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A POWER POINT PRESENTATION ON

Presented To : Respected AJAY DADHICH Sir

Presented By : MAHENDRA SINGH R.NO- 09EI22

TOSHNIWAL INDUSTRIES Pvt. Ltd.

company was set-up at Ajmer (Raj.) since 1963, is manufacturing Industrial Measurement and Control Instruments10/30/2012 MAHENDRA SINGH 2

TEMPERATURE MEASURING INSTRUMENTS Thermocouple(TCs) Resistance Temperature Detector (RTD) Thermistors10/30/2012 MAHENDRA SINGH 3

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PRINCIPLE OF T/CSeebeck effectWhen 2 dissimilar metallic

wires are joined together toform a closed circuit an emf is produced when any one of these junctions are heated.10/30/2012 MAHENDRA SINGH 5

TYPICAL INDUSTRIAL THERMOCOUPLE ASSEMBLY

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T/C WITH TEMP RANGESType J K T E N R S10/30/2012

Element Fe/constantan NiCr/NiAl (chromel/alumel) Cu/Constantan Chromel/constantan Nicrosil/Nisil Pt(13%Rh)/Pt Pt(10%Rh)/PtMAHENDRA SINGH

Temperature Range 196 to 760 -190 to 1371 -190 to 399 -196 to 999 0-1280 -18 to 1704 -18 to 17607

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Advantages: Self Powered (does not require a current or voltage source)

Rugged Inexpensive

Simple10/30/2012 MAHENDRA SINGH 9

Disadvantages: Extremely Low Voltage output (mV) Not very stable Needs a reference point

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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.The industry standard is the platinum wire RTD (Pt100) whose base resistance is exactly 100.00 ohms at 0.0 C.

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RTD, the basics Traditionally made up of platinum, nickel, iron or copper wound around an insulator. Temperature range:

From about -200C to 650C.10/30/2012 MAHENDRA SINGH

Thin Film RTD13

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GENERAL SPECIFICATIONS

Resistance element : Pt.100,100 ohms at 0 degree C.

No. of elements : Single or Duplex. Insulating resistance : 10 Mohms at 500V DC

between terminal and outer sheet. Temperature range : -50 degree C to +500 degree C.10/30/2012 MAHENDRA SINGH 15

RTD TYPES3 TYPES RTD

2-WIRE 3-WIRE 4-WIRE

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RTD Wiring Arrangements

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Advantages: RTD

Stable Very accurate Change in resistance is linear

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Disadvantages: Expensive Current source required Small change in resistance Self heating Less rugged than thermocouples.

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Thermistors Thermistor, a word formed by combining thermal with resistor, is a temperature-sensitive resistor fabricated from semiconducting materials.

The resistance of thermistors decreases proportionally with increases in temperature.

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Thermistors, the basics The thermistors can be in the shape of a rod, bead or disc. Manufactured from oxides of nickel, manganese, iron, cobalt, magnesium, titanium and other metals. Temperature Range about -50C to 315C Generally made up of semiconductor materials

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Advantages:

Very sensitive (has the largest output change from input temperature) Quick response More accurate than RTD and Thermocouples

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Disadvantages:

Output is a non-linear function Limited temperature range from -50C to 315C. Require a current source Self heating Fragile(easily damaged)10/30/2012 MAHENDRA SINGH 23

Graphical comparision of Thermocouple, RTD, Thermistor

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A pyrometer is a non-contacting device that intercepts and measures thermal radiation

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WORKING OF

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FEATURES Wide temperature range 700 2000 C or 700 3500 C Fast response and sensitive measuring system Light weight & portable Two measuring ranges in each instrument Operates on two 1.5V dry cells

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