Digital Pressure Sensor
Digital Pressure Sensor Type
Applications of digital pressure sensor
Atmospheric pressure or altitude measurement.
Engine control, pneumatic and hydrolic machines
Process monitoring and control
HVAC in commercial building
Comparison between of Thermocouple and RTD
Cost: Comparing to RTD, Thermocouple is lesser expensive.
Temperature Range: Extends to about 1150°C or higher. However, the thermocouple’s cryogenic range is somewhat less than that of the RTD.
Mounting cost: Lower than RTD
Ruggedness: For process environmental condition, high temperature, vibration, thermocouple are regarded highly.
Stability: Less than for the RTD. Estimated at 0.6◦C (1◦F) per year.
Calibration: Nonlinear over normal spans. Signal requires linearizing. Calibration can be changed by contamination.
Accuracy: Generally expected, after installation, ±4◦C (±7.2◦F), but there are exceptions. Thermocouple requires reference junction or special wires. The inaccuracy is due to two separate temperature measurements - the measuring junction and the cold or reference junction.
Accuracy: Accepted after installation ±0.5◦C. The platinum RTD, for example, is used to define the IPTS at the oxygen point (−182.97◦C) and the antimony point (+630.74◦C).
Repeatability: Within a few hundredths of a degree; can often be achieved with platinum RTDs. Less than 0.1% drift in 5 years.
Relatively narrow spans: Some versions may have spans as narrow as 5.6◦C (10◦F).
Substantial output voltage (1 to 6 volts): This is an advantage in that the output can be controlled by adjusting the current and the bridge design in the RTD signal conversion module. Because of a higher output voltage to the RTD and controlling of temperature signals is simpler. This permits more accurate measurements without requiring complex calculations for large spans
Compensation: Not required.
Size: Generally smaller than thermocouples
Cost: Higher than the thermocouple. RTDs do not require compensation, special lead-wires, and special signal conditioning for long runs.
Less rugged: For adverse process environments, including high temperature and vibration.
Lower temperature range: Limited to about 870◦C (1600◦F).
Self-heating errors: This may be a problem unless corrected in the transistor’s electronics.