The PTU module contains separate sensors for pressure, temperature, and humidity measurement.
The PTU module includes:
- Capacitive silicon BAROCAP sensor for pressure measurement,
- Resistive thin-film Pt1000 sensor for air temperature measurement
- Capacitive thin-film polymer HUMICAP R2 sensor for humidity measurement.
In case of capacitive sensors, the measurement principle of the transmitter is based on an advanced RC oscillator and reference capacitors against which the capacitance of a sensor is continuously measured. The resistive Pt1000 sensors are measured with a voltage divider circuit incorporating a reference resistor and a stable voltage source. Using mathematical sensor response models and the information from sensor calibrations, the microprocessor of the transmitter performs transformations from measured electrical parameters to reported environmental parameters. These calculations include compensation for the temperature dependency of the pressure and humidity sensors.