Self-calibrated subcarrier telemetry system
First Claim
1. In combination with apparatus having a stationary member, and a heavy rotational member or rotor adapted to rotate at high speed within said stationary member, a telemetry system for detecting strain on a part of said rotational member comprising:
- (a) a transducer-data transmission portion mounted on and rotatable with said rotational member;
(b) a stationary data reception-readout portion having means for generating a radio frequency (RF) signal, said RF signal being supplied to said transducer-data transmission portion and to said data reception-readout portion;
(c) means for inductively coupling signals between said transducer-data transmission portion and said data reception-readout portion;
(d) said transducer-data transmission portion including(d1) a first means for frequency division of said RF signal to provide a lower frequency subcarrier signal;
(d2) a strain gage transducer adapted for excitation by said subcarrier signal and responsive to strain on said rotational member by producing a corresponding amplitude modulated signal at the subcarrier frequency;
(d3) an FM transmitter for receiving said amplitude modulated signal and generating a carrier signal for transmission through said inductive coupling means to said stationary data reception-readout portion, said carrier signal being frequency modulated by said amplitude modulated signal; and
(e) said data reception-readout portion including(e1) a second means for frequency division of said RF signal to provide a reference signal equal in frequency to said subcarrier signal;
(e2) an FM receiver for receiving and demodulating said carrier signal to yield said amplitude modulated signal; and
,(e3) a synchronous detector having a first input for receiving said reference signal and a second input for receiving said amplitude modulated signal from said FM receiver, said synchronous detector producing a demodulated signal representative of strain on said rotational member.
0 Assignments
0 Petitions
Accused Products
Abstract
A self-calibrating subcarrier telemetry system for measuring strain on rotating members of a turbine under operating conditions. A rotor mounted portion of the system includes a strain gage transducer bridge excited by a subcarrier alternating current derived from an induced power source. The transducer bridge produces an output signal, amplitude modulated by the strain signal whereby the modulation shifts the strain signal into a higher frequency portion of the spectrum away from low-frequency noise related to the rotational speed of the turbine. A calibration signal is introduced by automatically unbalancing the bridge transducer periodically at a rate related to the subcarrier frequency. The strain signal is recovered in a stationary data reception portion of the system by a synchronous detector. A reference calibration signal is provided against which receiver gain is adjusted to achieve a null, leaving only the calibrated strain signal and achieving indpendence of variations in system gain. Nulling against the unipolar calibration reference further provides a means to distinguish tensile and compressive strain.
-
Citations
8 Claims
-
1. In combination with apparatus having a stationary member, and a heavy rotational member or rotor adapted to rotate at high speed within said stationary member, a telemetry system for detecting strain on a part of said rotational member comprising:
-
(a) a transducer-data transmission portion mounted on and rotatable with said rotational member; (b) a stationary data reception-readout portion having means for generating a radio frequency (RF) signal, said RF signal being supplied to said transducer-data transmission portion and to said data reception-readout portion; (c) means for inductively coupling signals between said transducer-data transmission portion and said data reception-readout portion; (d) said transducer-data transmission portion including (d1) a first means for frequency division of said RF signal to provide a lower frequency subcarrier signal; (d2) a strain gage transducer adapted for excitation by said subcarrier signal and responsive to strain on said rotational member by producing a corresponding amplitude modulated signal at the subcarrier frequency; (d3) an FM transmitter for receiving said amplitude modulated signal and generating a carrier signal for transmission through said inductive coupling means to said stationary data reception-readout portion, said carrier signal being frequency modulated by said amplitude modulated signal; and (e) said data reception-readout portion including (e1) a second means for frequency division of said RF signal to provide a reference signal equal in frequency to said subcarrier signal; (e2) an FM receiver for receiving and demodulating said carrier signal to yield said amplitude modulated signal; and
,(e3) a synchronous detector having a first input for receiving said reference signal and a second input for receiving said amplitude modulated signal from said FM receiver, said synchronous detector producing a demodulated signal representative of strain on said rotational member. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
-
Specification