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Temperature Measurement Scales

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Temperature Measurement Scales

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  1. ABOUTINSTRUMENTATIONInstrumentation is used in almost every industrial process andsystem, where consistent and reliable operations are required.Instrumentation provides the means of monitoring, recording and controlling a process to maintain it at a desired state. A typical industrial plant such as an electric generating station (figure-Electrical Generating System) yield many process variables that have to be measured

  2. Temperature Measurement Scales (°F) = 9/5*(°C) +32 (°C) = 5/9*[(°F) –32] (°F) = (°R) – 459.67 (°C) = (K) – 273.15 Methods of Temperature Measurement Thermocouples Thermistors Electrical resistance change (RTD) Pyrometers

  3. When 2 dissimilar metals are joined together to form a junction, an emf is produced which is proportional to the temperature being sensed. The magnitude of emf depends on the junction temperature. THERMOCOUPLE

  4. Simplified Thermocouple Temperature Transmitter Circuit Circuit emf = Measurement emf - Reference emf

  5. THERMISTOR • The resistance of thermistors decrease with increases in temperature. • The operating range can be -200°C to + 1000°C • The thermistors can be in the shape of a rod, bead or disc.

  6. Resistance Temperature Detector- RTD RTD (Resistance Temperature Detector) is a temperature sensitive resistor. It is a positive temperature coefficient device, which means that the resistance increases with temperature. The resistive property of the metal is called its resistivity. PLATINUM WIRE RTD • linear temperature sensors • Resistance vs temperature characteristics are stable and reproducible

  7. Platinum Scale ( 0 to 100 °C )

  8. Wheatstone Bridge Temperature Detector for an RTD

  9. RELATION GRAPH BETWEEN THERMISTOR,RTD,THERMOCOUPLE

  10. PYROMETER Pyrometry is a technique for measuring temperature without physical contact An apparatus for measuring high temperatures that uses the radiation emitted by a hot body as a basis for measurement. • Radiation pyrometers • Optical Pyrometers OPTICAL PYROMETER • basic principle of using the human eye to match the brightness of the hot object to the brightness of a calibrated lamp filament inside the instrument

  11. Radiation pyrometers

  12. Level Measurement Introduction There are multiple technologies available in the market to measure level. Each and every technology works, when applied appropriately

  13. Different types of Level Measurement Techniques Differential Pressure type Capacitance Displacers / Floats Bubbler

  14. Differential pressure type - A DP is used to transmit the head pressure that the diaphragm senses due to the height of the material in the vessel multiplied by a density variable. • Advantage:- the most frequently used device for the measurement of levelis a differential pressure transmitter. Using DP for level is really an inferential measurement. DIFFERENTIAL PRESSURE

  15. Closed Tank Level Measurement Open Tank Level Measurement

  16. Capacitance - A capacitance transmitter which converts capacitance signals input to a standard 4-20 mA output. Together with a capacitance probe, the tx is used to measure a continuous level or interface of liquids • Advantage:-Accurate level measurement independent of sticky or crystalline cotaing or varying moisture content of granulars. • Capacitance Type Level measurement

  17. Displacers/Floats-when a body is immersed in a fluid it loses weight equal to that of the fluid displaced. By detection of the apparent weight of the immersed displacer, a level measurement can be inferred. When the cross sectional area of the displacer and the density of the liquid is constant, then a unit change in level will result in a reproducible unit change in displacer weight. DISPLACER/FLOAT

  18. BUBBLER LEVEL MEASUREMENT SYSTEM • If the process liquid contains suspended solids, or is chemically corrosive orradioactive, it is desirable to prevent that fluid from coming into direct contactwith the level transmitter. • In these cases, a bubbler level measurement system can be used.

  19. Bubbler Level Measurement System

  20. PLC(programming logic control) • Programmable logic controllers are the most widely used electronic devices in the control of production and assembly process in most automated factories due to its simplicity and versatility. • Initially designed to replace relay logic boards • Sequence device actuation • Coordinate activities • Accepts input from a series of switches • Sends output to devices or relays

  21. INTRODUCTION PLC

  22. PLC ARCHITECTURE

  23. Can be installed in a very basic configuration, then expanded and enhanced as needed in the future • Multiple computers facilitate parallel multitasking • Redundancy due to multiple computers • Control cabling is reduced compared to central controller configuration

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