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2 | UNIK 5*00 Series–English
UNIK pressure sensors are optionally available with certification permitting their use in explosive
atmospheres.
2.2 Technical Specifications
Refer to the appropriate UNIK 5*00 data sheet for technical specifications and explanation of the
product model number.
Model numbers appended with a four or eight-digit alphanumeric string denote the use of a
customer-specific specification drawing indicating the use of additions or deviations to the data
sheet specification. Refer to the specification drawing if applicable.
2.3 Design and Principle of Operation
The sensor consists of a pressure connector, pressure measuring module, a partially
encapsulated electronics module, and electrical connection facilities, structurally combined in a
cylindrical metal housing.
The pressure connector allows the sensor to be mounted to a pressurized vessel or pipework.
The pressure measuring module consists of a welded metal body featuring a metal diaphragm
(providing a flexible barrier to the process media), a glass-to-metal seal (for electrical
connections) and a fluid filled cavity containing a silicon diaphragm with diffusion implanted
resistors arranged in the form of a Wheatstone bridge.
The operating principle of the pressure sensor is based on the piezo resistive effect: a change in
resistance when applying pressure. When pressure is applied, the silicon diaphragm flexes,
changing the resistance of the implanted resistors and the output voltage of the bridge circuit.
For sensors designed to measure ‘gauge’ or ‘atmospheric’ pressure, the rear of the silicon
diaphragm is vented to the external atmosphere via a PTFE filtered port in the body of the
enclosure, or via a tube in the supplied electrical cable.
The electronic circuit, available in three main variants (“PMP”, “PDCR” and “PTX”) provides a
range of electrical connection and electrical output signal options.
Depending on the type of electrical connection facility provided, the 'zero' and 'span' settings of
the sensor can be adjusted.
Depending on the type of electrical output and electrical connection of the sensor, it is possible,
by connecting certain electrical contacts together, to receive an output signal simulating an
external pressure equal to 80% of the full scale. This is the ‘Shunt Calibration’ feature of the
sensor.
