1. BASICS OF INSTRUMENTATION
Presented by
BHAVIRI THAVITI RAJU M.Tech,
Assistant Professor
DEPARTMENT OF AUTOMOBILE ENGINEERING
VISAKHA INSTITUTE OF ENGINEERING & TECHNOLOGY

2. BASICS What is Instrumentation? Basic Terminologies
Process & its Control
Field Instruments & its principles
Valves & its working

3. What is Instrumentation?
Instrumentation is about measurement and control.
Instrumentation engineering is the engineering specialization focused on the design and configuration of process systems.
Instruments are devices which are used in measuring attributes of process systems.

4. Basic Terminologies • Process:
Series of continuous or regularly recurring steps or actions intended to achieve a predetermined result, as in heat treating metal, or manufacturing acid. •
Transducer(sensor):
Element which converts one form of Energy to Other form. •
Primary Transducer:
Transducer which converts the Process parameter to a form readable by Secondary Transducer.
Eg: Orifice plate •
Secondary Transducer:
Transducer or transmitter which responds to a measured variable and converts it to a standardized transmission signal which is a function only of the measurement.
Eg: DP Transmitter

5. •
Signal:
The signal is the event or phenomenon that conveys data from one point to another. •
Loop:
A Loop is a combination of one or more interconnected instruments arranged to measure a process variable. It shall comprises the whole chain from Primary element to Correcting Element. •
Controller:
A device that operates automatically by use of some established algorithm to regulate process variable(PV) according to the set point(SV). The controller input receives information about the status of the process variable and then provides an appropriate output signal(MV-manipulated variable) to the final control element(eg-valves etc.,).

6. Interlock:
It refers to the set of plant conditions(eg. Level of a tank, temp of furnace, position of furnace or a valve, flow of a fluid, etc) which are to be satisfied before operating(starting, stopping, opening ,closing ,etc)of any instrument or equipment.
ANALYSER:
Monitor pollutant gas emissions from industrial processes.
Gas analyzer is a gas comparator providing high linearity of signal transformation function.
WEIGHFEEDER:
Controller multiplies the signal from the load cell(belt load,kg/m) with that from the speed transducer(belt speed,m/s) to get the feed rate.
The controller then either changes the belt speed or belt load to get the set feed rate.

7. CONVEYOR:
Conveyors are used as components in automated distribution and warehousing. A belt conveyor consists of two or more pulleys, with a continuous loop of material - the conveyor belt - that rotates about them. One or both of the pulleys are powered, moving the belt and the material on the belt forward. The powered pulley is called the drive pulley while the unpowered pulley is called the idler.
BELTWEIGHER:
Material flowing over the belt may be weighed in transit using a beltweigher.A belweigher or belt weigher is a piece of industrial control equipment used to gauge the mass or flow rate of material travelling over a conveyor belt.

8. Process & its Control Process Parameters: –
Pressure Level Temperature Flow

9. Pressure Measurement • PRESSURE
A force applied to or distributed over a surface. The pressure (P) of a force (F) distributed over an area(A) is defined as :
P = F / A
Standard Unit of Pressure is Pascal
Other units of pressure are
psi kg/cm 2 bar
atmosphere torr
1 Pa = 1 N/m2

10. Pressure Measurement Primary Pressure Measuring Devices:
Diaphragm
Bellows
Manometer
Pressure measurements can be divided into three different categories:
absolute pressure
gauge pressure and
differential pressure

11. GAUGE PRESSURE
Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.
In measurements a gauge is used to record the pressure difference between the system and the atmospheric pressure. This is called gauge pressure and can be stated by the following equation:
Pg=Pa+Po
where
Pg= gauge pressure
Po = atmospheric pressure
If the pressure of a system is below atmospheric, it is called vacuum pressure.
When pressure is measured by a gauge, the quantity obtained usually excludes the
ambient atmospheric pressure and is therefore called overpressure,
Poverpressure = Pgauge

12. DIFFERENTIAL PRESSURE
ABSOLUTE PRESSURE
If atmospheric pressure is included, then the resulting pressure is called absolute pressure
Pabsolute = Patmospheric + Pgauge
The absolute pressure is measured relative to the absolute zero pressure - the pressure that would occur at absolute vacuum.
P= Pg+ Po
P=absolute pressure, Pg=gauge pressure, Po=atmospheric pressure.
DIFFERENTIAL PRESSURE
Differential pressure is the difference in pressure between two points.

13. ATMOSPHERIC PRESSURE STANDARD ATMOSPHERIC PRESSURE :
The atmospheric pressure is the pressure in the surrounding air at or "close" to the surface of the earth.
The atmospheric pressure varies with temperature and altitude above sea level.
Atmospheric pressure is the pressure exerted at the surface of a body by a column of air in an atmosphere.
1 atmosphere on Earth = 760 millimeters of mercury ( 760 Torr) and 101, 325 Pascals.
STANDARD ATMOSPHERIC PRESSURE :
The Standard Atmospheric Pressure ( atm) is used as a reference for gas densities and volumes.
The Standard Atmospheric Pressure is defined at sea- level at 273 oK (0 oC) and is bar or Pa ( absolute). The temperature of 293 oK ( 20oC) is also used.

14. Types of Pressure Measuring Devices
Manometer
Bourdan Gauge

15. Contd..
Peizo Electric
Strain Gage Types
Capacitive
LVDT

16. Level Measurement •
Some of the most commonly used liquid-level measurement methods are:
RF capacitance
Conductance (conductivity)
Hydrostatic head/tank gauging
Radar
Ultrasonic

17. Level Measurement
Level Measurement using Pressure Transmitter
P = ρgh

18. Open Tank
Closed Tank

19. RF Capacitance
Conductive Type

20. Hydrostatic Head

21. Ultrasonic Type
RADAR Type

22. Flow Measurement
Principle:
– Flow is measured by measuring velocity through a known area.with this indirect method,the flow measured is the volume flow rate Q .
Q = A x V
Where A is the cross sectional area of the pipe
V is the fluid velocity
Unit of low is m3/hr or litres/hr

23. Flow Measurements Types: –
Head Type Flowmeters Mechanical Flowmeters Electronic Flowmeters Mass Flowmeters

24. Different Type of Head Type Flowmeters
Orifice Plate
Venturi
Flow Nozzle
Pitot Tube
Elbow

25. Orifice Basic Equation :V=k*(h/D)0.5 •
Service: Clean Liquids, Gases Steam,(no slurries or corrosive) Scale: Square Root
Accuracy: 1% Full Scale Permanent Pressure Loss: High
Cost: Low
Basic Equation :V=k*(h/D)0.5

26. Venturi •
Service: Clean Liquids, Gases Steam Slurries and Dirty Fluids Scale: Square Root
Accuracy: 1% Full Scale
Rangability: 3:1
Permanent Pressure Loss: Low Cost: High

27. Variable Area Meters

28. Mechanical Flowmeters

29. Electronic Flowmeters

30. Vortex Flowmeters

32. Ultrasonic Flowmeters

33. Temperature Measurement•
Temperature:
– Webster’s defines temperature as “the degree of hotness or coldness measured on a definite scale.
Various units of temperature are related as C = 5/9 (F – 32)
F = 9/5 (C ) K = C
R = F

34. Temperature Measurement
Types of Temp Measurement:
RTD
Thermocouple
Thermistor
Thermopile
Pyrometer

35. Temperature terminology
Temperature Control Loop
Temperature Loop Issues: –
Fluid response slowly to change in input heat Requires advanced control strategies
Feedforward Control
Load Disturbance
TIC
Cold Water I/ P TT
Steam
Hot
Water 35

36. Temperature Measurement Technology
Change in RESISTANCE with response to change in TEMPERATURE
Thermistors
RTD (discussed later)
Example: • •
Thermistors
Semi-conductors made from specific mixtures of pure oxides of nickel, manganese, copper, cobalt, and other metals sintered at very high temperature.
Used with Wheatstone Bridge which amplifies small change in resistance - in a simple circuit with a battery and a micro-ammeter. •
Stability
Linearity
Slope of Output -
Moderate
Poor (Logarithmic)
Negative 36

37. Temperature Sensors – Resistance Temperature Detector What is an RTD ?
RTDs
What is an RTD ?
– Resistance Temperature Detector
Operation depends on inherent characteristic of metal
(Platinum usually): electrical resistance to current flow
changes
when a metal undergoes a change in temperature.
If we can measure the resistance in the metal, we know
the temperature!
Platinum resistance changes with temperature
Thin-film sensing element
Rosemount’s
Wire-wound sensing element
Rosemount’s
Series 68, 58
Series 78, 88 Two common types of RTD elements:Series 65 37

38. Temperature Sensors How does a RTD works?
RTDs
How does a RTD works?
Resistance changes are Repeatable
The resistance changes of the platinum wiring can be approximated by an ideal curve -- the IEC 751
350
International Resistance vs. Temperature Chart:
Resistance (Ohms)
300
IEC 751
250 oC
Ohms
100.00 20
107.79 30
111.67
200
150
100 50
-400
-200
Temperature (oC)
800
IEC 751
IEC 751 Constants are :- A = , B = x 10 -7, If t>=0°C, C=0, If t<0, C = x
RT = R0 [1 + At + Bt2 + C(t-100)t3] =
Example: 38

39. “40 millivolts!,” Tommy Seebeck yelled in a heated debate.
Temperature Sensors
Thermocouples
What is a Thermocouple ?
Two dissimilar metals joined at a “Hot” junction
The wires are connected to an instrument (voltmeter) that measures the potential created by the temperature
difference between the two ends.
Process Temperature
“40 millivolts!,” Tommy Seebeck yelled in a heated debate.
Hot junction
Cold junction + DT
M V -
The junction of two dissimilar metals creates a small voltage output proportional to temperature! 39

40. Temperature Sensors How does a Thermocouple work ?
Thermocouples
How does a Thermocouple work ?
– The measured voltage is proportional to the temperature
difference between the hot and cold junction! (T2 - T1) =T.
Hot junction
Cold junction
Measurement +
 T MV
Reference Junction T1
Junction T2
Heat -
Thermoelectric Voltage vs. Temperature Chart: 80
Voltage (mV) 60 oC
Millivolts
0.000 10
0.591 20
1.192
IEC 584 40 20
TYPE E THERMOCOUPLE
-500
500
1000
-20
Temperature (oC) 40

41. Temperature Sensors + - + - + - – Iron / Constantan
Thermocouples
Types of Thermocouple
Type J
– Iron / Constantan •
White, Red 0 to 760 °C
Least Expensive
Type T
– Copper / Constantan
+ -
Type K
– Chromel / Alumel
Blue, Red
-180 to 371 °C
Highly resistant to corrosion from moisture
+ -
Yellow, Red 0 to 1150 °C
Most Linear
+ - 41

42. Temperature Sensors Why choose RTD over Thermocouple ? Comparison
Better Accuracy & Repeatability
RTD signal less susceptible to noise
Better linearity
RTD can be “matched” to transmitter (Interchangeability error eliminated)
CJC error inherent with T/C’s; RTD’s lead wire resistance errors can be eliminated
Better Stability
T/C drift is erratic and unpredictable; RTD’s drift predictably
T/C’s cannot be re-calibrated
Greater Flexibility
Special extension wires not needed
Don’t need to be careful with cold junctions 42

43. Temperature Sensors Why choose thermocouple over RTD ? Comparison •
Applications for Higher Temperatures
Above 1100°F Lower Element Cost
Cost is the same when considering temperature point performance requirements
Faster response time
Insignificant compared to response time for T-Well and process
Perceived as more rugged
Rosemount construction techniques produce extremely rugged RTD • • • 43

44. Temperature Sensors Comparison
RANGE
OFFER
-200 to 500º C
500 to 1100º C
>1100º C
RTD
Thermocouple Type K
Special Thermocouple R, S or B 44

45. Sensor accessories Thermowells
What is a thermowell (T-well) ?
A unit that protects a sensor from process flow, pressure, vibrations, and corrosion
Allows for sensor removal without process shutdown
Slows response time (by 5 times)
Why are there different material types ?
To handle different corrosive environments
To handle different temperature and pressure limits 45

46. Control Valves •
The control valve manipulates a flowing fluid, such as gas, steam, water, or chemical compounds, to compensate for the load disturbance and keep the regulated process variable as close as possible to the desired set point.
The control valve regulates the rate of fluid flow as the position of the valve plug or disk is changed by force from the actuator.
Control valves are valves used within industrial plants and elsewhere to control operating conditions such as temperature, pressure ,flow, and liquid level by fully or partially opening or closing in response to signals received from controllers that compare a "set point" to a "process variable" whose value is provided by sensors that monitor changes in such conditions.
The opening or closing of control valves is done by means of electrical, hydraulic or pneumatic systems. • • •

47. CONTROL VALVES:
They are basically pneumatically operated valves which require around 4 to 5 kg/cm2 of air pressure to operate the valve.
Pneumatic signal
CONTROL VALVE
I / P Converter
POSITIONER
CURRENT
SUPPLY AIR
SUPPLY AIR

48. Control Valve Types

52. Valve Body Types Diff. types of Valve Body: Butterfly Valve
Globe Valve
Ball Valve
Plug type Valve
Needle Valve

53. Positioner & its accessories•
Pneumatically operated valves depend on a positioner to take an input signal from a process controller and convert it to valve travel.
A pneumatic signal (usually 3-15 psig) is supplied to the positioner. The positioner translates this to a required valve position and supplies the valve actuator with the required air pressure to move the valve to the correct position.
Analog I/P Positioner—This positioner performs the same function as the one above, but uses electrical current (usually mA) instead of air as the input signal. • •

55. Automation (ancient Greek: = self dictated), roboticization or industrial automation or numerical control is the use of control systems such as computers to control industrial machinery and processes, replacing human operators.
The most commonly used automation systems are :
DCS - Distributed Control System
PLC - Programmable Logic Controller
SCADA – Supervisory Control And Data Acquisition System

56. DCS •
Distributed control system (DCS) refers to a control system usually of a manufacturing system, process or any kind of dynamic system, in which the controller elements are not central in location (like the brain) but are distributed throughout the system with each component sub-system controlled by one or more controllers. The entire system of controllers are connected by a network for communication and monitoring.
DCS is a very broad term used in a variety of industries, to monitor and control distributed equipment.
A DCS typically uses computers (usually custom designed processors) as controllers and uses both proprietary interconnections and protocols for communication. Input & output modules form component parts of the DCS. The processor receives information from input modules and sends information to output modules. The input modules receive information from input instruments in the process (a.k.a. field) and output modules transmit instructions to the output instruments in the field. Computer buses or electrical buses connect the processor and modules through multiplexers/demultiplexers. Buses also connect the distributed controllers with the central controller and finally to the
Human-Machine Interface (HMI) or control consoles. • •

57. ARCHITECTURE OF DCS Operator Workstation 1 Operator Workstation 2
Database
Controller 1
Controller 2
Controller 3
Controller 4
Input Module
Output Module
Input Module
Output Module
Input Module
Output Module
Input Module
Output Module
Sensor 1
Actuator 1
Sensor 2
Actuator 2
Sensor 3
Actuator 3
Sensor 4
Actuator 4

58. HIS HIS FCS FCS DCS : BASIC CONFIGURATION BCV MOPL MFCD ETHERNET
ENG STATION
V NET
V NET
V NET
BCV
FCS
FCS
RL BUS
RIO BUS
MOPL
MFCD
NIU
NIU
MAR
FIELD
MAR
MAR
FIELD INSTRUMENTS
INSTRUMENTS
JB 2
JB 1
JB 3

59. BASIC TERMINOLOGIES OF DCS
HIS:
Human Interface Station
The HIS is mainly used for operation and monitoring-it displays process variables,control parameters and alarms necessary for users to quickly grasp the operating status of the plant.
NIU: Node Interface Unit
These are remote I/O units which all the Instruments are connected.these units in turn are connected to FCS through RIO bus.
FCS:
Field Control Station
It is the main control unit which controls the plant.there can be more than one FCS which then communicate with each other and also communicate with the HIS from where the Operator is operating.
Vnet:
The Vnet real time control system BUS links station such as FCS,HIS,BCV andCGW.
ETHERNET:
Ethernet is used to link HIS,ENG and supervisory systems.it is also used for transferring data files to supervisory computers and for HIS data equalization.
RL Bus: This a control system BUS(communication link) which connects Field control units,operators stations.
CGW: Communication Gateway
This unit links the Vnet control system BUS to an ETHERNET BUS
BCV: Bus Converter
The communication bus of one version of DCS may not communicate with the newer versions so BUS CONVERTER is used to convert the BUS to suitable mode.
In our plant our existing RL BUS is converted to newer system bus Vnet by the Bus Converter kept in Engineering room near central control room.

60. Programmable Logic Controller (PLC)
Programmable Logic Controller (PLC) is a microprocessor based system that uses programmable memory to store instructions and implement functions such as logic, sequencing, timing, counting and arithmetic in order to control machines and processes.
Unlike Personal Computer, PLC does not contain peripherals, such as display or keyboard, that allow user to directly interact with PLC. In order to facilitate interaction, separate computer is provided, normally taking form of a standard PC. Through this external computer, operator can re-program PLC, provide set-points and view trends of process variables that are controlled and manipulated by PLC.
External Computer
PLC
Actuator
Process
Sensor

61. Programmable Logic Controller Architecture
PLC
Power Supply
Microprocessor + Memory
Operator Workstation
Communication Module
Discrete Sensor
Discrete Input (DI) Module
Analogue Input (AI) Module
Analogue Sensor
Discrete Actuator
Discrete Output (DO) Module
Analogue Actuator
Analogue Output (AO) Module

62. Programmable Logic Controller Architecture
External Computer
Communication Module
PLC
Microprocessor
Output Module
Actuator
Process
Input Module
Sensor

63. PLC consists of the following components:•
Microprocessor – This is the brain of PLC. It reads input signals, executes control program and communicates results (decisions) of control program as action signals to the outputs. •
Memory – It stores control program that is to be executed at a prescribed rate.
Power Supply – This component is used to convert the mains AC voltage to the low DC voltage (e.g. from 240V AC to 5V DC). This unit powers the processor and the circuits in the input and output modules.
Input Module – This component receives information from external devices (sensors). It contains circuitry that provides electrical isolation and signal conditioning functionalities. Input module can be analogue input (AI) or discrete input (DI) module. AI module receives continuously changing signal whose amplitude is proportional to the current value of the measured process variable. DI module receives discrete/digital (ON/OFF) information from discrete sensors, for example push button (ON if button is pressed, OFF if button is not pressed). Note that DI is much more frequently used than AI. •
Output Module – This module communicates control actions to external devices (actuators). It contains circuitry required to interface PLC with actuators (e.g. digital-to- analogue converter and power amplifier). Like input module, output module can be analogue output (AO) or discrete output (DO) module depending on the type of actuator used. •
Communication Module – This component allows PLC to communicate with external devices using sophisticated multiple-bit digital communication protocols (e.g. Ethernet).

64. Programmable Logic Controller (PLC)

65. PLC Programming Ladder Diagram - most common
Structure Text Programming (ST)
Functional Block Programming (FB)
Instruction List (IL)
Sequential Function Chart (SFC)

66. Supervisory Control and Data Acquisition (SCADA)•
SCADA system performs the following tasks
Collection of data from field devices, which can be sensors, actuators and controllers.
Transfer of field devices’ information via communication link to the central site (master station)
Execution of any necessary analysis and supervisory control calculations, all of which are taking place at the master stations.
Display process information on a number of operator screens.
Convey any required supervisory control actions back to the field devices.