Title:
【発明の名称】状態検出装置
Document Type and Number:
Japanese Patent JP2532202
Kind Code:
B2
Abstract:
In a circuit for coupling a transducer having a reactive sensing element (ZS) to equipment providing either AC or DC drive voltage which is equipped with (strain gauge) amplifiers, the sensing impedance (ZS) varies the gain of the feedback loop of an oscillator, an AGC circuit (6) is coupled to the loop so as to derive a control signal related to the amplitude of oscillations therein and a gain control means (4) is included in the loop that responds to the control signal in such manner as to restore the loop gain to unity after it has been changed therefrom by changes in the value of the sensing impedance (ZS). If the gain control means (4) is a voltage divider having a variable resistor as the operative element, a matched variable resistor is used as the unbalancing element of a resistive bridge (8), and the values of the circuit are chosen such that the output signal from the bridge which may be applied to strain gauge amplifiers is linearly or desirably nonlinearly related to changes in the value of the reactive sensing impedance (ZS). Operating potentials for the oscillator are derived by a rectifier from the drive voltage. If the control signal is to be used as a linear output signal, the variable resistor of the voltage divider is made to have a suitably nonlinear relation with respect to the value of the control signal. The variable resistor can be a nonlinear digitally controlled resistor in which event the control signal can be digitized without using an A/D converter.
Inventors:
EDOIN BII MERITSUKU
Application Number:
JP6984485A
Publication Date:
September 11, 1996
Filing Date:
April 02, 1985
Export Citation:
Assignee:
HEWLETT PACKARD CO
International Classes:
G08C19/04; G01D3/02; G01D5/24; G01L9/12; G01R17/06; G01R17/10; G01R27/26; H02M7/12; H02M7/21; (IPC1-7): G08C19/04; G01D3/02
Domestic Patent References:
| JP5821502A | ||||
| JP5821503A |
Attorney, Agent or Firm:
Hideo Ueno (1 outside)