Physical measurement dimensions, such as temperature or pressure and tensile forces, can affect glass fibres and locally change the characteristics of light transmission in the fibre. As a result of the damping of the light in the quartz glass fibres through scattering, the location of an external physical effect can be determined so that the optical fibre can be employed as a linear sensor. Light scattering, also known as Raman scattering, occurs in the optical fibre. Unlike incident light, this scattered light undergoes a spectral shift by an amount equivalent to the resonance frequency of the lattice oscillation. The light. | 373 100° 672 212° 273 0° 492 32° 0 -273° 0 -460° °C = 5/9 (°F - 32 ) °F = 9/5 (°C) + 32 K = 273 +°C R = 460 + °F Kelvin & Rankine are absolute scales BOILING POINT OF WATER ICE POINT ABSOLUTE ZERO kELVIN CELSIUS RANKINE FAHRENHEIT Temperature terminology Temperature Measurement Scales Temperature Measurement Technology METALS change in VOLUME in response to change in TEMPERATURE & DISSIMILAR METAL STRIPS having different COEFFICIENT of VOLUME CHANGE. Example: Bimetallic Thermometer Thermocouple (discussed later) Bimetallic Thermometer The degree of deflection of 2 dissimilar metals is proportional to the change in temperature. One end of the spiral (wounded from a long strip of material) is immersed in the process fluid and the other end attached to a pointer. Rugged enough to actuate recorder pen. More resistance to breakage than glass thermometer. Accuracy NOT as good as glass thermometer. Example: Vapour Pressure Thermometer A bulb connected to a small bore capillary which is connected to an indicating device. Indicating device consist of a spiral bourdon gauge attached to a pointer. The bulb is filled with a volatile liquid and the entire mechanism is gas tight and filled with gas or liquid under pressure. Basically the system converts pressure at constant volume to a mechanical movement. Temperature Measurement Technology Expansion & Contraction of FILLED THERMAL FLUIDS This unit is self-contained - therefore no power is needed, hence is naturally explosion proof. The volatile liquid (mercury) expands or contracts with respect to temperature change in the process - apply force on entrapped vapour- thereby causing the bourdon tube to deflect. The deflection is than mechanically converted to a pointer which will interpret temperature on a scale. Example: Quartz Crystal Thermometers Quartz crystal hermetically sealed in a stainless steel cylinder, similar to a thermocouple or RTD sheath but , larger. Quartz crystal converts temperature into a . | 373 100° 672 212° 273 0° 492 32° 0 -273° 0 -460° °C = 5/9 (°F - 32 ) °F = 9/5 (°C) + 32 K = 273 +°C R = 460 + °F Kelvin & Rankine are absolute scales BOILING POINT OF WATER ICE POINT ABSOLUTE ZERO kELVIN CELSIUS RANKINE FAHRENHEIT Temperature terminology Temperature Measurement Scales Temperature Measurement Technology METALS change in VOLUME in response to change in TEMPERATURE & DISSIMILAR METAL STRIPS having different COEFFICIENT of VOLUME CHANGE. Example: Bimetallic Thermometer Thermocouple (discussed later) Bimetallic Thermometer The degree of deflection of 2 dissimilar metals is proportional to the change in temperature. One end of the spiral (wounded from a long strip of material) is immersed in the process fluid and the other end attached to a pointer. Rugged enough to actuate recorder pen. More resistance to breakage than glass thermometer. Accuracy NOT as good as glass thermometer. Example: Vapour Pressure Thermometer A bulb connected to a small bore capillary which
