Transmitter for Pressure and Level
The PT60 uses a piezo-resistive pressure sensor which is connected to the pressure of the medium via a capillary tube and a diaphragm. Media pressure applied to the diaphragm is transferred via silicon oil to the pressure sensor. The oil completely fills the cavity in the sensor, the capillary tube and the cavity above the diaphragm. This means that the diaphragm movement is very small at pressure changes. The capillary tube protects the pressure sensor from transient pressure surges.

To ensure that the sensor has the correct reference pressure, the rear side is connected to ambient atmospheric pressure, via a tube, designed in order that air passes “cold surfaces” closest to the pressure connection of the transmitter. Any humidity in the air will condense on these surfaces. The condensate flows out and the remaining air in the tube stays dry. Additionally, the reference pressure connection is designed to prevent flushing water from entering.

PT60 has microcomputer-based electronics, which communicate with the outside world with 4 to 20 mA signal as well as HART communication (PT60H). The electronics measure and converts the output signal from the pressure dependent sensor bridge to digital values. Furthermore, the total resistance of the sensor bridge is measured and these values are converted to digital temperature values.

The electronics perform compensation for temperature drift of the sensor by means of compensation values entered at the factory calibration and at the same time the temperature measurement is also calibrated. Compensation for the non-linearity in the sensor is done in the same manner.

Different kinds of transfer functions, such as linear, square root, curves..., can be selected. The electronics perform the calculation for the selected transfer function and then the digital value is converted to analogue for the 4 to 20 mA current loop. The digital value can also be read via HART (PT60H) communication in optional engineering units, percentage or current.

PT60 can be configured/calibrated to a certain extent by means of keys and switches in the connection space and fully by means of a hand terminal or a PC via HART (PT60H) communication.