| 摘要 |
Downhole well bore pressure sensor capacitances for detecting pressure in a borehole and for developing electrical signals as a function of pressure. FET devices are connected between sensor capacitances and an oscillator where the oscillator is actuated by a sensor capacitance input to switch between pre-set voltage levels. Each sensor capacitance serves to sense a different parameter and the use of FET devices as switches alternately couples the capacitances to the oscillator which produces frequency signals where the frequency of each signal is the representation of the parameter from each capacitance. The FET devices are interconnected so that the stray capacitances and leakage currents inherent in such devices are eliminated by a unity gain amplifier which dynamically balances the potential due to capacitance and current leakage across the various elements of the FET devices.
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