Function

Transmitter for Pressure and Level

The PTE200 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.

PTE200H has microcomputer-based electronics, which communicate with the outside world with 4 to 20 mA signal as well as HART communication. 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 communi-cation in optional engineering units, percentage or current.

PTE200H 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 communication.

Transmitter for Differential Pressure

The transmitter has a central piezo-resistive sensor connected to the membrane chambers via two capillary tubes.

Each of the two process media pressures act on a separating membrane that have a small spring constant. An overload membrane with adapted spring constant is located between the two separating membranes. The membrane chambers and the sensor are filled with silicon oil. The pressure on both sides of the overload membrane is transferred to the sensor by means of the silicon oil.

At a pressure difference between the two separating membranes within the measuring range of the transmitter, all three membranes will move freely. At overload exceeding the measuring range one of the separating membranes will however lay against the profiled surface while the overload membrane still can move freely. The differential pressure across the sensor can in that way not increase further even if the differential pressure across the separating membranes increases. This protects the sensor against overload and transient pressure surges.

The electronics perform compensation for temperature drift of the sensor by means of compensation values entered at 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 converts the digital value to an analogue signal for the current loop 4 to 20 mA. The digital value can also be read via HART communication in optional engineering quantity, percentage or current.

PTE200H can be configured/calibrated to a certain part by means of keys and switches in the connection space and fully by means of a hand terminal or a PC via HART communication.