Process Variables

• Temperature: measure of the average kinetic energy possessed by the molecules of the substance
• Resistance Thermometer: electrical resistance of a conductor
• Thermocouple: voltage at the junction of two dissimilar metals
• Pyrometer: spectrum of emitted radiation
• Thermometer: volume of a fixed mass of fluid
• Temperature scales: "temperature scales are defined using the freezing point and boiling point of water at a pressure of 1 atm
• Pressure: ratio of a force to the area on which the force acts
• Atmospheric Pressure: pressure on the earth’s surface which is a result of the air’s weight above the surface
• Absolute Pressure: pressure that considers absolute zero pressure or perfect vacuum as its reference point
• Gauge Pressure: difference between the measured pressure and the local atmospheric pressure
• Differential Pressure: difference between two applied pressures
• Hydrostatic Pressure: pressure that is exerted by a fluid at equilibrium at a given point within the fluid, due to the force of gravity
• Pressure Head: height of a hypothetical column of this fluid that would exert the given pressure at its base if the pressure at the top were zero
• Manometer: U-shaped tube partially filled with a fluid of known density (the manometer fluid). When the ends of the tube are exposed to different pressures, the liquid level drops in the high-pressure arm and rises in the lowpressure arm
• Resistance thermometer

  
• Thermocouple: a thermoelectric device for measuring temperature, consisting of two wires of different metals connected at two points, a voltage being developed between the two junctions in proportion to the temperature difference.

  
• Pyrometer

  
• Thermometer

  
• Bourdon-Tube gauge

  
• Diaphragm gauge

  
• Manometer

  
• Piezoresistive Transducers

  
• Piezoelectric Transducers