Self-calibrated subcarrier telemetry system
US4225851A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 22, 1979 |
| Grant date | Sep 30, 1980 |
| Priority date | — |
| Expiry date | Mar 22, 1999 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01L1/225
- WIPO fieldMeasurement
- WIPO sectorInstruments
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.