VII.5.1.2 Resistance Temperature Detector (RTD)

The RTD incorporates pure metals or certain alloys that increase in resistance as temperature increases and, conversely, decrease in resistance as temperature decreases. RTDs act somewhat like an electrical transducer, converting changes in temperature to voltage signals by the measurement of resistance. The metals that are best suited for use as RTD sensors are pure, of uniform quality, stable within a given range of temperature, and able to give reproducible resistance-temperature readings. RTD elements are normally constructed of platinum, copper, or nickel. These metals are best suited for RTD applications because of their linear resistance-temperature characteristics.

(VII.6)

The above equation represents the Resistance vs. Temperature relationship where R is the resistance and temperature T , with reference Resistance and coefficient of resistance as The coefficient of resistance is the change in resistance per degree change in temperature, usually expressed as a percentage per degree of temperature.

VII.5.2 Pressure Measuring Devices

Most common devices for pressure measurement are differential pressure transducer.