FOP Piezometer

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Rugged , stainless steel construction and safe, the FOP fiber optic piezometers are suitable for use in long term reliability under all conditions of temperature, EMI and vibration.

Our unique design is based on non-contact deflection measurement of a stainless steel diaphragm, as opposed to more conventional measurement techniques.

The pressure transducer is based on Fabry-Perot interferometry. Pressure creates a variation in the length of a Fabry-Perot cavity consisting of the inner surface of the stainless steel diaphragm on one side and of an optical fiber on the other.

Since fiber optic readout units and dataloggers can consistently and accurately measure the cavity length under all conditions of temperature, EMI, humidity, and vibration, the system delivers reliable pressure measurements in the most adverse conditions. The mechanical robustness is assured by the all-welded stainless steel construction, with no epoxy, sealing rubber, or other sort of polymeric material.

Four models of FOP piezometers are available:

The FOP is designed to be embedded in earth fills at concrete/earth interfaces or inserted into boreholes and small-diameter pipes. The end of the FOP is fitted with a high or low air entry filter, which protects the sensing element from solid particles, allowing this model to sense only the fluid pressure to be measured. The filter is easily removable for saturation.

The FOP-F is a thick-wall version of the FOP for use in direct burial applications.

The FOP-C is provided with a pipe thread adapter, enabling the piezometer to be used as a pressure transducer.

The FOP-P is designed to be driven into unconsolidated fine-grain materials such as sand, silt, or clay. The external housing is a thick-wall cylinder fitted with a conical shoe at one end and an EW drill rod or standpipe thread adapter at the cable entry end.