Abstract: A gas valve (14) control system (10) uses a control signal (16) to enable a valve (14) and a validation signal (22) to validate the control signal (16). The system (10) includes a valve (14) connected to a burner (12). A receiver (18) is electrically connected to the valve (14) and provides the valve (14) with the control signal (16). A controller (20) has a control transmitter (24) in wireless communication with the receiver (18) to transmit the control signal (16) to the receiver (18) at a speed of light. The controller (20) further includes a validation transmitter (26) to transmit a validation signal (22) to the receiver (18) at a speed of sound. The valve (14) is enabled by the control signal (16) if a time delay between the receiver (18) receiving the control signal (16) and the validation signal (22) is shorter than a maximum delay period. The control signal (16) is discarded if the time delay is longer than the maximum delay period.

Abstract: An improved intensity-encoded fiber optic sensor incorporating novel drift correction and filtering means is disclosed. The first embodiments of the invention relate to means for removing unwanted higher-order core and cladding modes from an intensity-encoded signal in an optical fiber using mode strippers and mode filters located strategically at various points in the sensing system. The second set of improvements in the invention relate to an improved technique for long-term temporal drift cancellation in a fiber optic pressure sensor by periodically applying pressure to the sensor tip in order to ascertain the measured voltage at which the sensor diaphragm contacts other elements of the sensor. This measured voltage is subtracted from an initial calibration voltage, and the result is applied to the measured signal as a constant correction term.