Mess- und Regeltechnik

Transcrição

Mess- und Regeltechnik
Mess- und Regeltechnik 2014
DRUCK
2
DRUCK
◦ Druck ist Kraft pro Fläche
◦ Einheit ist Pascal [Pa]= [N/m2]
◦ oft verwendet wird Bar oder Millibar
1[mbar] =1[hPa]
◦ Pound per square inch [psi]
1psi = 0,0689 bar
◦ Torr, mmWS, atm
3
Druckarten
4
Druckmessgeräte Manometer
Manometer mit Sperrflüssigkeit.
Offenes U-Rohr-Manometer
5
Manometer mit Sperrflüssigkeit. Geschlossenes URohr-Manometer für Unterdruck und Überdruck
6
Manometer federelastisch
Rohr-, Platten- u. Kapselfedermanometer
bis 1000 bar
bis 40 bar
bis 0,6 bar
7
Federelastischer Manometer mit Messumformer
8
Messbereiche: Pü :
0,1 ; 1 ; 1,6 ; 2,5 ; 4 ; 6 ; 10 ; 16 ; 25 ; 40 ; 60 ; 100 usw.
Genauigkeitsklassen:
0,1 ; 0,2 ; 0,6 ; 1 ; 1,6 ; 2,5 ; 4
als Messfehlergrenze in %
vom Messbereich
9
Druckmessumformer
Prinzip: Piezoresistiv (Si-Membran), induktiv, kapazitiv,
Dehnmessstreifen
10
Differenzdruck
Ausführung mit Sperrflüssigkeit, federelastisch,
pneumatisch, mechanisch u. elektrisch
11
Differenzdruck
12
Druckreduzierung Flaschendruckminderer
13
TEMPERATUR
14
Temperatur
Die Temperatur ist eine der am häufigsten
gemessenen physikalischen Größen.
Die Temperatur ist eine Größe, die den
Wärmezustand (= Maß für Energie) beschreibt.
Einheit ist Kelvin [K].
Oft verwendet wird Celsius [°C].
273,15 [K] ist 0 [°C]
15
Temperaturmessgeräte mechanisch
◦ Flüssigkeitsausdehnungs- u.
◦ FlüssigkeitsFeder Thermometer
Volumenänderung
bzw. Druckerhöhung
Hg: -35°C – +600°C
Alk: -70°C – +70°C
16
Temperaturmessgeräte mechanisch
◦ BimetallThermometer
-50°C - +500°C
+ Aufzeichnung
(Schreiber)
+ ZweipunktRegler
17
Temperaturmessgeräte elektrisch
◦ Elektrische Temperaturmessgeräte ergeben ein
von der Temperatur abhängiges elektrisches
Ausgangssignal
+ Signal kann zur Registrierung und als
Regelgröße verwendet werden
18
Temperaturmessgeräte elektrisch
◦ Widerstandsthermometer
Platindraht mit Nennwiderstand von 100 Ω Pt 100
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Widerstandsthermometer
20
+ sind die genauesten Thermometer
◦ -250°C bis + 650°C (850°C)
◦ Toleranzklassen A und B
+ Leitungen sind normale Kupferleitungen
Ausführung je nach Leitungskompensation
2, 3 oder 4 - Leitersysteme
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22
23
Thermoelement
•
•
•
•
24
Prinzip: Seebeck – Effekt (1822)
-270°C bis + 3000°C
8 genormte Thermopaare
Einteilung in Klassen 1 - 3
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Thermoelement: Farbcodierung
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Thermoelement
27
Vergleich: Thermoelement - Widerstandsthermometer
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PT100 mit Analogausgang
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DURCHFLUSS
30
Durchfluss
Mit Durchflussmessgeräten wird der augenblicklich
pro Zeiteinheit durch die Leitung fließende
Volumenstrom einer Flüssigkeit oder eines Gases
gemessen.
Durch
Multiplikation
mit
der
Betriebsdichte kann daraus der Massendurchfluss
berechnet werden.
Es gibt Durchflussmessgeräte nach verschiedenen
physikalischen Wirkungsmechanismen.
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Durchfluss
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Pitot- und Staurohr
Das Pitotrohr, ein hakenförmig
gekrümmtes offenes Rohr, wird gegen
die Strömung ausgerichtet und an
seiner Spitze ist der Gesamtdruck
wirksam. Über eine Schlauchleitung
wird es mit einem Druckmessgerät, z.B.
einem Schrägrohrmanometer,
verbunden.
33
Prandtlsches Staurohr
Mit dem äußeren Rohr wird der durch Einzelbohrungen oder einen
Ringspalt am Umfang (quer zur Strömung) gemessene statische
Druck zum zweiten Schlauchanschluss am hinteren Rohrende
geleitet.
Bei Anschluss beider Drücke an einem Schrägrohrmanometer
kommt die Differenz beider Drücke, der dynamische Druck, zur
Anzeige.
34
Turbinenradzähler
Dieses Gerät hat als Messglied ein
Turbinenrad. Der Gasstrom wird
von einem Verdrängerkörper in
einen Ringspalt geleitet und treibt
dort das Turbinenrad an. Es dreht
sich
mit
einer
zur
Strömungsgeschwindigkeit
des
Gases proportionalen Drehzahl.
Über eine Magnetkupplung oder
eine Induktionsspule wir die Anzahl
der
Turbinenradumdrehungen
ermittelt
und
daraus
das
durchgeflossene
Volumen
bestimmt.
35
WIRKDRUCK-DFM
Es kommt zum Auftreten des sog.
Wirkdrucks, aus dem sich über die
Durchflussgleichung der Durchfluss
berechnen lässt.
Unter Berücksichtigung der
Kontinuitätsgleichung und
Einführung des
Öffnungsverhältnisses m=A2/A1 (A1,
A2 sind die Strömungsquerschnitte)
ergibt sich für die Abhängigkeit des
Durchflusses vom Wirkdruck Dp
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QV = A1v = mA1
2 ∆p
ρ
⋅
1
1 − m2
WIRKDRUCK-DFM
Vor und hinter dem Drosselgerät darf die Rohrleitung keine
Querschnitts- oder Richtungsänderung aufweisen, um eine
exakte Messung zu gewährleisten.
Einlaufstrecke ≥10 D, Auslaufstrecke ≥5 D.
37
SCHWEBEKÖRPER-DFM
Auf den Schwebekörper wirken im wesentlichen drei Kräfte:
Die konstante Schwerkraft G
Die hydrostatische Auftriebskraft A, die gemäß dem Archimedischen Prinzip
bei konstanter Dichte des Messstoffes ebenfalls konstant ist
Die Kraft S, mit der die Strömung den Schwebekörper anhebt.
Schwebekörper-DFM sind auf die Messung bei niedrigen Drücken begrenzt.
Die VDI/VDE-Richtlinie 3513 beschreibt das Verfahren zur Berechnung der
Skalen.
38
SCHWEBEKÖRPER-DFM
Bei Änderung der Betriebstemperatur und des
Betriebsdruckes werden die Multiplikationsfaktoren
zur Korrektur nach folgenden Gleichungen
ermittelt:
Norm-bzw. Gewichtseinheiten
Betriebseinheiten
Kp = Korrekturfaktor für Druck
Kt = Korrekturfaktor für Temperatur
P1 = 1,013 bar + Kalibrierdruck in bar P2 = 1,013 bar + neuer Betreibsdruck in bar
T1 = 273 K + Kalibriertemperatur in °C T2 = 273 K + neue Betriebstemperatur in °C
39
SCHWEBEKÖRPER-DFM
Zudem ist bei Gasmessungen die
richtige Anordnung des Ventils (ein/auslassseitig) immer in
Zusammenhang mit dem
Kalibrierdruck zu betrachten.
Bedingt durch die Dichteänderung
des komprimierten Gases, ändern
sich die Auftriebskräfte am
Schwebekörper und somit natürlich
auch die Durchflussleistung
entsprechend. Damit der
Arbeitsdruck im Bereich des
Messrohres immer konstant bleibt, ist
das Einstellventil wie folgt
anzuordnen
40
MAGNETISCH-INDUKTIVE-DFM
Mit magnetisch-induktiven Durchflussmessern wird der Volumendurchfluss
von elektrisch leitfähigen Messstoffen gemessen. Ein elektrischer Leiter, hier
der elektrisch leitfähige Messstoff, bewegt sich durch ein Magnetfeld. In
diesem Messstoff wird eine Spannung U induziert, die direkt proportional von
der mittleren Fließgeschwindigkeit v abhängt.
Die magnetische Induktion B
(Stärke des Magnetfeldes) und
der Elektrodenabstand D
(Rohrnennweite) sind konstant.
U=K×B×v×D
K Gerätekonstante
B Stärke des Magnetfeldes
v mittlere Fließgeschwindigkeit
D Elektrodenabstand
41
ULTRASCHALL-DFM
1. Das Dopplerverfahren.
2. Das Laufzeit-Differenzverfahren.
42
THERMISCHE DFM
Das Herz eines thermischen MassenDurchflussmessers/-reglers ist der Sensor,
bestehend aus einem dünnen
Edelstahlrohr mit thermischen
Widerstandselementen. Ein Teil des
Gasstroms fließt durch diesen BypassSensor und wird durch Heizung 1 und 2
erwärmt. Bei Gasdurchfluss bedingt
durch den Wärmetransfer driften die
gemessenen Temperaturen T1 und T2
auseinander. Die Temperaturdifferenz ist
dem Massedurchfluss durch den Sensor
direkt proportional.
43
THERMISCHE DFM
44
GAS ANALYSIS
45
Gas Analysis
The analysis of gases in technical processes is a
fundamental requirement for an economical and
ecological utilisation in environmental and process
technology. One must differentiate between
quantitive and qualitative measurements.
Qualitative measurements define a single
component in a mixture.
Quantitive measurements define a concentration
of a component in a mixture.
In a technical process, the latter is used, as the
components are mostly known.
46
Gas Analysis Principles
The principles include:
◦ IR-Absorption
– NDIR (Non-Dispersive Infrared Spectrometer)
– FTIR (Fourier-Transformations-InfraredSpectrometer)
◦ Heat Conductivity
◦ Oxygen
– Electrochemical
– Paramagnetic
47
IR-Absorption
Aside from the Nobel gases (H2, N2, O2 etc.), all
gases can be measured. Typical examples are CO,
CO2, CH4 and CmHn (a dipole must be present,
which allows the molecule to swing).
The measurement principle is based on the
absorption of infrared radiation at various
wavelengths (4000–400 cm−1). Each gas has a
specific wavelength where absorption takes place.
The absorption is proportional to the concentration.
48
IR-Vibrations
49
NDIR-Spectrometer
An infrared source sends radiation via a splitter
through two chambers. One is a reference and the
other is the sample chamber. In the sample
chamber, a portion of the light is absorbed. Due to
the resulting temperature difference, a pressure
difference is created and therefore a change in
the flow. The flow is measured in the connecting
line and converted to an electrical signal.
The measuring chamber and cuvette length define
the measuring range (normally switchable 1:10).
Each gas requires an unique detector.
50
NDIR-Spectrometer
51
NDIR-Spectrometer
52
NDIR-Spectrometer
53
FTIR Spectrometer
This technique shines a beam containing many frequencies of light
at once, and measures how much of that beam is absorbed by the
sample. Next, the beam is modified to contain a different
combination of frequencies, giving a second data point. This
process is repeated many times. Afterwards, a computer takes all
these data and works backwards to infer what the absorption is at
each wavelength.
A broadband light source shines into a Michelson interferometer, a
certain configuration of mirrors, one of which is moved by a motor.
As this mirror moves, each wavelength of light in the beam is
periodically blocked, transmitted, blocked, transmitted, by the
interferometer, due to wave interference.
Different wavelengths are modulated at different rates, so that at
each moment, the beam coming out of the interferometer has a
different spectrum
54
FTIR Spectrometer
55
FTIR Spectrometer
• The cuvette „windows“ determine the spectral range
eg. KBr 400-4000cm-1.
• The spectral resolution is a question of price, 7 cm-1 is cheaper than 0.25
cm-1
• A better resolution will enable the separation of components at the same
wavelengths .
• A longer cuvette will increase the sensitivity of the FTIR. PPB is possible
with a 2.5m cuvette.
• So called “Open path” measurements can be made, eg. Between two
mountains over a town, to measure CO2.
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FTIR Spectrometer
Background
Interferogram
Scan
57
Heat Conductivity
Heat conductivity can be used to measure CH4,
CO2, H2, N2 , Argon and mixtures thereof.
The construction consists of four heated chambers.
Two for reference gas and two for the sample.
Different gases dissipate heat at different rates.
Therefore the heated conductors have different
temperatures and hence different electrical
resistance.
The conductors are connected to a wheatstone
bridge and a voltage is generated. The voltage is
proportional to the concentration
58
Heat Conductivity
59
Oxygen - Electrochemical
The electrochemical oxygen cell looks similar to a battery. A
current is generated which is directly proportional to the
concentration.
Reactions
• Cathode : O2 + 2H2O+ + 4e- -> 4OH• Anode :
2Pb + 4OH- -> 2PbO + 2H2O+ 4e• Total :
O2 + 2Pb -> 2PbO
In a serial based gas measurement system, the oxygen sensor
should be the last sensor in the chain!
The zero point is not calibrated, only the endpoint, using
surrounding air (20.95 Vol. %).
60
Oxygen - Electrochemical
61
Oxygen - Paramagnetic
Oxygen is one of the few gases with strong magnetic
susceptibility. The movement of the electrons within a
molecule generates magnetic moments.
The principle of the measurement is based on a sensor in
which a dumb-bell comprising two nitrogen filled spheres is
arranged in rotational symmetry within a magnetic field.
Oxygen entering the sensor is drawn into the magnetic field,
thereby strengthening the field. The nitrogen has the opposite
magnetic polarisation and therefore the dumb-bell rotates.
The degree of rotation is proportional to the concentration.
To reduce sensitivity to vibration, the rotation is measured
using light beam, a mirror and two photocells.
Benefits: No cross-sensitivity, rapid response. Long term
stability.
62
Oxygen - Paramagnetic
Permanent
Magnets
Nitrogen
Spheres
Mirror
63
Electrical
conductor
DATA ACQUISITION
64
Data Acquisition
“Data Acquisition” is the link from the ‘real world’ of
physical variables to your computer. Actual sensory
information such as sound, light, temperature,
vibration etc is converted by sensors to real time
signals that may be interpreted by the data
acquisition hardware.
◦ Analogue & Digital Signals
◦ Resolution
◦ Data Coding
◦ Interfaces
◦ Visualisation
65
Data Acquisition – Analogue & Digital Signals
A measurement e.g. Temperature is converted by a sensor
and transmitter into a signal that is proportional to the
temperature. Standard signals are:
◦
◦
◦
◦
0 - 20 mA
4 – 20 mA
0–5V
0 – 10 V
The electrical signal is converted to a digital signal for further
processing using an Analogue to Digital Converter (ADC).
The resolution of the ADC representing the signal is important!
66
Data Acquisition - Resolution
A 3-bit resolution of a sin wave
(with amplitude from 0 to 10)
would divide the signal into 23 or
8 levels giving a resolution of
only 1.25 per level, a very
inaccurate representation of the
wave. A 16-bit resolution would
mean that sin wave can be
represented by 216 levels (65536)
or effectively 0.00015 per level.
67
Data Acquisition – Resolution (Practical example)
An Eurotherm chart recorder reads a thermocouple and
converts the signal for further use on a PC. The recorder
cannot transmit a decimal point, therefore the values are
converted using a formula.
E.g. 16 bit ADC = 216 = 65536 & 20 °C
Output = resolution of DAQ x °C / Max. Temperature
= 65536 x 20 / 1100
= 1191.56 (sent as 1191)
PC converts back to a temperature: output x 1100 / 65536
= 19.99 °C
12 bit: 19.87 °C
Compare
8 bit: 17.18 °C
68
Data Acquisition – Data Coding
An interface can only transmit two states, LOW level (0) or
HIGH level (1). This represents a bit. The actual electrical value
for the high and low level is dependant on the interface itself.
+15V
Active state LOW (logical 0)
+3V
-3V
Non Active state HIGH (logical 1)
-15V
69
The signal level for the
RS232C interface is
shown left. The area
between +3V and –3V
is not defined.
Data Acquisition – Data Coding
In practice, interfaces never send single bits of
information, the bits are grouped into blocks of
eight and are called bytes.
The 128 standard characters (ASCII) require only 7
bits but the 8th bit is used to allow the use of 256
characters and the extended codes.
To increase accuracy, integer numbers (0 – 65536)
are sent as 2 bytes or a word. Floating point
numbers in the range 1.0E±38 are sent as 4 bytes.
70
Data Acquisition – Interfaces
Serial & Parallel
Data is normally transferred in a bus system as a serial
transmission with each bit being transmitted sequentially over
for example a 2-wire cable. In some cases, a parallel
transmission is used as it has a higher transmission rate but
only works over short distances due to the increased
sensitivity to interference. The RS232, RS422 and RS485
interfaces all function as serial transmission methods with for
example the MODbus protocol.
RS232: 2-Wire cross over + Ground.
RS422: 4-Wire cross over. TxD & RxD split into a “+” positive
and “- “ negative.
RS485: 2-Wire with state switching (master/slave).
71
Serial & Parallel
RS232 No Bus capability. Can only connect two devices.
RS422 Bus capability up to 32 stations. Max 1200m apart.
Distance can be increased by using Repeaters. Less
sensitive to interference than the RS232 as the
measured
signal is always the difference between
the two signals.
E.g. TxD+ has +5V and TxD- has –5V, this corresponds
to logical “0” and the reverse as logical “1”.
RS485 Same capability as for RS422. Interface available for
PC otherwise bus converter required.
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Interface Speeds.
Serial 1 bit transfer
Parallel 8 bit (150kB/s)
USB 2.0
USB 3.0
Firewire (i-Link, 1394)
Ethernet
WLAN
73
up to 115200 bits/s
~10 Mbits/s
480 Mbits/s
4 Gbits/s
12 Mbits/s
1 Gbit/s
600 Mbits/s
Data Acquisition – Visualisation
Visualisation software is the last part of data acquisition. Most
hardware requires a driver to access the registers of the DAQ
hardware. A common example is the Labview software from
National Instruments.
Labview stands for Laboratory Virtual Instrumentation
Engineering Workbench
First development in 1986 for Macintosh Computers.
Comprises a graphical user interface or front panel (GUI), a
block diagram and a connector diagram.
Program is compiled into machine code.
74
75
From the same company, the SCADA software
Lookout is also available.
“National Instruments Lookout is an easy-to-use
Web-enabled human machine interface (HMI) and
supervisory control and data acquisition (SCADA)
software system for demanding manufacturing
and process control applications. With Lookout,
developing your HMI/SCADA application takes less
time, delivering substantial savings on overall
project costs.”
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77
Problem: No driver for my software / hardware combination
Solution: OPC-Server
OLE for Process Control (OPC) is a standard used to bridge
windows based programs and process control hardware from
different manufacturers. Object Linking and Embedding (OLE)
is a distributed object system and protocol developed by
Microsoft. OLE 1.0 was the origin of Dynamic Data Exchange
(DDE) which allows two running programs to exchange data
and is used today. OLE 2.0 has been further developed and is
now called ActiveX.
For the exercise, Lookout from National Instruments will be used to
communicate with a data acquisition system from Eurotherm via an
OPC-Server, as a direct communication protocol is not available.
78
Data Acquisition – References
[1] “Digital Interfaces and Bus Systems, Fundamentals and
practical advice for the connection of field devices to
MODbus, PROFIBUS-DP, ETHERNET, CANopen and HART®”;
Manfred Schleicher; ISBN-13: 978-3-935742-03-0 (as PDF-File
from www.jumo.at)
[2] Wikipedia
[3] “A basic guide to data acquisition”; Blue Chip
Technology; www.bluechiptechnology.co.uk
[4] Lookout Reference Manual, National Instruments
www.ni.com.
79
BUS SYSTEMS
80
In computer terminology, the bus system is the term for the bidirectional data communication system that carries all
electrical information between the central processing unit
(CPU) and the other devices in the system e.g. random
access memory (RAM), PCI expansion slots, hard-disks etc
and is commonly called the front side bus (FSB).
In industry, the equivalent would be the “black box” between
individual sensors (for example) and the computer control
system. This black box interface can take various forms:
◦ data logger
◦ a SPS-System (SpeicherProgrammierbare Steuerung –
Memory programmable control)
◦ PC-Interface card or
◦ a simple amplifier coupled with interface port.
81
Bus Systems
Usually, the interface can be found locally near the sensor
group, with multiple interfaces being connected via a 2-wire
cable to a central control system or PC. All components are
therefore connected and form together the bus system. An
access procedure regulates which interfaces talks on the bus
and when.
82
Bus Systems – Transmission Properties
Master / Slave Procedure
Master calls slaves consecutively, slave listens, answers and
confirms.
Time for one loop (all slaves) is the Bus Cycle Time.
PROFIBUS-DP in milliseconds, MODBus in seconds.
83
Bus Systems – Transmission Properties
Token-Passing Procedure
More than one Master.
Master with the token can talk to the slaves.
An example of this system is PROFIBUS-DP.
84
Bus Systems – Collision
◦ If a system operates with the CSMA procedure (Carrier
Sense Multiple Access), then all stations on the bus have
equal rights.
◦ Any station can start transmitting on its own accord. The
principle is, that every station checks whether another
station is transmitting at the moment, before it starts
transmitting.
◦ Problems arise if two stations start transmitting
simultaneously.
◦ There are various possibilities for dealing with this situation,
which is known as a collision:
85
CSMA-CD
When using the CSMA-CD access procedure (Carrier Sense
Multiple Access Collision Detection), if two stations transmit
simultaneously, then the message will be destroyed. The
stations recognise the simultaneous transmission, and repeat
the transmission on a random basis. If another collision occurs,
there will be a fresh transmission etc.
ETHERNET, for instance, works on this principle.
86
CSMA-CA
When using the CSMA-CA procedure (Carrier Sense Multiple
Access Collision Avoid), the station that is transmitting the
message with a lower priority will disconnect from the bus.
Thanks to the arrangement of the protocol and the electrical
characteristics of the interface, the higher-priority message
will obtain access and be transmitted without disturbance.
87
Bus Systems – Transmission Media
◦ Co-Axial and optical fibre cables can be used.
◦ More common, shielded, twisted pair.
◦ Important: Inductance and Capacitance should be low to
avoid signal loss.
◦ Typical capacitance <30pF/meter.
◦ Increasing cable length = increasing signal loss
◦ Therefore decrease transmission rate (Baud Rate) to
compensate!
88
Bus Systems – Transmission Media
E.g. RS485 interface can transmit up to 12 Mbps which
decreases rapidly.
Length (m)
100
200
400
1000
1200
Baud Rate
(kbps)
12000
1500
500
187.5
9.6
A further point is the so called termination resistor. If the ends of the
cable on the bus were open, the signals would be reflected. The higher
the baud rate, the worse this effect will be. A termination resistor at each
end minimises this problem.
89
Bus Systems – Transmission Protocol
The transmission protocol is the common language between
the master and slave(s). Standard protocols include:
◦
◦
◦
◦
◦
90
MODBus
ProfiBus
Ethernet
Can
Hart
Bus Systems – Transmission Protocol
Manufacturer
MODbus
PROFIBUS-DP
Gould-Modicon
Siemens, Klöckner Möller,
ETHERNET
CANopen
HART
Bosch and Intel
Rosemount Inc.
Bosch etc.
Access
Master/Slave
Master/Slave
CSMA-CD
CSMA-CA
Master/Slave
Medium
unrestricted
2-wire or optical fibre
2-wire cable
2-wire cable
2-wire cable
Baud rate
Up to 187.5 kbps
9600 bps to 12 Mbps
100Mbps
50kbps to 1Mbps
1200bps
Bus expansion
Up to 1200m/segment
1200m/segment
Max. 100m between two
Up to 5000m
Up to 2000m
www.can-cia.de
www.hartcomm.org
points
Hyperlink
91
www.modbus.org
www.profibus.com
www.iano-eu.com
Bus Systems – MODBus
◦ Developed in 1979 by Gould-Modicon, America.
◦ Uses RS232 or RS485
◦ Baud Rate, Parity Check & Stop Bits must be same for all
stations.
◦ Master / Slave procedure. Each with unique address!
◦ Uses function codes:
–
–
–
–
–
–
–
92
Read N bits:
Read N words:
Write a bit:
Write a word:
Fast read of status:
Diagnostic:
Write N words:
Code 01 or 02
Code 03 or 04
Code 05
Code 06
Code 07
Code 08
Code 16
Example with Eurotherm 4180M chart recorder.
For a thermocouple, Type K, Range 0 – 1100°C
M = measured temperature in °C ( 20°C = 1.1mV)
R = resolution of DAQ ( 16 bit = 216 = 65536)
Max = maximum temperature in °C (1100°C = 65mV )
Raw output value from recorder
= R x M /Max
= 1191
93
Example with Eurotherm 4180M chart recorder.
If this thermocouple is connected to channel 1 on the
recorder, the command to read this channel in would be:
Modbus1.40001 x 1100 / 65536
Where:
Modbus1
1100
65536
40001
94
= The name of the protocol driver
= The maximum measured value of the TC
= The resolution of the recorder.
= Code (0)4, read input register followed by
0001, address of channel 1
Bus Systems – Profibus DP
PROcess Field Bus
◦ Network comprising Master (PC or PLC [Programmable
Logic Controller] & Slave devices. 2-wire with terminators.
◦ Bi-Directional
◦ Each device has a unique address.
◦ User defines – Device & Information in device (GSD
Database)
◦ Network configuration file is generated.
◦ Uses a polling cycle (similar to SPS).
◦ Very fast – milliseconds!
◦ Device description file (GSD) describes functionality of
device, baud rates, inputs & outputs etc.
95
Bus Systems – Profibus DP
96
Bus Systems – HART
Highway Addressable
Remote Transducer.
◦ The
HART
Protocol
makes use of the Bell 202
Frequency Shift Keying
(FSK)
standard
to
superimpose
digital
communication signals
at a low level on top of
the 4-20mA
97
Bus Systems – HART
Global standard for sending and receiving digital information
across analog wires between smart devices and control or
monitoring system
Communicates at 1200 bps without interrupting the 4-20mA
signal and allows a host application (master) to get two or
more digital updates per second from a smart field device.
As the digital FSK signal is phase continuous, there is no
interference with the 4-20mA signal.
Simultaneous transfer of the primary analog measurement
signal & device information in the digital signal.
Low cost, easy to use and configure.
Example: Caller ID on landline!
98
Bus Systems – CAN bus
Controller Area Network
A vehicle bus standard designed to allow microcontrollers
and devices to communicate with each other within a
vehicle without a host computer.
CAN bus is a message-based protocol, designed specifically
for automotive applications
CAN is a multi-master broadcast serial bus standard for
connecting electronic control units (ECUs).
Each ECU has a proirity.
99
VERDRAHTUNG
100
Verdrahtung
Unter „Verdrahtung“ versteht man alles, was
innerhalb eines Schaltschranks, innerhalb eines
Verteilerschrankes oder dergleichen für eine
Steuerung oder Regelung, egal welcher Art,
elektrischerseits benötigt wird. Dabei spielt die
Größe des Schrankes keine Rolle. Wichtig ist in
erster Linie, dass gemäß der Norm EN 60204 (alte
VDE 0113) mehr als zwei Komponenten mit Drähten
oder Leitungen verbunden werden. Komponenten
sind Schalter, Taster, Schütze, Relais, SPS,
Frequenzumrichter, Klemmen, usw., die für eine
Steuerung oder Regelung benötigt werden.
101
Ein Schaltschrank beherbergt die elektrischen und
elektronischen Komponenten einer
verfahrenstechnischen Anlage, einer
Werkzeugmaschine oder Fertigungseinrichtung, die
sich nicht direkt in der Maschine (z. B. Sensoren)
befinden.
Im einfachsten Fall enthält er nur Klemmen zum
übersichtlichen elektrischen Verbinden
verschiedener Komponenten einer Anlage
(Klemmkasten, Verteilerkasten). Bei einem
geschlossenen Schrank ist die zufällige und
unbeabsichtigte Berührung spannungsführender
Bauteile ausgeschlossen.
102
Kabelkanal
Datenerfassung
Netzwerk
24V Stromversorgung
Leistungsschutzschalter
& Relais
Reihenklemmen
103
24V Stromversorgung
24V Reihenklemmen
Klemmenbrücken
104
~230V Versorgung
105
=24V geschaltete Versorgung
L, N & PE
~230V Ausgänge
~400V Versorgung
106
Reihenklemmen
Bezeichnung (X4)
Sicherheitsklemme
Geschaltete 24V Ausgänge
107
Trennplatte
Durchgangs-Reihenklemmen
Weidmüller WDU2.5 (800V, 32A)
Weidmüller WQV 2.5/10
Reihenklemme Schutzleiter WPE 2,5
Hutschiene
108
Leitungsschutzschalter MCB 1P+N 6 A
Charakteristik Typ C
Halbleiterrelais 6 A 280 V eff.
Steuerspannung 24V
109
1 mm² Einzeladerleitung,
AWG 18, 600 V, PVC,
Nennstrom 17A
110
Leitungsquerschnitt mm2
Max. Strom A
0,75
6
1,0
10
1,5
13
2,5
16
4,0
25
Magnetventil Öffner, 24 V, 1 Zoll,
Port DN25, Leistung 29W
Verhalten:
NC – Normally Closed
NO – Normally Open
VORSICHT:
P=I*U
I=P/U
I = 29 / 24 = 1,21 A
111
Merken: 3 x 16A Versorgung!
Hauptschalter
Versorgung
112
24V Versorgung
Vorsicht 2 x 10A Netzteile auf L3!
113
Vorsicht 2 x 10A Netzteile!
P=I*U
P = (10 + 10 ) * 24 = 480 Watt
P = I * U folgt I = P / U
I = 480W / 230V = 2,08A !!
114
Auslegung von 24V Netzteile:
Leistung von alle Abnehmer summieren
I = Gesamtleistung / 24
Beispiel: 10 Stück Magnetventile je 30W
10 x 30 = 300W / 24V = 12,5A
Vorsicht: Wirkungsgrad
300W mit WG 80%
€300 !
115
300/0,8 = 375W !
116
24V Magnetventil
Schalter od.
Relais
24V Versorgung
117
Cerabar S PMC71 Prozessdrucktransmitter
3 & 4 Erdungsklemme
118
6 & 7 Versorgung
Drucktransmitter
Multimeter od.
Datenerfassung
24V Versorgung
2 Drahtsystem
119
Multimeter od.
Datenerfassung
Drucktransmitter
24V Versorgung
120
Massendurchflussmesser MFM
DAQ
Datenerfassung
4 Drahtsystem
121
Massendurchflusscontroller MFC
DAQ
24V
122
Sollwertgeber
zB. Poti.
4 – 20 mA
100 Ohm
Signalumwandlung mA -> V mittels „Shunt“ [ U=R*I]
0,4 – 2 V
• Wiederstand kann optimal
ausgewählt abhängig von DAQ
100 Ohm= 2V, 500 Ohm = 10V.
• Wiederstand muss sehr Genau
sein (100±0,1 Ohm)!
123
EUROTHERM 2500
124
125
Unit comprises Module + Terminal
Terminal determines input signal.
126
IOC (CPU) Terminal
127
Input terminal for
• Temperature
• Voltage
• Current (with resistor)
128
Output Terminal for
• Voltage
• Current
129
Terminal for 4 Channel Relay Output
A1
B1
24V +
0V
130
Magnetic Valve
Example connection for pressure sensor
A1
C1
24V +
0V
131
Pressure
Transmitter
iTools Configuration Software
132
Connect PC and DAQ with appropriate cable. Start iTools software. Start Abfrage
2500 found
133
Turn on config mode
Relays and outputs are not active in edit mode!
134
Check each module found is the correct module.
135
Example: 4-20mA with 5 ohm Shunt scaled to 0-100 bar
136
Read „val“ with OPC server or with Modbus address 5207
137
Configuration for Relay channel. Output 0 or 1 to „val“ to open or close.
138
Complete example to read a temperature using
Eurotherm OPC-Server.
139
Configure module with iTools. E:g. Module 01: AI2
140
Channel 1 configured for Thermocouple Type K. Temperature can be seen.
141
When configuration is finished, turn off edit (Zugriff).
Start OPC-Server, DAQ should be automatically found, if not, ask!
Activate Monitor.
142
In Lookout software, create driver object: OPCClient.
143
Create new object: Create, Object, Display, Gauge, to read Channel 1, „Val“.
144
Format gauge display to digital
145
Data is displayed real-time!
146
Complete example to control a relay using
Eurotherm OPC-Server.
147
In your project, add a driver object – OPC Client.
148
Select the Eurotherm server.
149
Create a controlling object eg. A switch.
150
Select from the menu: Edit connections in edit. Select your
process followed by OPC client1.
151
Select COM1 where the DAQ is connected (Top left).
152
Select ID255-2580 this is the DAQ.
153
Select IO.
Select the correct module AND channel.
154
Here we use module 4, channel 1
155
Highlight „Val“ and press select.
Select bottom left, your process.
156
Highlight your controlling object and
press paste.
In the middle you see the connection. Press accept.
157
After Accept, you see, top right, the new connection. Press quit. Try the switch!
What have you just done?
You have said that the value
of module 4 (Relay module),
channel 1 takes its value
from the value of the switch
(0 or 1). This value is
continuously sent to the
DAQ.
Think back. You have done
this before with the logger
panel!
158

Mess- und Regeltechnik

Transcrição

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