Method and apparatus for sensing a measurand
AssigneeThe Foxboro Company
InventorsAnthony C. Gilby, Dale E. Ihnat
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Abstract
Vibrating resonant mechanical structures are excited optically by photokinetic energy transfer and detected optically. In particular, a tuning fork sensor measuring a physical parameter is excited into oscillation by radiant energy and the frequency of vibration is detected by radiant energy which may be communicated via an optical fiber. These vibrations are communicated via a fiber optic to a detection location.
Claims27
Apparatus for use in the measurement of a physical parameter by photokinetic stimulation and optical detection of resonant mechanical structures, comprising:
- (a) resonant mechanical structure means for vibration;
- (b) means for communicating the physical parameter to said resonant mechanical structure means;
- (c) radiant energy source means for providing at least one radiant energy beam;
- (d) radiant energy pathway means for communicating said radiant energy to a first area of said resonant mechanical structure;
- (e) means for directly converting said radiant energy to thermal energy conducted within at least a portion of the resonant mechanical structure to stimulate motion thereof at a frequency related to the physical parameter value;
- and
- (f) means for returning at least a portion of the radiant energy along at least a portion of said pathway means as a modulated signal related to the resonant structure vibration.
A method for the photokinetic stimulation and optical detection of a resonant mechanical structure sensing at least one physical parameter, comprising the steps of:
- (a) generation of radiant energy from at least one first radiant energy source;
- (b) communicating said radiant energy along at least one radiant energy communicating pathway to a resonant mechanical structure;
- (c) converting at least a portion of the radiant energy to thermal energy;
- (d) dispersing the thermal energy within a portion of the resonant mechanical structure as stress to excite vibration of the resonant mechanical structure;
- (e) altering the frequency of the resonant mechanical structure as a function of the measured physical parameter;
- (f) modulating a portion of the radiant energy according to the frequency of vibration;
- (g) returning at least a portion of the radiant energy along said radiant energy communicating pathway as a modulated sense signal;
- and
- (h) detecting said modulated sense signal to provide a signal related to the physical parameter.
Dependencies are inferred from the claim text.