초록 ▼

A differential pressure measuring system is disclosed. The system includes two quartz capacitive pressure transducers (14, 16). Each capsule contains a pressure sensitive capacitor (Csa, Csb) and a relatively pressure invariable reference capacitor (Cra, Crb). The pressure sensitive capacitors (Csa,

A differential pressure measuring system is disclosed. The system includes two quartz capacitive pressure transducers (14, 16). Each capsule contains a pressure sensitive capacitor (Csa, Csb) and a relatively pressure invariable reference capacitor (Cra, Crb). The pressure sensitive capacitors (Csa, Csb) are excited by out-of-phase signals, (Vr, -Vr) which further excite the reference capacitors (Cra, Crb), out of phase, respectively. The outputs of all capacitors are combined in a summing junction (22) whose output controls the count of a digital integrator (34). A closed loop is formed by converting the output of the integrator (34) to a negative feedback signal (lf) which is applied to the summing junction (22) through a feedback capacitor (Cf). The integrator (34) incrementally changes the feedback signal (lf) in a direction to balance the loop. At this point the output of the integrator (34) is representative of the measured differential pressure.

대표청구항 ▼

A differential pressure measuring system comprising: means for generating first and second alternating reference signals having a predetermined phase relationship therebetween; a first pressure sensitive impedance, responsive to a first pressure, driven by said first reference signal for generating

A differential pressure measuring system comprising: means for generating first and second alternating reference signals having a predetermined phase relationship therebetween; a first pressure sensitive impedance, responsive to a first pressure, driven by said first reference signal for generating a signal proportional to the change in the first pressure; a second pressure sensitive impedance, responsive to a second pressure, driven by said second reference signal for generating a signal proportional to the change in the second pressure; means, electrically connected to said first and second impedances, for generating an analog error signal which is proportional to the difference between said first and second pressures; means for converting said analog error signal into a digital error signal; means for integrating said digital error signal and generating a digital output number N therefrom; means for converting said digital output number into an alternating feedback signal of the same phase as one of said reference signals; wherein said feedback signal is fed back to said analog error signal generating means through a feedback impedance to null said analog error signal; and said digital output number N being representative of the difference in said first and second pressures when the digital error is nulled.