are some common instrumentation terms and their definitions:

Process: The physical system we are attempting to control or measure. Examples: water filtration system, molten metal casting system, steam boiler, oil refinery unit, power generation unit.

Process Variable, or PV: The specific quantity we are measuring in a process. Examples: pressure, level, temperature, flow, electrical conductivity, pH, position, speed, vibration.

Setpoint, or SP: The value at which we desire the process variable to be maintained at. In other words, the “target” value for the process variable.

Primary Sensing Element, or PSE: A device directly sensing the process variable and translating that sensed quantity into an analog representation (electrical voltage, current, resistance; mechanical force, motion, etc.). Examples: thermocouple, thermistor, bourdon tube, microphone, potentiometer, electrochemical cell, accelerometer.

ransducer: A device converting one standardized instrumentation signal into another standardized

instrumentation signal, and/or performing some sort of processing on that signal. Often referred to as a converter and sometimes as a “relay.” Examples: I/P converter (converts 4- 20 mA electric signal into 3-15 PSI pneumatic signal), P/I converter (converts 3-15 PSI pneumatic signal into 4-20 mA electric signal), square-root extractor (calculates the square root of the input signal).
Note: in general science parlance, a “transducer” is any device converting one form of energy into another, such as a microphone or a thermocouple. In industrial instrumentation, however, we generally use “primary sensing element” to describe this concept and reserve the word “transducer” to specifically refer to a conversion device for standardized instrumentation signals.

Transmitter: A device translating the signal produced by a primary sensing element (PSE) into a standardized instrumentation signal such as 3-15 PSI air pressure, 4-20 mA DC electric current, Fieldbus digital signal packet, etc., which may then be conveyed to an indicating device, a controlling device, or both.

Lower- and Upper-range values, abbreviated LRV and URV, respectively: the values of process oC and its URV would be 500 oC.
measurement deemed to be 0% and of a transmitter’s calibrated range. For example, if a temperature transmitter is calibrated to measure a range of temperature starting at 300 degrees Celsius and ending at 500 degrees Celsius, its LRV would be 300

Zero and Span: alternative descriptions to LRV and URV for the 0% and points of an instrument’s calibrated range. “Zero” refers to the beginning-point of an instrument’s range (equivalent to LRV), while “span” refers to the width of its range (URV − LRV). For example, if a temperature transmitter is calibrated to measure a range of temperature starting at 300 degrees Celsius and ending at 500 degrees Celsius, its zero would be 300 oC and its span would be 200 oC.



Controller: A device receiving a process variable (PV) signal from a primary sensing element (PSE) or transmitter, comparing that signal to the desired value (called the setpoint) for that process variable, and calculating an appropriate output signal value to be sent to a final control element (FCE) such as an electric motor or control valve.

Final Control Element, or FCE: A device receiving the signal output by a controller to directly influence the process. Examples: variable-speed electric motor, control valve, electric heater.

Manipulated Variable, or MV: The quantity in a process we adjust or otherwise manipulate in order to influence the process variable (PV). Also used to describe the output signal generated by a controller; i.e. the signal commanding (“manipulating”) the final control element to influence the process.

會員登錄

X

請輸入賬號

請輸入密碼

=

請輸驗證碼

收藏該商鋪

X
該信息已收藏!
標簽:
保存成功

(空格分隔,最多3個,單個標簽最多10個字符)

常用:

提示

X
您的留言已提交成功!我們將在第一時間回復您~

以上信息由企業自行提供,信息內容的真實性、準確性和合法性由相關企業負責,儀表網對此不承擔任何保證責任。

溫馨提示:為規避購買風險,建議您在購買產品前務必確認供應商資質及產品質量。

在線留言
主站蜘蛛池模板: 看av免费毛片手机播放 | 2023国产亚洲精品色爽无码 | 国产JIZZ中国JIZZ免费看 | 人人鲁免费播放视频 | 国产欧美亚洲精品第一区软件 | 精品国产伦一区二区三区 | 欧洲一区二区在线 | 人妻无码中文字幕永久在线 | 藏精阁成人免费观看在线视频 | 日本黄页网站免费观看 | 黄色在线视频观看 | 视频免费一区 | 亚洲欧美日韩一区二区在线观看 | 国产成人愉拍精品 | 国产精品日韩AV在线播放 | 久久精品视频大全 | 亚洲成人免费视频在线 | 超碰97精品 | 日韩精品一区二区三区免费观看 | www.久久国产精品 | 色yeye免费人成网站在线观看 | 超碰偷拍| 亚洲欧美日韩专区 | 国产成人啪精品视频免费网站 | 秋霞无码一区二区视频在线观看 | 久久久国产精品 | аⅴ资源天堂资源库 | 亚洲综合热 | 亚洲精品7777| 精品国产乱码久久久久久密桃99 | 久久九九国产精品 | 欧洲日本 | 国产精品高清乱码在线观看 | 久草视频免费观 | 日本老熟妇maturebbw | 亚洲国产成人久久综合人 | 国产熟女一区二区三区四区五区 | 一级片免费在线看 | av免费在线播放网址 | 亚洲精品资源 | 永久免费黄色 |