EMCS Technology Solutions V2

Process Control System EN 02/06

Solutions for

Courseware

Process Control

System

2 © Festo Didactic GmbH & Co. • Process Control System

This courseware has been developed and manufactured exclusively for vocational

and continuing training in process automation and control engineering.

The training company and / or trainers have the duty to ensure that trainees observe

all safety precautions described in the accompanying manuals and data sheets.

Festo Didactic GmbH & Co. and ADIRO Automatisierungstechnik GmbH will not be

liable for any damage or injury to trainees, the training company and / or other third

parties resulting from use of the equipment for any other purpose than training,

unless Festo Didactic GmbH & Co. or ADIRO Automatisierungstechnik GmbH has

caused such damage or injury willfully or through negligence.

Order no

Designation Courseware

Description Exercises for process and control engineering

Status 03/2005

Authors Jürgen Helmich, Stefan Knoblauch, Andreas Wierer (ADIRO)

Translation Williams Technical Communication Pty Ltd, Brisbane

Graphics Jürgen Helmich, Stefan Knoblauch (ADIRO)

Layout Jürgen Helmich (ADIRO)

© Festo Didactic GmbH & Co., 03/2005

Internet: www.festo.com/didactic http://www.festo.com/didactic/de/ProcessAutomation

e-mail: [email protected]

The copying, distribution and utilization of this document as well as the communication of its contents

to others without expressed authorization is prohibited. Offenders will be held liable for the payment of

damages. All rights reserved, in particular the right to carry out patent, utility model or ornamental

design registration.

Intended application

© Festo Didactic GmbH & Co. • Process Control System 3

Solutions for process and control engineering _____________________________ 5

Solution for Exercise 2.2 _______________________________________________ 5

Solution for Exercise 2.3.1______________________________________________ 9

Solution for Exercise 2.3.2 _____________________________________________ 13

Solution for Exercise 2.3.3 _____________________________________________ 14

Solution for Worksheet 3.1.1 ___________________________________________ 18










Solution for Worksheet 3.6.1 for Siemens BE.SI.0193 ultrasound sensor _______ 32

Solution for Worksheet 3.6.1 for Festo 170710 ultrasound sensor _____________ 33





Contents

Contens

4 © Festo Didactic GmbH & Co. • Process Control System




Solution for Worksheet3.9.2____________________________________________ 41

Solution for Worksheet 3.10____________________________________________ 42

Contens







Solution for Worksheet 4.2.4___________________________________________ 57









Solution for Worksheet5.1.1____________________________________________ 69





© ADIRO Automatisierungstechnik GmbH • Process Control System 6

• Which components are necessary for the chosen close-loop control system?

Components

PLC / controller

Tank X

pressure gauge

pump X

ultrasonic sensor X

pressure sensor

flow rate sensor

temperature sensor

proportional valve

industrial controller X

proximity switch

float switch, overflow

float switch for raising level

pressure tank X

SCADA X

piping and hand valves

heating

Solutions for Courseware Process Control System

Solution for

Exercise 2.2

Equipment list

for level

Solutions for process and control engineering


Components

PLC / controller

Tank X

pressure gauge

pump X

ultrasonic sensor

pressure sensor

flow rate sensor X

temperature sensor

proportional valve


proximity switch



pressure tank X

SCADA X

piping and hand valves

heating

Equipment list

for flow rate


8 © ADIRO Automatisierungstechnik GmbH • Process Control System

Components

PLC / controller

Tank X

pressure gauge

pump X

ultrasonic sensor

pressure sensor X

flow rate sensor

temperature sensor

proportional valve


proximity switch



pressure tank X

SCADA X

piping and hand valves X

heating

Equipment list

for pressure



Components

PLC / controller

Tank X

pressure gauge

pump X

ultrasonic sensor

pressure sensor

flow rate sensor

temperature sensor X

proportional valve


proximity switch



pressure tank X

SCADA X

piping and hand valves X

heating

Equipment list

for temperature



PI-diagram for level.

B101

B102

LIC

102

LA+

101.3

LS-

102

V101

V112

V105

P101

M

V102

LS-

101.1

LS+

101.2

Solution for

Exercise 2.3.1



PI-diagram for flow rate.

B101

LA+

101.3

V105

LS-

101.1

LS+

101.2

FIC

101.1

V104

V109 V103

V106

P101

M



PI-diagram for pressure.

B101

LA+

101.3

V105

LS-

101.1

LS+

101.2

V109 V103

V106

P101

M

PIC

103

B103

V108

V107



PI-diagram for temperature.

B101

LA+

101.3

V105

LS-

101.1

LS+

101.2

V109 V103

P101

ME104

TIC

104



EMCS point list for level controlled system.

1 2 3 4 5 6 7 8 9 10 11 12 13 14

DN R-KL

PN D-KL

Rltg./Ap.Stutz

material valuet

°CRange ∆p

pressure

absoluteFlow rate

PCS.

EMCS-point

Revision

Component

symbolEMCS task

Place

1

Ultrasonic-

sensor

B101

Measure level 4..20mA

transform signal

F

Transformer

A1

1 S

1

Controller

E/E

N1

proportional controller

1

Relay

K1

preselect pump

Applifier

A41

transform signal

and power

1Pump

M1control level

C

S

S

F

4...20mA/

0...10V

PI

4..20mA

0...10V

0...6 l/min

digital (0)/

analog (1)

0...10V

0...24V

LIC102

P101

level controlled system EMCS point list - solution

Solution for

Exercise 2.3.2



EMCS point list for flow controlled system.

1 2 3 4 5 6 7 8 9 10 11 12 13 14

DN R-KL

PN D-KL

Rltg./Ap.Stutz

material valuet

°CRange ∆p

pressure

absoluteFlow rate

PCS.

EMCS-point

Revision

Component

symbolEMCS task

Place

1Flow rate sensor

B102Measure flow rate 40...1200 Hz 0,3...9,0 l/min

transform signal

F

Transformer

A21 S

1

Controller

E/E

N1


1Relay

K1pre-select pump

Amplifier

A41

transform signal

and power

1Pump

M1Control flow rate

C

S

S

F

0...1000 Hz/

0...10 V

PI

4..20 mA

0...10 V

0...6 l/min

digital (0)/

analog (1)

0...10 V

0...24 V

FIC101.1

P101

flow rate controlled system EMCS point list - solution



EMCS point list for pressure controlled system.

1 2 3 4 5 6 7 8 9 10 11 12 13 14

DN R-KL

PN D-KL

pressure controlled system EMCS point list - solution

P101

PIC103

0...10 V

0...24 V 0...6 l/min

digital (0)/

analog (1)

PI

4..20 mA

0...10 V

S

S

FPump

M11 Control flow rate

1Relay

K1pre-select pump

1Amplifier

A4

transform signal

and power


F

Controller

E/E

N1

1 C

1Pressure sensor

B103Measure pressure 0...400 mbar

PCS.

EMCS-point

Revision

Component

symbolEMCS task

Place

Range ∆ppressure

absoluteFlow rate

Rltg./Ap.Stutz

material valuet

°C



EMCS point list for temperature controlled system.

1 2 3 4 5 6 7 8 9 10 11 12 13 14

DN R-KL

PN D-KL

temperatur controlled system EMCS point list - solution

P101

TIC104

0 V / 24 V0 l/min /

6 l/min

digital (0)/

analog (1)

PI

4..20 mA

0...10 V

C

F

S

S

1 control circulation

1Relay

K1pre-select pump

1

Controller

E/E

N1

Controller, un-steady

2-point control Heating

1Relay

K_E104Control heating

Pump

M1

transform signal

F

Transformer

A31 S

1

Temperatur

sensor

B104

Measure temperaturePT100

80...150 Ohm-50...+150°C

PCS.

EMCS-point

Revision

Component

symbolEMCS task

Place

0/24V /

Heating

ON/OFF

Rltg./Ap.Stutz

material valuet

°CRange ∆p

pressure

absoluteFlow rate

0...100 °C/

0...10 V



EMCS point plan for level controlled system.

ML

PID

X2.8

X2.3

X2.2

X2.6

B102

N1

5...300 mm

0...10V

4...20 mA

5 6

A1

2 4

U

I

0...10V

0...24 V

23 22

A4

14 13

U

U

12 14

11

K1

A2 A1

M1

P101

Solution for

Exercise 2.3.3



EMCS point plan for flow controlled system.

M

PID

X2.7

(UE2)

X2.3

X2.2

(UA1)

X2.6

B102

N1

40...1200 Hz

0...10V

0...1000 Hz

5

(Out)

6

(0V)

A2

2

(IN+)

4

(IN-)

U

f

0...10V

0...24 V

23 22

A4

14 13

U

U

12 14

11

K1

A2 A1

M1

P101

F



EMCS point plan for pressure controlled system.

M

PID

X2.15

(UE3)

X2.3

X2.2

(UA1)

X2.6

B103

N1

0...400 mbar

0...10V

0...24 V

23 22

A4

14 13

U

U

12 14

11

K1

A2 A1

M1

P101

P



EMCS point plan for temperature controlled system.

X2.14

(UE4)

X2.3

XMA.2

XMA.11

B104

N1

-50...+150°C

0...10V

0...100 °C

Out 0V

A3

1 3

U

T

2 1

E104

T

2

14

13

NLPE

230V

XMA.0 VA XMA.Q1



The task is to calculate the volume of the container and to establish the relationship

between volume and level.

To calculate the container volume, refer to the data sheet. Here you will find the

internal dimensions of the container. If this data is used to calculate the maximum

volume, the result is:

Container height h = 300 mm

Container width w = 190 mm

Container depth d = 175 mm

Volume at level 300 mm or 100 mm

llmmmmmmmm 10975,9000.975.93001750193

≈==⋅⋅

ldm 113=

l 3.325mm 100 reads scale when Volume a⇒

mlmm 331 a⇒

When the scale reads 300 mm, the volume of medium in the container is 10l.

Solution for

Worksheet 3.1.1

Where:

Find:

Solution:



The pump is a normally primed centrifugal pump. This type of pump requires an

absolutely tight suction pipe that should always be inclined up away from the pump

in order to prevent the formation of air pockets. The pump and suction pipe must be

filled with medium.

The following points must be taken into account during operation:

Before operation, the pump must be filled with medium.

The pumps must not run dry – but a dry-running period of less than 30 minutes will

not damage the pump.

The pump must always run in the prescribed direction.

The pump is suitable for continuous operation.

The medium to be pumped should not contain large particles of contaminant.

1.1.1 Calculating the rated current

VV 24= WP 26=

The rated current of the pump

AV

W

V

PIIVP 083.1

24

26===⇒⋅=

Solution for

Worksheet 3.2.1

Where:

Find:

Solution:



Exploded drawing of the pump

No. Part designation

1 Housing, ø 20

2 Rotor disk

3 O-ring

4 Screw

5 Motor bracket

6 Washer

7 Shaft

8 Seal

9 Magnet housing

Solution for

Worksheet 3.2.2



To determine the delivery rate of the pump, water is pumped from the lower

container to the upper container until the level reads 150 mm on the scale. This

allows the average flowrate per unit time (volumetric flow) to be determined.

The pump capacity is to be calculated with the aid of the volumetric flow and the

delivery head.

Procedure

1. Commission the system: fill and vent.

2. Switch on power supply.

3. Close the outlet of the upper container of the level-controlled system.

4. Switch pump ON (with Process Lab, SPS or controller) and start timer.

5. When level of 150 mm on the scale is reached, stop timer.

6. Read off actual scale value (if not exactly 150 mm).

7. Determine and document pumping time and delivery head.

8. Determine average flowrate.

9. Determine pump capacity.

Result 1

35

mm

61,5 s

Result of pump speed measurement

Solution for

Worksheet 3.2.3



Measured values from diagram:

Pumping time s5,61tF=

Delivery head mm135hF=

Container width mmw 190=

Container depth mm175l =

Calculation of volumetric flow s V& :

min38.4

min260.379.4

608.72987

8.729875.61

4488750

5.61

175190135

33

33

lmm

s

mmV

s

mm

s

mm

s

mmmmmm

t

lwh

t

VV

F

F

==

⋅

=

==

⋅⋅

=

⋅⋅

==

&

&

The volumetric flow is the volume flowing through the cross-sectional area per unit

time.

The capacity of the pump can be calculated with the following formula:

hgVP ⋅⋅ρ⋅= & with 2

81.9s

mg =

The system comprises a low and a high container and a pump between them. The maximum delivery head hmax is the distance between the inlet port of the pump and the maximum delivery head in the upper container hoB, less the minimum suction height in the lower container huB in relation to the surface of the profile plate.

Distance pump inlet – maximum delivery head in the upper container:

mm35mm145mm350hoB −+= =460mm

Minimum suction height:

mm120mm35mm155huB =−=

The maximum delivery head hmax is:

mm340mm120mm460hhh uBoBmax =−=−=

The density of water is 33

0.100000.1m

kg

dm

kg==ρ



This results in the following calculation for the capacity of the pump:

Ws

Nm

s

mkgw

sms

mmkgmP

ms

m

m

kg

s

mhgVP

33

2

23

3

3

23

3

3

max

1045.2431045.243P

unit in the resulting Nith

1045.243

340.081.910001099.72

−−

−

−

⋅=⋅=

⋅

=

⋅⋅

⋅⋅⋅

⋅=

⋅⋅⋅⋅=⋅⋅⋅= ρ&

Explanation of the result

No general solution for the capacity of the pump can be given as the value varies

from system to system. Component tolerances in the pump, the setting of the motor

regulator operating characteristic as well as differences in the piping system (curves,

pumping head) can result in different delivery rates.


What does the term proportional valve mean?

The solenoid valves are closed by a spring at zero current. Any current through the

solenoid coil results in a state of equilibrium between the spring and the magnetic

force. The strength of the solenoid current or the magnetic force determines the

stroke of the armature or degree to which the valve is opened. Ideally,

dependency between current and opening of the valve should be linear. In other

words, the valve opens and closes to a degree proportional to an analog voltage

in the range 0 to 10 V.

What electrical signals do you need to use a proportional valve?

The electronics of the proportional valve require a supply voltage of 24 VDC.

The valve is opened or closed with a control voltage of 0 to 10 V.

Solution for

Worksheet 3.3.1


© Festo Didactic GmbH & Co. • PCS 29

What is the maximum rate at which you can pump the medium used through the

proportional valve?

The throughput capacity of a control valve is to be determined.

The maximum flowrate is calculated from the KV value and the pressure drop across

the valve:

KVS value h

mK

VS

3

33.0= Proportional valve

data sheet

Delivery pressure barp 3.0= Pump data sheet

Volume flowrate min

0.9l

V =& Pump data sheet

Find:

Maximum flowrate

Solution:

min74.2

min74.2

min1074.210164164.0

1000

3.033.06.31

m

kg1000ρ and0.3bar ∆pwith

6.31

33

3

3

3

3

3

3

ldmm

h

m

h

mV

h

mV

pKV

VS

==⋅=⋅==

⎥⎦

⎤⎢⎣

⎡⋅⋅=

==

∆⋅⋅=

−−

&

&

&

ρ

The flowrate determined with Process Lab: min

3.2l

V =&

What possibilities are there for adjusting this valve?

You can set the maximum and the minimum flowrate through the valve via the

Solution for

Worksheet 3.3.2

Where:



electronics with the aid of potentiometers R1 and R2.


Equipment list for the process drive module

Item. Process drive equipment list Type Quantity

1 Ball cock ½" 1

2 Reducing sleeve SW9/SW11 1

3 Mounting bracket with cheese-head screws ALU 1

4 Semi-rotary drive Sypar 1

5 Namur solenoid valve 1

6 Exhaust-air flow control valve with integrated

silencer

2

7 Quick push-pull elbow G1/4 1

8 Solenoid valve 1

9 Socket with connecting cable 3-wire 1

10 Sensor box with connecting cable 6-wire 1

What electrical signals do you need to work with the process drive?

A digital signal for the solenoid valve ( (24V: switch ON, 0V: switch OFF)

Give a brief description of the module’s mode of operation..

Solution for

Worksheet 3.4.1



A coil is energized by an electrical signal. This operates the Namur valve

magnetically. The semi-rotary drive moves through 90° as the result of the

compressed air switched by the valve. This opens or closes the ball cock.



What function does the sensor box fulfill? Name the signals you receive from the

sensor box and, where appropriate, how you can record these signals.

The sensor box delivers three signals

1) a visual signal, red and yellow. Red means “Ball clock closed” and yellow

means “Ball cock open”.

2) A digital signal to I5 (digital input of the I/O terminal) “High” means “Ball cock

closed”.

3) A second digital signal to I6 (digital input of the I/O terminal): “High” means

“Ball cock open”.

Solution for

Worksheet 3.4.2



What type of drive is it?

How does it work?

It is a semi-rotary drive with a scotch yoke. When the process valve is opened, the

pistons move to the end caps. When the process valve is closed, the piston moves

toward the shaft.

The torque is generated by the scotch yoke. In contrast to rack and pinion drives

is not constant throughout the angle of rotation.

Benefit: The high breakaway torque of the valve is overcome.

The range of motion of the drive is limited to 90° for use with equipment such as

ball cocks and butterfly valves.

Function diagram

Solution for

Worksheet 3.4.3



What are all the things you have to take into account when using the heating

element??

The heating element may only be switched on if it is entirely immersed in fluid.

The heating element is hot!

Calculate the rated current of the heating element.

The following values are to be taken from the data sheet:

Rated voltage: V230

Heat output at rated voltage: W1000

Rated current of the heating element.

AV

W

uPi 35.4

230

1000≈==

Solution for

Worksheet 3.5.1

Caution!

Where:

Find:

Solution:



The sensor characteristic of the ultrasound sensor was recorded with FluidLab-PA.

The relationship between the sensor signal and the container level can be derived

from the characteristic.

Characteristic of the Siemens ultrasound sensor with FluidLab-PA

Operating range of the Siemens ultrasound sensor, programmed by ADIRO

Solution for

Worksheet 3.6.1 for

Siemens BE.SI.0193

ultrasound sensor



Solution and background – Determining the mode of operation of an ultrasound

sensor

It must be borne in mind that some transducers and PLCs can only read or deliver an analog signal as a voltage signal in the range 0 to 10 V. In this case, signal conversion is required. The analog ultrasound sensor used in this system deliver an analog current signal of 4 to 20 mA based on the distance measured. This can be converted into a voltage signal by means of a load resistor. The description of the sensor indicates that the load resistor RL must be less than 400 Ω. If, for example, RL = 390 Ω, the resulting

voltage signal is in the range 2.34 to 7.80 V.

Bildtexte: U Meß = Vmeas.

Transducing a signal – for example, with the aid of a resistor

Solution for

Worksheet 3.6.1

for Festo 170710

ultrasound sensor



Recording the characteristic of an ultrasound sensor

Level [mm] Signal [V]

20 4.46

40 5.49

60 5.5

80 5.62

100 6.03

120 6.43

140 6.78

160 7.13

180 7.52

200 7.82

220 8.18

240 8.51

260 8.75

280 8.8

300 8.82

Bildtexte: Level (mm)

2.00 4.00 etc.

Solution for

Worksheet 3.6.2



Background to the exercise

The technical description of analog sensors normally gives the sensor’s characteristic (graphically, or as an equation with tolerances).

If the characteristic is not given, it must be established experimentally. This may

also be necessary when operating conditions have an impact on the characteristic.

The location of the sensors – that is, its attitude and height above the container – is

of great importance for a level control. The distance measured is between the sensor

head and the water’s surface – and not the actual level.

Bildtexte Ultrasound sensor

Location of the ultrasound sensor

d Minimum distance between the sensor

and the surface to be measured

hB Measuring range

h Height of the surface

a Distance between the surface and the sensor

The characteristic shows that the sensor's signal is only linear in a certain range.

When doing later exercises with the ultrasound sensor, it must be ensured that the

level in the container is approx. 180 mm and that it remains within the usable range

of the sensor.



The medium flowing through the flowmeter drives a rotor. The sensor delivers a

square-wave signal proportional to the rotational speed of the rotor. This sensor

signal can be measured with an oscilloscope.

The lower limit of the measuring range is 0.3 l/min.

The upper limit of the measuring range is 9.0 l/min.

The values are shown in the data sheet.

Flowrate [l/min] Frequency [Hz] Calculated height

after 1 min

Measured height

after 1 min

1 133 30

2 266 60

3 400 90

4 532 120

5 665 150

6 798 180 Not possible





Not possible = Insufficient pump capacity

Solution for

Worksheet 3.7.1

Measured-value table



1.1.2 From data sheet

K factor: l

pulsesdm

pulses80008000 3 =

Measuring range: min

0.93.0 l−

1.1.3 Calculation

For Hzpulsesl 40

sec140

min2400

min3.0 ==⇒

For Hzpulsesl 1200

sec11200

min72000

min0.9 ==⇒

Flowrate (l/min)

Frequency (1/s)

100 200 300 400 500 600 700 800 900 1000 1100 1200

1

2

3

4

5

6

7

8

9

10

Du

rch

flu

ss [

l/m

in]

Frequenz [1/s]

Solution for

Worksheet 3.7.2



The analog pressure sensor is a piezoresistive relative pressure sensor with integrated amplifier and built-in temperature compensation in an aluminum housing. The pressure to be measured acts on the piezoresistive element. The resulting signal change is emitted via an integrated amplifier as a voltage at the connector. The maximum output voltage is 10V DC. The output signal can be measured with a voltmeter. The temperature of the medium to be measured must be within a certain range, namely between –25°C und 100°C. The measuring range is between 0 and 100 mbar or 0 and 400 mbar, depending on the sensor type (see data sheets).

Solution for

Worksheet 3.8.1



0

2

4

6

V

10

U

P

-1 0 20 40 60 mbar 100

Characteristic of the pressure sensor 167224

Pressure [mbar] Voltage [V]

0 0

10 1

20 2

30 3

40 4

50 5

60 6

70 7

80 8

90 9

100 10

Measured-value table for pressure sensor 167224

Solution for

Worksheet 3.8.2



Characteristic of pressure sensor BE.EL.0600

Increase the voltage at the pump until the desired pressure value is shown on the

manometer.

Pressure [mbar] Voltage [V] Comment

0 0

50 1.25

100 2.5

150 4.75

200 5.0

250 6.25

300 7.5 Not possible

350 8.75 Not possible

400 10 Not possible

Measured-value table for pressure sensor BE.EL.0600

This exercise involves examining the temperature sensor.

Pt stands for the material out of which the measuring resistor is made.

Solution for

Worksheet 3.8.2

Solution for

Worksheet 3.9.1



• Pt: Platinum,

• Ni: Nickel.

100 stands for the resistance in Ohms, when the measuring resistor has a

temperature of 0°C.

There are also Pt1000 Sensors. Logically, these have a resistance of 1000 Ohm at a

reference temperature of 0°C.

The temperature coefficient of the sensors is uniform at 3850 ppm/K. That means

the internal resistance of the sensor changes by 0.385% for each degree change in

temperature.

Based on these values, the resistance of the Pt100 at 100°C can be calculated as

follows:

Temperature change from

%5.38%385.0100 100100t0 =⋅⇒=°°K

K K C o C

Ω=Ω+Ω=∆+=⇒Ω=∆⇒°°

5.1385.381005.381000100100 KCCK

RRRR

The measuring resistor can be measured with an ohmmeter.

ϑ/°C

R/Ω

Temperature [°C] -100.00 0.00 100.00 200.00

Value [Ω] 60.25 100.00 138.50 175.84

Solution for

Worksheet3.9.2



• What result do you expect?

Level [mm] Time [s] Level [mm] Time [s]

10 ----- 160 28

20 0 170 30

30 2 180 32

40 4 190 34

50 6 200 36

60 8 210 38

70 10 220 40

80 12 230 42

90 14 240 44

100 16 250 46

110 18 260 48

120 20 270 50

130 22 280 52

140 24 290 54

150 26 300 56

Solution for

Worksheet 3.10

Measurement 1:

Inlet valve open, outlet valve

closed, pump running



Inflow characteristic with FluidLab-PA - Inlet valve open, outlet valve closed



• What result to you expect?


300 0 150 87

290 5 140 96

280 10 130 104

270 15 120 112

260 20 110 118

250 25 100 130

240 31 90 138

230 38 80 150

220 44 70 162

210 50 60 175

200 56 50 187

190 63 40 200

180 69 30 225

170 75 20 250

160 81 10 -----

Measurement 2:


closed, pump not running



Outflow characteristic with FluidLab-PA – inlet valve open, outlet valve closed



• What result to you expect?


10 ----- 160

20 0 170

30 8 180

40 19 190

50 30 200

60 44 210

70 60 220

80 77 230

90 100 240

100 131 250

110 168 260

120 212 270

130 280 280

140 290

150 300

Measurement 3:


open, pump running



Inflow characterstic with FluidLab-PA – inlet valve open, outlet valve open



Bildtexte: Level (mm) 1. Inflow t8s), V2 closed 2. Outflow t(s) 3. Inflow t(s), V2

open

Characteristics for container inflow and outflow

Findings from Measurement 1

The outlet valve V102/V112 is closed. As a result inflow via the inlet valve V101, the

increase in the level (h) in the container is steady and linear over time. The greater

the inflow, the more quickly the level in the container increases per unit time. If the

quantity of water in container B101 were not limited, the amount of water would

continue to increase until the container overflowed. There is not self-stabilization

here. For this reason, the closed container B102 is an uncompensated controlled

system.

These uncompensated controlled systems are also termed integral systems (I

systems), because the feed quantities add up.

The level is thus the sum of all water that flows into the system. The time from empty

to full is therefore also called the integration time Ti. Typical integral systems in

machine-building are hydraulic cylinders and threaded spindles.



Findings from Measurement 2

The hydrostatic pressure in the water column ensures a reduction of flowrate at the

outlet. The lower the water column, the lower the hydrostatic pressure and thus the

lower the amount of water outflow. This results in a non-linear characteristic.

Example: Electrical engineering: discharge of a capacitor

Finding from Measurement 3

Controlled systems with compensation are controlled systems whose characteristic

reaches equilibrium after a time.

In level-controlled systems, the compensation takes the following physical form.

When filling with a constant flowrate (inflow), the pressure of the water column at

the bottom of the container is proportional to the level.

The pressure at the bottom increases with level. This results in an increase in

outflow until equilibrium with the inflow is reached. This results in a constant level -

that is, it no longer increases. This is called a steady-state end value.

Outflow flowrate of water = inflow flowrate

Controlled systems with equilibrium are also called PT controlled systems:

P – because the steady-state value is proportional to the input vale

T – because the steady-state value is only reached after time T

If only container (controlled system) is present, the controlled system is called a PT1

= 1st order controlled system. A controlled system of the 0th order would be a pure

P system, for example, a lever: the force is transmitted immediately without any

delay.



• Are you using close-loop or open-loop control of the level?

The level is close-loop controlled..

• Is it possible to maintain a constant level manually?

It is very difficult to maintain the level accurately.

Pump voltage measured at mean measured value

Mean

measured value

[mm]

Pump voltage

[V]

Solution for

Worksheet 4.1.1



Determining the operating range and operating point of the control

Level

h [mm]

Sensor signal

I [mA]

Transducer

output signal

U [V]

Max. measured value 25

Mean measured value 150 5

Min. measured value 300 10

The mean measured value can be taken as the operating point for the dynamic

response of the control. The operating point should always be in the linear part of

the sensor characteristic. The relationship between the input variable and the

output variable – that is the actual value and the manipulated variable – is

determined for the static response of the control when stationary. The manipulated

variable should also be in the linear part of the actuator (pump).

Transient response of a level-controlled system (Compact Workstation) – static response

Solution for

Worksheet 4.1.2



A functioning control always comprises at least two elements: a controller and a

controlled system. For control tasks it is essential to know which variable in the

system is to be controlled.

In a level-controlled system, the controlled variable is the level – its current status

(actual value) is interrogated by a sensor.

How does the system respond with the outlet valve closed?

The level (actual value) slowly approaches the setpoint.

Once the setpoint is reached, the controller ensures that the speed of the pump is

reduced as required to maintain the desired level.

How does the system respond with the outlet valve open?

Opening the outlet valve acts as a disturbance variable. Water is suddenly removed

from the container. The level of the container is maintained, however. The pump

runs faster (higher RPM) than with the outlet valve closed.

Background

The controller has the task of controlling the system in such a way that the

controlled variable (that is, the level), remains as constant as possible. In the event

of a disturbance (sudden removal of water), the controller increases the speed of the

pump to pump more water into the container and thus compensate the loss.

The controller is informed of a change in level by the signal from the sensor. This

signal is termed the actual value.

Solution for

Worksheet 4.1.3



Dynamic response – setpoint step-change to operating point with PI controller, outlet valve open



It is not possible to maintain a constant flowrate manually.

Determining the measuring chain of the flow-controlled system with a pump as

final control element

Flow-controlled system

Pump operating range

Sensor Transducer

Flowrate

Q [l/min]

Signal

f [Hz]

Flowrate

Q [l/min]

Flowrate

Q [l/min]

Signal

f [Hz]

Flowrate

Q [l/min]

MAX 4.3 266 9.0 1200 1000 10.0 7.5

MIN 0.0 0.0 0.4 50 0.0 0.0 0.0

Determining the flowrate characteristic of the pump (light blue = pump voltage, green = flowrate)

Solution for

Worksheet 4.2.1

Solution for

Worksheet 4.2.2



Mean value of the operating range of the control system with a pump as the final

control element

Mean measured value

[l/min]

Dimensionless value

[ 0.0 – 1.0 ] Pump voltage

[V]

2,0 0,35 6,0

Convert the measured value into a dimensionless value in the range [0-0 – 1.0]. This

means that the maximum measurable pressure of 400 mbar would have the value

1.0.

System response for a flow-controlled system with pump at operating point, input voltage jump of 6.0V



System response for a setpoint jump of a flow-controlled system with a pump and PI controller

Solution for

Worksheet 4.2.3



Determining the operating range of a flow-controlled system with a proportional

valve as final control element

Flow-controlled system

Proportional value

operating range

Sensor

Transducer

Signal

f [Hz]

Flowrate

Q [l/min]

Output

signal

f [Hz]

Signal

f [Hz]

Flowrate

Q [l/min]

Output

signal

f [Hz]

Signal

f [Hz]

MAX 2.3 306 9.0 1200 1000 10.0 7.5

MIN 0.0 0.0 0.4 50 0.0 0.0 0.0

Determining the flowrate characteristic of the proportional valve (light blue = pump voltage, green = flowrate)

Solution for

Worksheet 4.2.4



Mean value of the operating range of the control system with a proportional valve

as the final control element

Mean measured value

[l/min]

Dimensionless value


[V]

1,2 (153 Hz) 0,15 6,0

System response for a flow-controlled system with proportional valve at operating point, input voltage jump of

5.0 V.



System response for a setpoint jump of a flow-controlled system with a proportional valve and a PI controller

Solution for

Worksheet 4.2.5



It is not possible to maintain a constant pressure manually.

Determining the measuring chain of a pressure-controlled system with a pump as

final control element

Pressure-controlled system


Sensor

Measuring range

Pressure

p [mbar]

Signal

U [V]

Pressure

p [mbar]

Signal

U [V]

MAX 220 5.45 400 10V

MIN 0 0.0 0 0.0

Determining the pressure characteristic of the pump (light blue = pump voltage, green = container pressure)

Solution for

Worksheet 4.3.1

Solution for

Worksheet 4.3.2



Mean value of the operating range of the pressure-controlled system with a pump

as the final control element

Mean measured value

[l/min]

Dimensionless value


[V]

110 0.28 8.0

Convert the measured value into a dimensionless value in the range [0-0 – 1.0]. This

means that the maximum measurable pressure of 400 mbar would have the value

1.0.

System response for a pressure-controlled system with pump at operating point, input voltage jump of 8.0 V



System response for a pressure-controlled system with pump and PID controller

Solution for

Worksheet 4.3.3



Determining the operating range of the pressure-controlled system with a

proportional valve as final control element

Pressure-controlled system


Sensor

Measuring range

Signal

[V]

Pressure

p [mbar]

Signal

[V]

Pressure

p [mbar]

MAX 210 5.35 400 10V

MIN 0 0.0 0 0.0

Determining the pressure characteristic of the proportional valve (light blue = pump voltage, green = container

pressure)

Solution for

Worksheet 4.3.4



Mean value of the operating range of the pressure-controlled system with a

proportional valve as the final control element

Mean measured value

[l/min]

Dimensionless value


[V]

105 0.26 1.3

System response for pressure-controlled system with proportional valve at operating point, input voltage jump

1.3 V



System response for a setpoint jump of a pressure-controlled system with a proportional valve and PID controller

Solution for

Worksheet 4.3.5



The order of the controlled system can be determined from the transient response

curve of the controlled system:

Transient responses of systems of different order

Once the order of the controlled system has been established, the time constant T of

the controlled system can be determined graphically. For controlled systems of the

1st order, the time constant is determined as follows:

Bildtexte S = output variable When t = T, T = 63%

Determining the time constant

Solution for

Worksheet 5.1.1



Bildtexte:

The irrational number e – the characteristic value for a steadily decreasing rate of

increase – calculated?

The number e is the final value of the series:

Final value

Time steps

e = 2.71832 (bitte Dezimalpunkt statt –komma verwenden)

How is the number e, the

In the language of mathematics, the time constant is also termed a subtangent.

PT1 elements smooth fast-changing signals (high frequencies) but let low

frequencies pass. For this reason, they are also known as low-pass filters of the first

order. They also generate a phase shift between the input signal and the output

signal.

The determination of time constants for higher-order controlled systems is

described in detail in the workbook “Control of temperature, flowrate and level),

Chapter 2.3.3, Process analysis and modelling” .

The controlled system is in steady state after 5T.

A controller for the controlled system should always be 8 – 10 times faster than the

time constant to allow correct control.



Transient response of the level-controlled system at the operating point

The transient response of the level-controlled system is shown as an example.

Please note that the same measurement taken on different systems can lead to

deviation. Such deviation is caused by component tolerances .The measurement

was made using the Compact Workstation level-controlled system and recorded with

FluidLab-PA and EasyportDA.

The level-controlled system (with open discharge valve) is a controlled system of the

first order.

Solution for

Worksheet 5.1.1



Transient response of the flow-controlled system at the operating point

The transient response of the flow-controlled system with a pump as final control

element is shown as an example. Please note that the same measurement taken on

different systems can lead to deviation. Such deviation is caused by component

tolerances. The measurement was made using the Compact Workstation level-

controlled system and recorded with FluidLab-PA and EasyportDA.

The flow-controlled system is a controlled system of the first order.

Solution for

Worksheet5.1.1



Transient response of the pressure-controlled system at the operating point

The transient response of the pressure-controlled system with pump as final control

element is shown as an example. Please note that the same measurement taken on

different systems can lead to deviation. Such deviation is caused by component

tolerances. The measurement was made using the Compact Workstation level-

controlled system and recorded with FluidLab-PA and EasyportDA.

The pressure-controlled system is a controlled system of the first order.

Solution for

Worksheet 5.1.1



Transient response of the temperature-controlled system at the operating point

The transient response of the temperature-controlled system is shown as an

example. Please note that the same measurement taken on different systems can

lead to deviation. Such deviation is caused by component tolerances .The

measurement was made using the Compact Workstation level-controlled system and

recorded with FluidLab-PA and EasyportDA.

The jump is only shown for a temperature change of 5°K compared to the start

temperature, then the heater is switched off again.

The temperature-controlled system is a controlled system of the first order.

Solution for

Worksheet 5.1.1

Note:



• Which controller is suitable for which controlled system?

Permanent control deviation No permanent control deviation

P PD PI PID

Temperature Simple controlled

systems with

unsophisticated

requirements

Simple controlled

systems with

unsophisticated

requirements

Suitable Very suitable

Pressure Mostly unusable Mostly unusable Well suited.

Also I control-

lers for control-

led systems

with large delay

time

Suitable if

controlled

variable does

not pulsate too

much

Flow Unsuitable Unsuitable Usable, but I

controller alone

often better

Suitable

Level In the case of

short dead time

Suitable Suitable Very suitable

Transport Unsuitable

because of dead

time

Unsuitable Usable, but I

controller alone

often better

Has little

advantage over

PI

Selection of controller types for the most important controlled variables

Solution for

Worksheet 5.2.6



Controller type Controlled

system P PD PI PID

Pure dead

time

Unsuitable

because of dead

time

Unsuitable Usable, but I

controller

normally

sufficient

Has little

advantage over

PI

1st order with

short dead

time

Suitable if

control deviation

acceptable

Suitable if control

deviation

acceptable

Well suited Suitable

2nd order with

short dead

time

Control deviation

normally too

large for

required Xp

Control deviation

normally too large

for required Xp

Worse than PID Well suited

Higher order Unsuitable Unsuitable Worse than PID Well suited

Without

compensation

with delay

time

Suitable Suitable Suitable Very suitable



Procedure used in the Ziegler-Nichols method

Configure the controller as a P controller

Vary the amplification factor Kr until the controlled system approaches the limit of stability. (Until it

just starts to oscillate.)

Read the periodic time of an oscillation.

Use the Ziegler-Nichols table to calculate the necessary parameters for the controller.

Solution for

Worksheet 5.3.1

Documents

EMCS Technology Solutions V2