University of DebrecenFaculty of Engineering

Process Control

Mechanical Engineer BSc Education

Lecturer : Krisztián Deák

2015.1

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Introduction

Name: Krisztián DeákRoom: 307., Faculty of Engineering, University of DebrecenEmail: deak.krisztian@eng.unideb.huWeb: http://www.mk.unideb.hu/userdir/deak.krisztian/Phone: 06-52-415-155 / 77780

Introduction• Process control is an engineering discipline that deals with

architectures, mechanisms and algorithms for maintaining the output of a specific process within a desired range. For instance, the temperature of a chemical reactor may be controlled to maintain a consistent product output.

• Process control is extensively used in industry and enables mass production of consistent products from continuously operated processes such as oil refining, paper manufacturing, chemicals, power plants and many others. Process control enablesautomation, by which a small staff of operating personnel can operate a complex process from a central control room

• Process control is an engineering discipline that deals with architectures, mechanisms and algorithms for maintaining the output of a specific process within a desired range. For instance, the temperature of a chemical reactor may be controlled to maintain a consistent product output.

• Process control is extensively used in industry and enables mass production of consistent products from continuously operated processes such as oil refining, paper manufacturing, chemicals, power plants and many others. Process control enablesautomation, by which a small staff of operating personnel can operate a complex process from a central control room

Introduction• Process control is an engineering discipline that deals with

architectures, mechanisms and algorithms for maintaining the output of a specific process within a desired range. For instance, the temperature of a chemical reactor may be controlled to maintain a consistent product output.

• Process control is extensively used in industry and enables mass production of consistent products from continuously operated processes such as oil refining, paper manufacturing, chemicals, power plants and many others. Process control enablesautomation, by which a small staff of operating personnel can operate a complex process from a central control room

Introduction• Process control is an engineering discipline that deals with

architectures, mechanisms and algorithms for maintaining the output of a specific process within a desired range. For instance, the temperature of a chemical reactor may be controlled to maintain a consistent product output.

• Process control is extensively used in industry and enables mass production of consistent products from continuously operated processes such as oil refining, paper manufacturing, chemicals, power plants and many others. Process control enablesautomation, by which a small staff of operating personnel can operate a complex process from a central control room

Introduction• Process control is an engineering discipline that deals with

architectures, mechanisms and algorithms for maintaining the output of a specific process within a desired range. For instance, the temperature of a chemical reactor may be controlled to maintain a consistent product output.

• Process control is extensively used in industry and enables mass production of consistent products from continuously operated processes such as oil refining, paper manufacturing, chemicals, power plants and many others. Process control enablesautomation, by which a small staff of operating personnel can operate a complex process from a central control room

Types of Input Signals

• Static• Dynamic (Time dependence) - Steady periodic, complex periodic - Nonperiodic: nearly periodic or transient - Single pulse. - Random• Analog or digital: - Analog; continuous signal, - Digital; distinct values, step changes.

Calibration• Calibration involves the determination of the

relationship between the input and output of a measurement system

• Eliminate Bias error• The proving of a measurement system’s capability

to quantify the input accurately• Calibration is accomplished by applying known

magnitudes of the input and observing the measurement system output

Primary Standards For Comparison and Calibration

• SI System: Meter – Kg -- Sec.– Kelvin – volt - Mole – Ampere – Radian

• LENGTH (meter): Distance traveled by light in vacuum during 1/299792458 of a sec.

• MASS (Kg.): International prototype (alloy of platinum and iridium) kept near Paris.

• TIME (Sec.): Duration of 9192631770 periods of the radiation emitted between two excitation levels of Cesium-133

• TEMPERATURE (Kelvin): K = oC + 273

Uncertainty of Measurements

• Measurement error = Measured result - True value • The true value of a measurand is Unknown ( Error is

unknown )• The potential value of error can be estimated

(uncertainty)• Two types of error:- Systematic errors (bias) and Random errors ( Statistics to estimate random errors)

SOURCE OF ERRORS

Measurement errors

Bias and Random Errors

MEASUREMENT STAGES

• Data transmission – Gets data between measurement elements

– Wire, speedometer cable, satellite downlink system

• Data storage/playback – Stores data for later retrieval

– Hard drive, RAM

• Data presentation – Indicators, alarms, analog recording, digital recording

Periodic Wave and its Spectrum

Time Domain & Freq. Domain

frequency spectrum examples

Square and Hanning window functions

Shannon law

Periodic Signals

Sine Wave Digitising

Periodic Wave and its Spectrum

Square Wave and its Spectrum

Analog and Digital Signals

Analog RC Filtering

Measuring System Stages

Resolution of an A/D Converter

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Tachometer

A tachometer (revolution-counter, tach, rev-counter, RPM gauge) is an instrument measuring the rotation speed of a shaft or disk, as in a motor or other machine.[1] The device usually displays the revolutions per minute (RPM) on a calibrated analogue dial, but digital displays are increasingly common.

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Accelerometer

An accelerometer is a device that measures proper acceleration.

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Force gauge

A force gauge (also force gage) is a small measuring instrument used across all industries to measure the force during a push or pull test.

A digital force gauge is basically a handheld instrument that contains a load cell, electronic part, software and a display. A load cell is an electronic device that is used to convert a force into an electrical signal. Through a mechanical arrangement, the force being sensed deforms a strain gauge. The strain gauge converts the deformation (strain) to electrical signals. The software and electronics of the force gauge convert the voltage of the load cell into a force value that is displayed on the instrument.Test units of force measurements are most commonly newtons or pounds

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A load cell is a transducer that is used to convert a force into an electrical signal. This conversion is indirect and happens in two stages. Through a mechanical arrangement, the force being sensed deforms a strain gauge. The strain gauge measures the deformation (strain) as an electrical signal, because the strain changes the effective electrical resistance of the wire. A load cell usually consists of four strain gauges in a Wheatstone bridgeconfiguration. Load cells of one strain gauge (quarter bridge) or two strain gauges (half bridge) are also available.[1] The electrical signal output is typically in the order of a few millivolts and requires amplification by an instrumentation amplifier before it can be used. The output of the transducer can be scaled to calculate the force applied to the transducer. The various types of load cells that exist include Hydraulic load cells, Pneumatic load cells and Strain gauge load cells.

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Strain gauge

A strain gauge (also strain gage) is a device used to measure strain on an object. Invented by Edward E. Simmons and Arthur C. Ruge in 1938, the most common type of strain gauge consists of an insulating flexible backing which supports a metallic foil pattern. The gauge is attached to the object by a suitable adhesive, such ascyanoacrylate.[1] As the object is deformed, the foil is deformed, causing its electrical resistance to change. This resistance change, usually measured using a Wheatstone bridge, is related to the strain by the quantity known as the gauge factor.

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Strain Gage [Gage Factor = (∆R/R)/(∆L/L)

& Young’s Modulus = (P/A) / (∆L/L) ]

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Wheatstone Bridge

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