Displacement converter

• US 4,357,834 A
• Filed: 09/03/1980
• Issued: 11/09/1982
• Est. Priority Date: 09/03/1980
• Status: Expired due to Term

• Current Assignee: Hokushin Electric Works Limited
• Original Assignee: Hokushin Electric Works Limited
• Inventors: Kimura, Atsushi
• Primary Examiner(s): Woodiel, Donald O.
• Application Number:
  US06/183,631
• Time in Patent Office: 797 Days
• Field of Search: 73/706, 73/724, 73/718, 73/708, 331/65, 361/283
• US Class Current: 73/708
• CPC Class Codes: G01L 9/0072 using variations in capacitance
• CPC Class Codes: G01L 9/12 by making use of variations in capacitance , i.e. electric circuits therefor

Abstract

A displacement converter useful for pressure gauges and similar instruments, the converter including a displacement detector provided with a variable capacitor responsive to the displacement to be metered and a fixed capacitor insensitive thereto. Also included is an amplitude-controllable oscillator whose AC output is applied to both capacitors, means being coupled to the capacitors to derive therefrom electrical signals which are a function of their capacitance values. These electrical signals are fed to a control circuit to produce a control signal corresponding to the difference therebetween, the control signal being applied to the oscillator to govern the output amplitude thereof in a manner maintaining the control signal at a constant value.

Claims

1. A displacement converter useful in pressure gauges and the like, the converter comprising:

A. a displacement detector having a variable capacitor responsive to the displacement to be metered and a fixed capacitor insensitive thereto;

B. an amplitude-controllable oscillator whose AC output is applied to both the variable and fixed capacitor;

C. means coupled to the variable and fixed capacitors to derive therefrom first and second electrical signals which are a function of their respective capacitance values;

D. a control circuit responsive to the first and second electrical signals to produce a control signal which depends on the difference therebetween; and

E. means to apply said control signal to the oscillator to govern the output amplitude thereof in a manner maintaining the control signal at a constant level.

2. A converter as set forth in claim 1, wherein said detector includes a sensing diaphragm coupled to a movable electrode which is constituted by an annular plate whose periphery is attached by a resilient element to a metal ring concentric therewith, an insulation block disposed in parallel relation to said ring and said movable electrode, said insulation block having a first annular electrode thereon which faces said movable electrode to define said variable capacitor and a second annular electrode therein concentric with said first annular electrode and facing said ring to define said fixed electrode.

3. A converter as set forth in claim 2, wherein said first annular electrode has a marginal extension which faces said ring.

4. A displacement detector as set forth in claim 1, wherein said means coupled to said capacitors include a diode in series with a resistor connected to said variable capacitor to produce said first signal and a diode in series with a resistor connected to said fixed capacitor to produce said second signal.

5. A displacement converter as set forth in claim 4, further including a smoothing capacitor connected across each resistor.

6. A displacement converter as set forth in claim 5, wherein said control circuit includes an operational amplifier to whose input said first and said electrical signals are applied.

7. A displacement converter as set forth in claim 6, further including an amplifier coupled to the output of said operational amplifier to compare the output thereof with a reference voltage to produce said control signal.