transmitters and signal conditioning element

unit 2 and 3

1. Unit 2 TRANSMITTERS AND SIGNAL CONDITIONING

2. Standards used for signal transmission from sensor to controller in industrial processes: Pneumatic pressure 3 - 15 psig,  20 - 100 kPa Voltage 0 - 10 V (or 0 - 5 V) Electric current (direct current) 4 - 20 mA

3. 2-wire , 3 wire and 4 wire transmitters

4. Signal Conditioning (RTD)

5. Signal Conditioning (Thermistor) Because these devices are resistances, care must be taken to ensure that power dissipation in the thermistor does not exceed the limits specified Dissipation constants are quoted for thermistors as the power in milliwatts required to raise a thermistor’s temperature 1°C Typical values vary from 1 mW /°C in free air to 10 mW /°C

6. Signal Conditioning (Thermocouple) The key element in the use of thermocouples is that the output voltage is very small, typically less than 50 mV. This means that considerable amplification will be necessary for practical application. In addition, the small signal levels make the devices susceptible to electrical noise . In most cases, the thermocouple is used with a high-gain differential amplifier.

7. Smart / Intelligent Transmitters Smart / Intelligent Actuators 8 Smart/Intelligent Transmitters & Actuators © 2014: Dr. H. K. Verma CONTENTS

8. Smart Transmitter: It is a compact unit comprising a sensor (or sensors), analog signal processing unit, transmitter circuit and a communication port. Intelligent Transmitter: It is a compact unit comprising a sensor (or sensors), analog signal processing unit, data processor, communication interface and a communication port. Variants: A – Smart transmitter with analog output B – Intelligent transmitter with digital wired input-output C – Intelligent transmitter with digital wireless input-output D – Intelligent HART transmitter E – Intelligent HART transmitter with advanced features 4.1 Smart / Intelligent Transmitters 9 Smart/Intelligent Transmitters & Actuators © 2014: Dr. H. K. Verma

9. Smart Transmitter with Analog Output Analog Output Options: Voltage or current Most common output: 4-20 mA Sensor Analog signal processing Unit (ASPU) Transmitte r circuit Analog output port Analog output (represents value of the measurand) Measurand 10 Smart/Intelligent Transmitters & Actuators © 2014: Dr. H. K. Verma

10. Intelligent Transmitter with Wired Digital Communication Digital communication (comm.) options: □ Modbus over RS485 Modbus over TCP/IP Ethernet Foundation Fieldbus CANBus, ProfiBus, etc. Sensor Data processing Unit (DPU) Comm. interface Digital comm. port Digital input/output (Digital output represents value of the measurand, Digital input is for configuring the device) Measurand ASPU ADC 11 Smart/Intelligent Transmitters & Actuators © 2014: Dr. H. K. Verma

11. Intelligent Transmitter with Wireless Digital Communication Digital communication (comm.) options: Zigbee (most common) Wi-Fi Bluetooth Sensor Data processing Unit (DPU) Comm. interface Measurand ASPU ADC Antenna RF signal 12 Smart/Intelligent Transmitters & Actuators © 2014: Dr. H. K. Verma

12. Intelligent HART Transmitter Digital communication (comm.) options: □ Zigbee (most common) Wi-Fi Bluetooth Sensor HART Comm. interface HART comm. port Digital input/output (Digital output represents value of the measurand, Digital input is for configuring Measurand ASPU ADC DPU Analog output (Represents value of the measurand) the device) 13 Smart/Intelligent Transmitters & Actuators © 2014: Dr. H. K. Verma

13. Intelligent HART Transmitter Digital communication (comm.) options: □ Zigbee (most common) Wi-Fi Bluetooth Sensor Data processing Unit (DPU) Comm. interface Digital comm. port Digital input/output (Digital output represents value of the measurand, Digital input is for configuring the device) Measurand ASPU ADC 14 Smart/Intelligent Transmitters & Actuators © 2014: Dr. H. K. Verma

14. Functions of Microprocessor in Intelligent Transmitters 15 Smart/Intelligent Transmitters & Actuators © 2014: Dr. H. K. Verma Data Processing Functions Conversion of electrical units to engg. units Noise reduction Linearization of response Auto-calibration Communication Functions Data formatting Error control Timing control Networking

15. Intelligent HART Transmitter with Advanced Features Main sensors Compensating sensor ASPU ADC MPU Comm. interface Comm. port Analog output Digital Input/ output Voltage/curren t regulator Regulated supply Unregulated supply D.C. supply 16 Smart/Intelligent Transmitters & Actuators © 2014: Dr. H. K. Verma

16. Unit 3 CONTROLLERS AND ACTUATORS PID Control

17. Cascade Control

18. Microprocessor Based Controllers

19. Microprocessors are essential to many of the products we use every day such as TVs, cars, radios, home appliances and of course, computers. Microprocessor based controllers are also called as microcontrollers. Microcontroller is a digital integrated circuit which serves as a heart of many modern control applications. Microprocessors and microcontrollers are similar but the architecture of both differs in the applications domains. Microprocessors are employed for high speed applications such as desktop and laptop computers where as the microcontrollers are employed in automation and control applications such as microwave ovens, automatic washing machines, dish washers, engine management systems, DVD players etc. Microcontrollers are embedded inside some other device (often a consumer product) so that they can control the features or actions of the product. Therefore, it is also called as embedded controller.

20. A microcontroller generally has the main CPU core, ROM/ EPROM / RAM and some accessory functions (like timers, pulse width modulator, A/D convertor and I/O controllers) all integrated into one chip. Microcontroller is a computer on a chip that is programmed to perform almost any control, sequencing, monitoring and display function. Another more adaptable form of microcontroller is the programmable logic controller (PLC). image shows the basic structure of a PLC. The PLC is a microprocessor based controller consists of the CPU , memory and I/O devices . These components are integral to the PLC controller. Additionally the PLC has a connection for the programming unit, and printer. The CPU used in PLC system is a standard CPU present in many other microprocessor controlled systems . The choice of the CPU depends on the process to be controlled. Memory in a PLC system is divided into the program memory which is usually stored in EPROM/ROM, and the operating memory.

21. The RAM memory is necessary for the operation of the program and the temporary storage of input and output data . Input/output units are the interfaces between the internal PLC systems and the external processes to be monitored and controlled. Programming unit in the PLC systems is a essential component and are used only in the development/testing stage of PLC program they are not permanently attached to the PLC . Programming unit can be a dedicated a device or a personal computer.

22. programmable automation controller (PAC) Programmable automation controller (PAC) is a term that is loosely used to describe any type of automation  controller  that incorporates higher-level instructions. The systems are used in industrial control systems ( ICS ) for machinery in a wide range of industries, including those involved in  critical infrastructure . A PAC makes it possible to provide more complex instructions to automated equipment, enabling much the same capabilities as PC-based controls in an all-in-one package like a programmable logic controller ( PLC ).

23. PLCs were created in the 1960s as an improvement over relay-based systems. Although more advanced than relay, PLCs still functioned by simple ladder logic that resembled the appearance of wiring diagrams of relay systems. In the beginning, PLCs had limited  memory , required proprietary terminals and lacked remote  I/O  (input/output) capabilities. Additional abilities required adding hardware cards. PC-based programming of PLC was introduced in the 1980s and offered greater abilities, more memory and sequential control. Early PACs came on the scene at the beginning of the 21 st century. PACs offered a combination of the abilities and technologies of distributed control systems ( DCS ) and remote terminal units ( RTU ) as well as some of the abilities offered by PC control. PACs offered more connectivity options and broader control while maintaining smaller packaging and durability for environmental stresses and shock. With these new improvements, PACs were widely adopted.

24. ACTUATORS If a valve is used to control fluid flow, some mechanism must physically open or close the valve. If a heater is to warm a system, some device must turn the heater on or off or vary its excitation. These are examples of the requirements for an actuator in the process-control loop. Notice the distinction of this device from both the input control signal and the control element itself Actuators take on many diverse forms to suit the particular requirements of process-control loops. We will consider several types of electrical and pneumatic actuators. Electrical Actuators The following paragraphs give a short description of several common types of electrical ac tuators . The intention is to present only the essential features of the devices and not an in- depth study of operational principles and characteristics . In any specific application, one would be expected to consult detailed product specifications and books associated with each type of actuator.

25. Electrical Actuators Solenoid

26. Relays One of the most common electro-mechanical switches in a vehicle, the main job of a relay is to allow a low power signal (typically 40-100 amps) to control a higher-powered circuit. It can also allow multiple circuits to be controlled by one signal—for example in a police car where one switch can activate a siren and multiple warning lights at the same time.   Relays come in a host of designs, from electromagnetic relays—which use magnets to physically open and close a switch to regulate signals, current, or voltage—to solid-state, which use semiconductors to control the flow of power. Because solid state relays have no moving parts, they are generally more reliable and have a longer service life. Unlike electro-magnetic relays, solid state relays are not subject to electrical arcs that can cause internal wear or failure. The six common footprint sizes of relays are: Mini ISO relays , a general-purpose relay that comes in an industry standard footprint and fits the needs of many vehicle electrical applications such as lighting, starting, horn, heating, and cooling. Micro relays , which have a micro size plug-in design for use in the automotive industry and adhere to a standard pattern for their electrical terminals. Micro relays are used in a wide range of vehicles to perform switching operations and allow rated switching currents of up to 35 amps. Maxi relays —sometimes also referred to as a power mini relays—are usually rated up to 80 amps and have a heavy-duty contact design for long-term use. They are ideal for applications such as blower fans, car alarms, cooling fans, energy management, engine control, and fuel pumps. ISO 280 Mini, Micro and Ultra relays , a smaller and more compact version of the standard

27. Solenoids Solenoids are a type of relay engineered to remotely switch a heavier current (typically ranging from 85-200 amps). In contrast to the smaller electromechanical cube relays, a coil is used to generate a magnetic field when electricity is passed through it, which effectively opens or closes the circuit. The terms “solenoid” and “relay” can often be used interchangeably; however, in the automotive market, the term solenoid

28. Contactors The contactor is the relay to use when a circuit must support an even heavier current load (typically 100-600 amps). With voltage ratings from 12V DC up to 1200V DC, contactors are a cost-effective, safe, lightweight solution for DC high-voltage power systems.  Common applications include industrial electric motors used in heavy trucks and equipment, buses, emergency vehicles, electric/hybrid vehicles, boats, light rail, mining, and other systems that simply require too much power for a standard relay or solenoid. Contactors typically have an integrated coil economizer to reduce the power required to hold the contacts closed, which helps increase system flexibility and reliability. They are often available with optional auxiliary contacts.

29. DC motor

30. BLDC motor

31. Operating principle The operating principle of BLDC motor is same as that of the DC motor. Conductors facing a particular magnet pole (say N pole) carry current in one direction while those facing the other pole carry current in opposite direction. By virtue of this, the fields created by magnet and armature conductors are always orthogonal to each other as shown in the Fig. . Note the naming convention “direct axis” and “quadrature axis”.  

32. Advantage Main advantages of BLDC machines are: High power density (due to rare earth ND-Fe-B Magnets) Greater efficiency Lower maintenance cost as compared to conventional DC machines

33. Stepper Motor

34. Pneumatic Actuators

35. Hydraulic servos