| 摘要 |
A first circuit element is provided that is capable of being coupled to an electrical power source to provide a voltage output. A motor (20) for mechanically pumping a fluid in the pump system is responsive to the voltage output. A switching circuit element (18) receives the voltage output and alternately cuts off and conducts current to the motor (20) in response to a control signal (36). A pressure transducer (22) is provided to measure the fluid pressure in a fluid discharge line of the pump system. The pressure transducer (22) develops a sensed voltage representative of the measured fluid pressure. A pressure sensor circuit (32) compares the sensed voltage to a set point voltage representative of a desired fluid pressure (34). The pressure sensor (32) circuit causes the switching circuit element (18) to cut off current to the motor (20) when the sensed voltage exceeds the set point voltage, and causes the switching circuit (18) to conduct current to the motor when the sensed pressure is less than the set point pressure. The present invention also provides a novel capacitive pressure transducer (22) for use in a pump system that is very accurate and inexpensive. The pressure transducer (22) includes a first plate and a second plate spaced a distance from each other. The second plate is deformable and exposed to the fluid pressure in the pump system. The fluid pressure causes the second plate to deform toward the first plate, varying the capacitance of the pressure transducer. The variance is expressed as a voltage change proportional to the magnitude of the fluid pressure measured. |
