WELCOME

SILICON-CARBIDE BASED TEMPERATURE SENSOR

USING OPTICAL PYROMETRY AND LASER

INTERFEROMETRY

Temperature is one of the most fundamental parameter.

Temperature measurement is necessary in most industrial plants for controlling processes.

Especially in gas turbines we need very high temperature measurement systems.

INTRODUCTION

USES FIRING TEMPERATURE OF 1430°C

COMBUSTION SECTION TEMPERATURE IS 1500°c

TEMPERATURE RANGE

THERMISTOR (-100 to 300 °C) RTD (-250 to 850 °C) THERMOCOUPLE (-200 °C to 2000 °C )

Usually thermocouples are using for industrial applications.

But its lifetime is limited .

DISADVANTAGES OF THERMOCOUPLE

Direct contact to harsh environment

Develop cracks in insulation

Picks moisture

Become conductive and explodes

RELIABLE SOLUTION

Silicon carbide based system will be a reliable solution

Melting Temperature ~ 2500 °C Natural Interferometer Chip High Refractive Index ~2.55 Mechanically robust

OPTICAL PYROMETERYNon-contacting method for measuring thermal radiation

LASER INTERFEROMETRYwhich makes use of principle of super position

PYROMETER

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

A pyrometer has an optical system and detector

optical system focuses the thermal radiation onto the detector

The output signal of the detector is related to the thermal radiation

INTERFEROMETRY Makes use of the principle of superposition

Combination of different waves will have some meaningful property

Resulting pattern is determined by the phase difference between the two waves

In phase will undergo constructive interference

Out of phase will undergo destructive interference.

TUNABLE LASER

Laser whose wavelength of operation can be altered in a controlled manner.

• santec TSL-210 tunning range(1520-1600nm)

Silicon carbide (SiC), also known as carborundum.

Compound of silicon and carbon with chemical formula SiC

It is used as a black bodyradiater

A beam splitter is an optical device that splits a beam of light in two.

half of the light incident through face of the cube is reflected and the other half is transmitted due to total internal reflection

Convert light signals to a voltage or current

The absorption of photons creates electron hole pairs which creates proportional voltage.

Optical filters selectively transmit light having certain properties

They are of different types like band pass, band reject, high pass, low pass etc..

• Optical filters: F1= 10LF30-1550 F2= 10LF30-1300

λ= emitted radiation wavelengthT= temperatureH= planks constant(6.62606957×10−34)

C= speed of lightK= boltzmann’s constant(1.380 64×10−23)

ACCRODING TO PLANK’S LAW

As= SENSOR SPECIFIC CONSTANT€= SPECIFIC EMISSIVITY OF SiCC= hc/k

R=ratio of power output;

α , β =constants determined by sensor calibration;

T=temperature;

FINDING α AND β

R VS T (calibration curve)

FIG:2

Using the R vs. T calibration curve, we can find the course temperature value.

By measuring R and finding corresponding T from the graph.

COURSE TEMPERATURE MEASUREMENT

P VS T CURVE

P VS λ CURVE

Pmin AND Pmax LOCALIZED MINMUM AND MAXIMUM POWER VALUES

It measured temperature with:

• 0.1°c resolution

• .44% accurate than thermocouple

• But For a different heating environment, the sensor would have to be recalibrated

Wikipedia http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?

arnumber=5361373 N. A. Riza, M. Sheikh, and F. Perez; IEEE Sensors

J., vol. 6, pp. 672–685, 2006. L. Cheng, A. J. Steckl, and J. Scofield; Devices, vol.

50, pp. 2159–2164, 2003. N. A. Riza and M. Sheikh, Opt. Lett., vol. 33, pp.

1129–1131, 2008.

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