| 摘要 |
Apparatus for producing output signal changes corresponding to fluid pressure changes includes: (a) a transducer responsive to applied input pressure changes to produce capacitance changes at a variable capacitor, (b) a first circuit to produce a cyclic wave, and connected with the variable capacitor, (c) a second circuit including a switch to connect the capacitor to ground when the cyclic wave is at a first level, thereby to charge the variable capacitor, and to connect the variable capacitor to a second capacitor when the cyclic wave is at a second level, whereby the charge becomes distributed on the variable and second capacitors, and whereby a sawtooth signal is produced at a junction associated with the capacitors, (d) an operational amplifier electrically coupled with that junction for integrating the sawtooth signal to produce a first output voltage, (e) the first circuit including a voltage controlled oscillator having an input side coupled with the output side of the operational amplifier thereby to produce the output signal in the form of a frequency which varies as a function of the first output voltage and which corresponds to the cyclic wave, (f) stray capacitance being introduced by electrical connections associated with the transducer and the second circuit, and including a third circuit operatively connected with second circuit for masking the effect of stray capacitance, (g) the second circuit including resistance connected between a source of DC voltage and the junction.
|
