| 摘要 |
<p>The unit serves to convert an electrical control signal (I) received at the input of the unit into a pneumatic signal (P). This is emitted at the output of the unit and its value should be proportional to the value of the control signal (I). The unit comprises a tongue-shaped piezoelectric element (6) which is loaded with a voltage dependent on the control signal, so that the element (6) carries out a lateral bending movement which varies with the voltage. The unit also comprises a pneumatic line (1) with a chamber (1a) which is supplied with compressed air via a throttle (4) and from which the compressed air is conducted through a nozzle (3) located near to one side of the piezoelectric element (6) so that the air pressure in the chamber is regulated by the piezoelectric element (6) as a function of the said voltage; and an outlet line (5) leading from the chamber for transmitting the regulated air pressure to the control system as the said pneumatic signal (P). To make the pneumatic signal (P) to the control system accurately follow the electrical control signal (1), a pressure transducer (7) is connected to the outlet line (5), being designed to produce an electrical signal (T) which corresponds to the regulated air pressure, and which is fed back via a feed-back circuit to the input of the unit. Furthermore, the input has a circuit (9, 11) which receives both the electrical control signal (1) and the fed-back electrical signal (T). The circuit has a device (9) for forming a difference signal by comparing the two signals (I, T) and a device (11) for integrating the difference signal and thereafter producing from the integrated difference signal the voltage with which the piezoelectric element (6) is loaded. </p> |
