industrial control system czemplik

8/10/2019 Industrial Control System Czemplik

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IndustrialControl System

dr in. Anna Czemplik

(na prawach rkopisu)

Instrumentation of a technological process


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Industrial Control System (ICS) usually performs the following tasks:

1) an instrumentation of a technological process2) a data acquisition and a process control

3) a data transfer

4) human-machine interface (HMI)

These tasks correspond to the following subsystems of ICS:

I. measuring devices and actuators

II. field devices

III. a communication infrastructure

IV. supervisory computers (a complex system)


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The main topics:

I. Measurement devices

II. Actuating elements

III. Field devices - controllers

IV. Communication networks

V. SCADA & DCS

What is it? Definition

How does it work? Principle of operation

Main features

}

Instrumentation of a technological process

15 hours

} 15 hours


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Ia. Sensors Ia-1. Thermometers: a) Expansion thermometer; b) Pressure spring thermometer; c) Resistance thermometer; d) Thermoelectric thermometer;

e) Optical thermometer. Selection of thermometer and measuring circuit

Ia-2. Displacement and force sensors: a) Resistance displacement sensor; b) Piezoelectric displacement sensor; c) Piezomagneticdisplacement sensor; d) Inductive displacement sensor; e) Capacitive displacement sensor; f) Hall effect displacement sensor

Ia-3. Manometer: a) Hydrostatic manometer; b) Hydraulic manometer; c) Elastic manometer; d) Electronic manometer (strain gauge, inductive,

capacitive); e) Manometer with a force sensor. Selection of manometer

Ia-4. Level indicator: a) Water-level indicator; b) Float level gauge: c) Hydrostatic level gauge; d) Displacer level gauge; e) Ultrasonic level

gauge; f) Radar level gauge; h) Another l.g. (capacitive, eletrical, thermometer). Selection of level gauge

Ia-5 Flowmeter: a) Differential pressure flowmeter; b) Rotameter; c) Velocity-type flowmeter; d) Positive displacement flowmeter; e) Inductive

flowmeter; f) Ultrasonic flowmeter; g) Calorimetric flowmeter; h) Vortex flowmeter; i) Coriolis flowmeter; j) Open channel flowmeter. Selection of

flow meter Ia-6. Speed: a) Tachometer; b) Digital speed sensor

Ia-7. Relays: a) Non electrical relays; b) Electrical relays and switches

Ia-8. Physico-chemical properties: a) pH meter, ...

Ia. Sensor selection

Ib. Converters Ib-1. Measuring converters types and selection

Ib-3. Separating converters

Ib-4. Analog-to-digital converters

Ib-5. Digital-to-analog converters

Measuring devices; Instrumentation and control tag

II. Actuating elements

IIa. Final control element IIa-1. Valves

IIa-2. Pumps

IIb. Actuators IIb-1. Pneumatic actuator

IIb-3. Electric actuator - Electric motors: a) Brushed DC electric motor; b) Synchronous motor; c) Inductive motor

Electro-mechanical drive system


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control devices

plant

measurement

devices sensorsensin element

measuringconverter

actuating

equipmentfinal controlelement

actuator(actuating driver)

controller

A/D

converter

D/A

converter

communication system

supervisor system

Block diagram of a control system


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.

I. Measurement devicesa) Sensors

1 - temperature,2 - displacement,

3 - pressure,

4 - level,

5 - flow,

6 - rotational speed,7 - relays,

8 - electrochemical

b) Converters

1 - measuring,

2 - signaling,

3 - separating,

4 - A/D,

5 - D/A

c) Control engineering design

plant

sensorsensin element

measuringconverter

final controlelement


controller

A/Dconverter

D/Aconverter


supervisor system


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.

Sensor (transducer, measuring converter) - a device that converts a physical (chemical,

biological, ...) quantity into another signal (usually an electric signal). There are many

types of sensors base on different principles.

Measurement of a basic physical quantity:

1) temperature

2) displacement and force (also stress, strain)

3) pressure (also pressure difference)

4) level (also volume)

5) flow

6) rotational speed

More: http://www.omega.com/literature/transactions/

http://www.sensorland.com/

}force-related measurement

}amount-related measurement

and another:7) relays (two-stage transducer)

8) electrochemical transducer


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1.

liquid-in-glass mechanical

bi-metallic elongation-type

Principle: Thermal expansion of liquids or solid bodies

e.g. mercury-in-gas thermometeror alcohol thermometer

The difference in thermal expansion in the two metals

leads to a difference of lenght or to a twist of element

in proportion to the temperature

With increasing temperature,

the volume of liquid expands

and the meniscus moves up the capillary.


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1.

thermometricbulb

capillary

manometer(spring-type pressure gauge)

(gas thermometer)

Principle: The relation between temperature and pressure in a constant volume

The bulb is immersed in a heated substance.

The liquid (gas) expands causing the pressure spring to unwind.

Types:

liquid filled (mercury, ethyl alcohol, ...) gas filled (nitrogen, argon, helium)

vapor pressure (volatile liquid)


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1.

bifilar winding of metallic t.

PTC

Temperature dependence of resistance

NTC

platinum

R

T

metallic

thermistor (semiconductor)

NTC, PTC, CTC

ceramic

PTC

Pt 100, Ni 100 (i.e. 0C = 100 )

Principle: Temperature dependence of resistance

platinum

nickel

copper

Metal resistance increases under the influence of temperature


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1.

E=f(T1-T2)

T1 T2metal A

metal B

measuring junction

(hot junction)

connecting

head

1) Fe-konstantan2) NiCr Ni3) PtRh - Pt

500 1000 1500

2

1

E[mV]

C

3

(thermocouple, thermoelement)

Principle: Thermoelectric effect - if junctions of two different metal have a different

temperatures than a voltage is generated.

The construction of joint and shield


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1.

global radiation monochromatic

two-colour

(pyrometer)

Principle: Measurement of thermal radiation emitted by any matter with a temperature

greater than 0K

Measuring area

Non-contacting measurement

based on an optical system and a detector


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1.

0 C

expansion-200

500pressure spring -50 700

resistance -270 900

thermoelectric -100 1600optical 400

2700

1) Temperature range:

2) Contact or non-contact

(The main selection criteria)


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1.

Uz R0 Rw Rt

R1 R2

R3connecting wiring

Uz R0 Rw Rt

R1 R2

R3 connecting wiring

2-wire circuit

3-wire circuit

The connecting wiring

occur in

two legs of the bridge

The connecting wiring

are added to

the measured resistance


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R1 R2

Rt

Uz

R3

t0ehotjunction

mV

cold junction

e1

e2 e4

e3

mVt0

A

B A

C

Chot

junction

thermostat

cold junctions

1.

.

Circuit with the cold junction compensation

e=e1-e2 (e2=const), e3 = - e4

Simple circuit


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2.

Measurements of displacement (position) and force are similar on account of that the

displacement is a result of some force.

The force-related measurements contain a wide gamut of sensors for measuring:

stress (calculated by dividing the force applied by the unit area)

strain (defined as the deformation per unit length)

weight (the force on the object due to gravity)

acceleration (accompanied by a force)

torque (moment of force)

pressure (by definition the force per unit area)


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2.

l

R=rl

R=r

l

potentiometer

Principle: The resistance depends on the geometry of the resistor (and the resistivity of

the material)

linear

rotary

The linear or angular motion of a wiper

is converted into a changing resistance of potentiometer

strain gauge

The gauge is attached to the object by a suitableadhesive. As the object is deformed, the foil is deformed,

causing its electrical resistance to change.


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2.

Principle: Piezoelectric effect - some materials (e.g. quartz) generate a voltage under

influence of a mechanical stress.

In most cases, the same element can be used as:

piezo sensor that converts mechanical energy into electrical energy (it is referred to as "generators)

piezo actuators that converts electrical energy to mechanical energy (it is referred to as "motors)

[http://www.americanpiezo.com/knowledge-center/piezo-theory/piezoelectricity.html]

polarizationdisk compressed:

generated voltage

has the same polarity

as poling voltage

disk stretched:

generated voltage

has polarity opposite

that of poling voltage

applied voltage

has the same polarity

as poling voltage:

disk lengthens

applied voltage

has polarity opposite

that of poling voltage:

disk shortens


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2.

mAF

coil sensor

Principle: Mechanical strain has an influence on a magnetization of ferromagnetic

materials

transformer-type sensor

F

L

Measurement of inductance

Measurement of current in the secondary circuit

consisting of two push-pull winding(a differential measurement)


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2.

coil sensor

s

Ls0W2/

s

differential coil sensor

x

1

2

differential transformer-type sensor transformer-type sensor

x2

3U2

Principle: Displacement of a part of core involves changes in inductance

1) Measurement of inductance

2) Measurement of eddy current(eddy current linear encoder)

The primary winding are energised with a

constant amplitude A.C. supply. Thisproduces an alternating magnetic field in the

core and induces a signal into the secondary

winding (2,3) depending on the position of

the core.

The target is part of magnetic circuit


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2.

parallel-plate c.

x

x

differential parallel-plate c.

rotary c.

x

cylindrical c.

Principle: Displacement of a capacitor plate involves changes in capacity

x

Target

Sensor The target is one plate of the capacitor


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2.

x

N

SI+

-

UH

UH=kIB

Principle: Hall effect an electric current in the conductor placed in a magnetic field

causes a voltage difference (the Hall voltage)

The Hall voltage is developed between the two

edges of a current-carrying conductor whose faces

are perpendicular to an applied current flow.


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h

p1 p2

p1-p2=gh(1-2)

21

U-tube

p

float sensor

3.

(Hydrostatic pressure gauge)

Principle: Hydrostatic equilibrium between the pressure and the hydrostatic force per

unit area at the base of a column of fluid

(U-pipe)

Pipes and tubes are not the same

Pipe: The purpose with a pipe is the transport of a fluid like water, oil or similar, and the most import property is the capacity orthe inside

diameter.Tube: The nominal dimensions of tubes are based on the outside diameter. The inside diameter of a tube will depend on the thickness of the

tube. The thickness is often specified as a gauge.

The pressure is indicated by the difference in levels in

the two arms of the tube

The pressure causes a change of liquid

level and the float transfers it to an

indicator


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p

p1 p2

bell pressure gauge

p2p1

p2

p1

p1-p2=gh

p2

ring differential manometer

y

p

cy+mg=pA

piston pressure gauge

p

3.

(bell-type manometer)

(Hydraulic pressure gauge)Principle: Hydraulic equilibrium of the pressure and another force

(ring balance)The force of pressureis in balance with the spring

The balance the

force of pressure

and bouyant force


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Bourdon tube

p

diaphragm pressure gauge

p p

bellows pressure gauge

3.

(tube pressure gauge,spiral pressure gauge)

Sensor uses the deflectionof a flexible membrane

that separates regions of

different pressure

(Spring-type pressure gauge)Principle: Equilibrium of the pressure and a spring force

The curved tube is open to external

pressure input on one end and is

coupled mechanically to an indicatingneedle on the other end. The external

pressure is guided into the tube and

causes it to flex.

The bellows is stretched on

pressure influence


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capacitive

p

differential capacitive

p1p2

3.

Differential manometer withan elastic membrane is a

double capacitor

Principle: Conversion the pressure to a displacement or a mechanical stress and next an

electric measurement of this displacement.

inductive strain gauge

(measurement of inductance)

(measurement of resistance)

(measurement of capacity)

Displacement sensors and manometers

differ in a process connection


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3.

with piezoresistive

strain gauge

with piezoelectric sensor

with strain gauge

with strain gauge

Principle: Conversion the pressure to a force or a strain and next an electric

measurement this parameter.


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3.

1) Type of measured pressure

absolute pressure is zero-referenced against a perfect vacuum, so it is equal to

gauge pressure plus atmospheric pressure. gauge pressure is zero-referenced against ambient air pressure, so it is equal to

absolute pressure minus atmospheric pressure.

differential pressure is the difference in pressure between two points.

2) Compromise between an accuracy and susceptibility to overload3) Inertia measurement of slow/fast pressure changes

4) Process connection1 2A

h2-h1

h1h2

1 2

h2 h1

h2-h1

A

h2-h1 the pressure arisen from a liquid flowAssumption: no pipe resistance

p1=p2 p1>p2



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4.

glass level gauge

magnetic level indicator

Principle: Communicating vessels

It is perfect for high temperature and pressure

applications in case sight glasses and indicating

glass parts cannot be used for safety reasons

(tubular level gauge)


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4.

resistance

inductive

Principle: Liquid level float is buoyant in liquid and indicates the level

Float moves

on a linear resistor

Float causes a displacement

of a coil core


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4.

PP=p1-patm

patm

P=gh

h1

bell-type

P

capacitive

(Manometric level gauge)

Principle: The static pressure in the bottom is proportional to the liquid column in the tank

The pressure at a given depth in a static liquid

depends upon the density of the liquid and the

distance below the surface of the liquid

plus any pressure acting on the surface of the

liquid


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4.

(Buoyancy transmitter)

F

Principle: Archimedes' Principle - a body which is completely or partially submerged in

a fluid experiences an upward force (the buoyant force)

Sensor

in a side-and-bottom chamber

Sensor

without

chamber

Weighing of

the displacer element

Intelligent level transmitters based on

Archimedes buoyancy principle are

designed to measure liquid level,

interface and density.

Buoyant force moves a coil core

and changes its inductance


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4.

Example applications

Principle: Reflection of high frequency acoustic waves

The sensors emit waves (20 kHz to 200 kHz) that are reflectedback to and detected by the emitting transducer. The elapsed time

period between transmission and reception of the signal - at the

speed of sound - is measured and calculated as a distance and

computed into level or volume.

In order to improve the accuracy of

measurement it is important to take into

account a moisture, temperature, and

pressure changing speed of sound.


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4.

Principle: Reflection of microwaves

(Microwave sensor)

Speed of microwave is independent of moist,

vaporous, dusty, and temperature environments

The sensors emit waves (1 GHz to 30 GHz ) and measure the time

period between transmission and reception of the signal.


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4.

..

..

Principle: Property of sounder depends on its draught in liquid

Draught cools the measuring element, e.g. the resistance thermometer

Sounder is a superconductor and his resistance

depends on draught in a low temperature liquid

Sounder is a long capacitor and his capacity depends on draught


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4.

1) Type of medium (phase): liquid, solid or slurry

(the main selection criteria)

3) Conditions of measurement, e.g. temperature, pressure (or vacuum)

2) Properties of medium, e.g. dielectric constant, density


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5.

flow nozzle Venturi tube

orifice plate

p

(Orifice flowmeter)

Principle: Bernoullis principle an obstruction inserted in the flow causes a pressure

drop proportional to the square flow speed.

(Venturi meter)

Nozzle and tube offer advantages over orifice plates in that they require lessupstream piping and incur lower permanent pressure loss.

Pressure sensor measures the differential pressure before and within the constriction

5


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5.

plastic

glass

metal

Principle: Balance between the flowing force and the weight of the float

The rotameter consists of a vertically oriented glass (or plastic) tube with a larger

end at the top.The substance flows through the meter vertically from bottom to top and lifts the

float proportionally to the flow quantity.

5


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5.

screw f.

blade f.

turbine f.

impeller

counter

12 impeller

counter

Principle: The fluid flow actuates the movement of blades, screw or turbine-type impeller

proportionally to flow rate.

(Rotating meter)

The flow is calculated by

measuring and integrating

the flow speed over the

flow area


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5.

piston

four-wayvalve

Principle: Counting repeatedly the filling and discharging of known fixed volumes

A typical positive displacement flowmeter comprises a chamber that obstructs the

flow. Inside the chamber, a rotating/reciprocating mechanical unit is placed to

create fixed-volume discrete parcels from the passing fluid.

Piston is operated to fill a cylinder with the fluid

and then discharge the fluid. Each strokerepresents a finite measurement of the fluid

See also: http://www.efunda.com/designstandards/sensors/flowmeters/flowmeter_pd.cfm

5


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5.

electromagnet

electrode

(electromagnetive)

Principle: Faraday's law of electromagnetic induction - when a conductor moves through

a magnetic field then a voltage will be induced

The liquid serves as the conductor and the

magnetic field is created by energized coils

outside the flow tube. The inducted voltage isdetected with the aid of an electrode.

It can only be used for electrical conductive fluids as water.

5


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scheme

Z V

5.

Principle: Doppler effect - The frequency of the reflected signal is modified by the

velocity and direction of the fluid flow

(Ultrasonic Doppler flowmeter)

By measuring the frequency shift between the

ultrasonic frequency source, the receiver, and thefluid carrier, the relative motion are measured.

Doppler meters may be used where other meters don't work.

It can be installed outside the pipes (do not obstruct the flow )

It is sensitive to changes in density and temperature the fluid.

5


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5.

Principle: Intensity of cooling depend on the flow rate of the fluid

Two temperature sensors are in close contact with the fluid but thermal insulated from each

other. The flowing fluid cools both sensors but one of the two sensors is constantly heated.

The temperature difference between the two sensors is proportional to the flow rate.

5


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5.

Principle: Karman effect - an obstruction in a fluid flow creates vortices in a downstream

flow

Animation http://en.wikipedia.org/wiki/File:Vortex-street-animation.gif

Karman vortex street

Vortices cause a local disturbance of pressure

detected by the sensor. Frequency of vortices is

proportional to the flow rate

5


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Animation: http://www.emersonprocess.com/micromotion/tutor/42_densityoperatingprincipal.htm

5.

Principle: Coriolis effect -

It is a direct measurement mass (not sensitive to changes in pressure, temperature, viscosity and density )

The fluid runs through a U-shaped

tube that is caused to vibrate in an

angular harmonic oscillation. Due

to the Coriolis forces, an

additional vibration arise thatdeform the tube

5


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5.

Principle: An obstruction inserted in the flow causes a backwater

A common method of measuring flow through an open channel is to

measure the height of the liquid as it passes over an obstruction as aweir or flume in the channel.

Venturi flume V-notch weir

Common used obstruction types:

the sharp-crested weir,

the V-notch weir,

the Cipolletti weir, the rectangular-notch weir,

the Parshall flume

Venturi flume.

c

sharp-crested weir

5.


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1) If the flowrate information should be continuous or totalized?

5.


2) Type of medium: steam, gas, liquid

3) Properties of medium: viscosity (Reynolds number), density

4) Conditions of measurement, e.g. pressure, temperature

5) Unit

m3/s (volumetric flow rate, volume flow rate, rate of fluid flow, volume velocity) kg/s (mass flow rate)

6.


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Uzasil eg

dc generator

U1

eg1

ac generator

6.

Principle: A small ac/dc generator that develops an output voltage proportional to its rpm

(Rate generator)

The dc rate generator often has

permanent magnetic field excitation.

The rotor of the tachometer is mechanically connected, directly or indirectly, to the load .

The ac rate generator field is excited

by a constant ac supply

The phase or polarity of output voltage (eg) depends on the rotor's direction of rotation

6.


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6.

fn

fn

fzUz

N S

S N

Principle: A pulse generator plus a pulse counter

(rotational speedsensor)

(reed swich)

.


50/82

- vibrating fork liquid level switch (submergence, filling)

Principle: Overflow of a definite input value causes an abrupt change of output value

(usually closure of contacts used e.g. to direct control)

(Two-stage transducers)

Measurement sensors used to a detection of only two-stage.

liquid level switch, e.g.

pressure rise relay, e.g.

temperature rise relay, e.g.

- float switch (exceeding the level)

- bimetallic switch (overflow of temperature)

U-tube (mercury join contacts after the overflow of pressure)

acoustic

light-, ...- photodiode, photoresistor (proximity detector )

- microphone (detection of sound intensity, frequency)

.


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Principle: Relay - overflow of a definite input value causes a closure of contacts

reed switch

electrical activated device

close relation

N Sturn

N Stern

N S

tern

limit switch

Switch is operated by the motion of a machine part or presence of an object

.


52/82

a) pH pH meter

b) redox potential (oxidation/reduction potential, ORP) ORP meter

c) humidity hygrometer

d) oxygen (proportion of O2 in the gas or liquid ) oxygen meter, lambda sensor

e) conductivity conductometerf) suspension densitometer, suspension turbidity meter

g) water hardness

h) concentration refractometer

....

The main type of measurement:

.


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- concentration of hydrogen ions (H+)

- in practice from 10mol/l to 10-15 mol/l

pH

10-7 mol/l10010-14

14

7

0

H2O acidic solutionbasic solution

A typical pH probe consists of a

combination electrode, which combines

both the glass and reference electrodesinto one body. The probe produces a

small voltage (about 0.06 volt per pH

unit) that is measured and displayed as

pH units by the meter

Principle: The measurement bases on an electrode made of a doped glass membrane

that is sensitive to a specific ion

The ph meter requires a cleaning and a frequent calibration

because the glass electrode does not givea reproducible e.m.f. over longer periods of time

.


54/82

Requirements:

measurement value (temperature, pressure, ..)

range

accuracy class mounting of the instrument (process connection, location)

frequency response

environmental condition (e.g. Ex, dustiness, moisture)

operational reliability (e.g. periodical calibration)

dimensions, weight complexity of additional equipment

qualification of service staff (method of calibration or programming)

price of sensor and an additional apparatus

resolution of the measured signal

The main directions

Procedure of the sensor selection:

1) statement of the main requirements for sensor

2) review of available sensors from the point of view of fulfilment of requirements

.


55/82

Definition and classification

Classification of converters according to function:

1) measuring

conversion of a sensor signal into a standard signal

typical electric standard signals: 0-5mA, 0-10mA, 0-20mA, 4-20mA, 0-10V2) signaling

matching circut - exchange of one standard to another

current-current, voltage-voltage, current-voltage, voltage-current, current-

pressure (intersystem converter);

3) separating assurance of the galvanic isolation between functional sections of system

the same standard of input and output and the gain equal 1

4) analog-to-digital converter (ADC, A/D, A to D)

conversion a continuous quantity to a discrete time representation in digital form

typically the digital output is a twos complement binary number

5) digital-to-analog converter (DAC, D/A, D to A)

conversion of a digital (usually binary) code to an analog signal (current, voltage

or electric charge)

1.


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a sensor signal to the standard signal

According to input value:

converter of force, voltage, resistance, pressureAccording to principle of operation:

parametric, generating

According to construction (electric circuit)

open circuit (without a feedback)

close circuit (with a feedback)

According to modulation of output signal:

a) modulation of direct current levelb) frequency modulation

c) discrete output with modulation pulse-width (PWM)

1.


57/82

with modulation of direct current level

measuring converter of a resistance measuring converter of a small voltage

Rs

Rb

Rf

Us

Rr

Iout

Us

Rb

Rf

Us

Rr

Examples:

Rs resistance of sensor; Us voltage of sensor

Rb balancing resistance of the circuit; Rf feedback resistance; Rr receiver

1.


58/82

with frequency modulation

generating

tachometer generator

oscillatory with a free vibration

MC OS Cout

AC

in out

AF

l

string-type converter

(the force F into the frequency f)

ml

Ff

2

1=

Types:

position-type} modulating digital speed measurement

oscillatory with a forced vibration

MC matching,AC activation

OS - oscillatory system

Cout output converter

1.


59/82

with pulse-width modulation

LG C

Uout

UA

ULG

UX

UC

UA

UX

T

UULG

Uoutti

Example:

LG linear generator (g. of linear signal)

UA activation; C- comparator

Ux input voltage

Uout output voltage

1.


60/82

The main directions

Requirements:

a suitable static characteristic (linear or non-linear)

stability of characteristic

a small conversion error (e.g.


61/82

measuringconvertersensor

RA RBUR CB

Disturbing signals:

serial voltages

parallel voltages

galvanic separation

result of a inductive coupling between two wiresprimarily frequency of 50Hz and 100Hz

result of a ground loop

frequency of 50Hz5kHz,

high voltages, constant component

Suppression with the help of low-pass filter

passing the measured signal (frequency


62/82

xin=

= xout

GZ

M DTO

Iin

Iout

Application of galvanic separation

UP U I I I

UP UI

II

sys

I1

I21

2

100

200

200

200

200

3

4

5

6

Realization of galvanic separation

galvanic separation

transformer-type optoelectronic

4.


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A/D

Conversion process

Parameters of A/D converter: range of input signal

resolution (bits) - quantization error (%)10 bits = 210 = 1024 qantums= 0,1%

12 bits = 212 = 4096 qantums = 0,025%

sampling rate (sampling frequency)

conversion time (for one sample)

If a single converter services n inputs, than sampling rate = 1 / (n*conversion time)

Ux

t

Sampling

Analog signal

(continues in bothtime and amplitude)

Sampled-date signal

(discrete in time andcontinues in amplitude)

Quantization

Discrete timediscrete amplitude

si nal

Digital signal

Encodingu(t) u[k]

Minimum of sampling rate (Shannon-Kotielnikov sampling theorem*)

- theoretically: fs >= 2fw-practically: fs >= 2fb, (fb=10fw)

*Shannon-Kotelnikov, WhittakerNyquistKotelnikovShannon

fs sampling rate,

fx the highest frequency of the original signal

fb used pass band (gain>=0.7)

4.


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Integrating ADC (dual slope ADC)

Ux

Uw U1

US

K

GW

LU2 U3

T1 T2

U1

U2

U3Nx= Nmax

Nmax Nx

Ux

Uw

t

t

t

T1 T2

Ux Uw

Types

4.


65/82

ramp-compare ADC

Types

UX

U

Uout

tit

a direct-conversion ADC (flash ADC)

a successive-approximation ADC

a delta-encoded ADC or counter-ramp

a pipeline ADC (a subranging quantizer)

a sigma-delta ADC (a delta-sigma ADC)

a time-interleaved ADC

an ADC with intermediate FM stage

...

cfx

Forming Gate Counter

Controler

Pulse generator

Cancel

Nx

frequency-type ADC

frequencyinput

counting fxfor a determinate

time period

5.


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DAC

1 1 1

0 0 0X0 X1 Xi

21R 22R 2iR

U Uout

In: number X= X020 + X12

1 + ... + Xn2n

21R

22R

U

Uout

2 R

weigh-resistive

Out: signal Uoutif Xi=1 then switch=1

1 1 1

0 0 0

2R 2R 2R

U

X0 X1 Xi

Uout

2R2R

2R

2RU

Uout

2R

voltage ladder

...

.


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()

+ i

controller

sensor. measuring c. separating c. A/D

AD

()

+ + +

controller

sensor communication port

PAD

.


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TRCA154

H

process parameter

TRCA154

function: R - recordingI - indicationC - control

A - alarm

alarm

specification

TRCA154

D density

F flow rate

G distance, length, positionL level

P pressure

Q material properties

T temperature

W velocity, mass

programmable

deviceconfigurable

device

For further details, see DIN 19227

Graphical symbols and identifying letters in control engineering design

More: http://www.samson.deServicesTechnical Information

.


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Standards

US Standards:

ANSI Y32.2.3 Graphical Symbols for Pipe Fittings, Valves and Piping

ANSI Y32.2.11 Graphical Symbols for Process Flow Diagrams

ISA 5.5 Graphical Symbols for Process Displays

British Standards:

BS: 1646 1-4 Symbolic Representation for Process Measurement, Control

Function and InstrumentationGerman Standards:

DIN 19227 P1-P3 Graphical Symbols and Identifying Letters for Process

Measurement and Control Functions

Polish Standards:

PN-M-42007 (archive)

More: http://enormy.plhttp://www.samson.deServicesTechnical Information

.


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II. Actuating equipmenta) Final control element

1 valve

2 - pumpb) Actuator

1 - electrical motors

2 - pneumatic actuator

3 - hydraulic actuator

c

plant

sensor(sensing element)

measuringconverter

final controlelement


controller

A/D

converter

D/A

converter


supervisor system

controlled system

controlingsystem

Examples:

Actuating equipment (final control equipment): Control valve:

- final control element - valve (closure element, body of valve)- actuator - actuating driver

- positioner (measuring element)

Body of valve manipulates the mass and energy flow.

The opening or closing of control valve is usually done by electrical, hydraulic or pneumatic actuator.

Positioner is used to control the opening or closing of the actuator based on electric, or pneumatic signals.

.


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Final control element a part of the controlled system that manipulates the mass and

energy flow.

Classification valves according to function:

control valve

throttling (choke) valve

gate (sluice) valve safety-valve

reflux valve

Classification valves according to construction:

ball (globe) rotary (butterfly)

knife

neadle

flap

Basic type of final control element:

1) valves 2) pumps

Classification pumps according to principle of operation:

positive displacement pump

impulse pump

velocity pump

gravity pump

1.


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butterfly valve

(globe valve)

Inside a spherical discFeatures: simplicity, sealing

V-port ball valve ball valve(V-notch valve; a segmented ball valve )

Inside a spherical disc with a notchFeatures: simplicity, sealing, precise control

knife gate valve(quarter-turn valve)

Inside a metal disc mounted on a rodand positioned in the center of the pipe

Features: low cost, light

More: http://www.valtorc.comValves

Valve a device that manipulates the mass flow on basis of a throttling.

2.


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Pomp a device used to move fluids (liquids, gases, slurries) by mechanical actions

(often a reciprocating or rotary mechanism).

positive displacement pump

The pump moves a fluid by trapping a fixed

amount of it and then forcing (displacing) that

trapped volume into the discharge pipe

impulse pump

The pump use pressure created by gas (usually air) and pushing part of the liquid upwards

velocity pump

The pump increases the flow velocity thereby

kinetic energy and this energy is converted to

pressure

(rotodynamic pump, dynamic pump)

The velocity pump can be safely operated

under closed valve conditions

The positive displacement pump physically displaces the fluid

resulting in a continual build up in pressure and finally

mechanical failure of either pipeline or pump

Operation under closed valve conditions

screw

lobe

centrifugal

.


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Actuator - a type of motor for moving or controlling a mechanism (final control element).

It is operated by a source of energy (an electric current, hydraulic fluid pressure,

pneumatic pressure) and converts this energy into some kind of motion.

Basic type of actuator:

1) pneumatic actuator

2) hydraulic actuator3) motor-driven actuator (electrical servomotors)

Actuator processes and amplifies the output signal of controller

(effectors, servomotor)

Actuators are also known as:

effectors (in robotics)

servomotor linear actuator, rotary actuator

1.


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Principle: Pneumatic actuator converts energy of compressed air into a mechanical motion

diaphragm actuator

Actuator that has a chamber divided in half by a

diaphragm that separates areas with different

pressure levels.

bellow actuator

More: http://heating.danfoss.com

Self-acting thermostatic actuator

(e.g. used for temperature control)

pneumatic cylinder

3.


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Definitions:

actuator - a device converting a low-power signal into a large-force displacement

(linear or rotary )

motor a device converting a heat, electrical energy, mechanical energy into energy

to drive machines (usually electrical energy into energy of rotational motion)

Actuator

a large force

a small velocity

Motor

a small torque

a high velocity

Electric actuator (servomotor):

a) an electric motor + a gear

b) an electric motor giving a suitable displacement (e.g. stepper motor)

3.


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General principle: Lorentz force - any current-carrying conductor placed within an

external magnetic field experiences a torque or force

rotorstator

[http://www.allaboutcircuits.com/vol_2/chpt_13/1.html]

Classification:

3.


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series m.

MMM

shunt m. separately excited m.

+ - +

-

+ -

Principle: Statorwith a stationary magnets and the rotorpowered from a DC power by

brushes and commutator.

permanent magnets electromagnets

The type of connection determines the characteristics of the motor

Advantages: low initial cost, high reliability, simple control of motor speed

Disadvantanges: sparking and wear of the electric contact commutator-brushes

MN S

brushes

+ -

Magnetic fields of the stator and the rotor interact and a generated torque causes a turn of the rotor.

The commutator consisted of a split ring reverses the current each half turn of the rotor.

Control:- the sense of rotation depends on the polarity of the excitation winding control by change of the polarity

- the rotational speed is proportional to the EMF in its coil - control by variable supply voltage, resistors or

electronic controls (e.g. PWM)

- the torque is proportional to the current

3.


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Principle: Rotorwith a stationary magnets and the statorpowered from the AC power

and generating a rotating magnetic field.

single phase s.m. stepper m.

Advantages: speed independent of the load,

accurate control in speed and position for stepper motor

Disadvantanges: above a certain size, synchronous motors are not self-starting motors

Electromagnets on the stator create the magnetic field which rotates in time with the oscillations of the

line current and the rotor turns in step with this field, at the same rate (the motor speed is synchronized

with the frequency the AC supply current )

Control:- sense of rotation depends on the direction of rotating magnetic field control by change of the phase order

- motor speed is synchronized with the supply frequency control by a variable-frequency driver

MN

S

three-phase s.m.

M

3.


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Principle: Rotorcontained no powered circuit and the statorpowered from the AC power

and generating a rotating magnetic field.

wound-rotor induction motor squirrel-cage rotor induction motor

Advantages: ruggedness, simplicity, 90% of industrial motors are induction m. (mainly the squirrel-cage rotor)

Disadvantanges: hard starting (it is accompanied by inrush currents up to 7 times higher than running current)

Electromagnets on the stator create the rotating magnetic field which induces an electric current in the

windings of rotor. Interaction between magnetic fields of stator and rotor produces a torque. The rotor

rotates at a slower speed than the stator field

Control:

-sense of rotation depends on the direction of rotating magnetic field control by change of the phase order

- motor speed is proportional to supply frequency control by a variable-frequency driver.

U W

V

MM

U W

V

(asynchronous motor)

Windings of rotor brought out via slip rings and

brushes which allows to connect a resistance during

start-up and to short-circuit windings during work.

Windings of rotor in the form of cage (poured

or welded)

Starting with:

star-delta switch

motor soft starter

3.


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A variable-frequency drive (VFD)

(adjustable-frequency drive, variable-speed drive, AC drive, micro drive, inverter drive)

- a type of adjustable-speed driver used to control AC motor speed and torque by

varying motor input frequency and voltage

electronic - frequency converter (frequency changer)

electromechanical = motor + generator

A motor soft starter

- a device used with AC electric motors to temporarily reduce the load and torque in thepowertrain of the motor during startup. This reduces the mechanical stress on the motor

and shaft, as well as the electrodynamic stresses on the attached power cables and

electrical distribution network, extending the lifespan of the system


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The main topics:


II. Actuating elements------------------------------------------

I. Field devices - controllers

II. Communication networks

III. SCADA & DCS

}Instrumentation of a technological process

15 hours

} 15 hours

industrial control system czemplik

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