Study and dynamic modeling of a pressure transducer that is based on the principle of force balance

The work reported here shows the development of an analytical model for one type of pressure transducer that is used in nuclear power plants. It is a Foxboro El3DM force balance transducer with applications for flow, level and low pressure measurements.

The model is based in studying the propagation of mechanical vibrations through the mechanical linkages of the transducer. The electronic circuit of the transducer is responsible for the feedback force that balances the system, and it was considered in the model.

The frequency response as predicted by the model was compared with three sets of experimental data. The results showed good agreement in the region of analysis.

The non-linear behavior of the transducer is explained, and the conditions for linear response are discussed.

Two 'in-situ' tests were developed for the transducer. One can be performed remotely, during normal operation of the plant. The other requires access to the transducer. The tests allow one to obtain the step response of the transducer.

Neither of the tests require access to the pressure line.