Abstract: A transmitter (1) is connected to a source of DC voltage via supply wires (55) and to a sensor (53) having definable characteristics for electrical measurement of a physical variable, the transmitter having a housing (3) having terminals (18) for connection to the supply wires and containing transmitter circuitry (14, 27, 29) operable to modulate current in the supply wires to thereby transmit a signal representative of the sensed value of the physical variable; the transmitter circuitry including a microprocessor (27) and a memory for containing data defining a transfer characteristic to be operated by the microprocessor so that the signal is representative of the sensed value or of a predetermined function of the sensed value for said characteristics of the sensor; the transmitter further including an inductive loop for receiving signals relating to said data defining the transfer characteristic from an electronic programming device (20) and circuitry to load said data into the memory in response to the sig

Abstract: In a method of analyzing a spectrally modulated light signal received from an interferometric transducer the value of an optical path difference associated with a parameter to be remotely sensed is encoded as a characteristic frequency of spectral modulation in the received light. The intensity of the received light is measured at a number of wavelengths within a selected range of wavelengths to obtain data defining a measured spectrum. Reference data is generated to represent a theoretical spectrum corresponding to a nominal optical path difference, the reference data being generated for a greater range of wavelengths than the selected range of wavelengths of the measured spectrum.

Abstract: Displacement measurement apparatus (1) shown in FIG. 1 measures the position of a reading means (4) relative to a coded track (2) which carries a sequence of code elements (5). The track is encoded with a binary sequence such that reading a binary word at any position along the track uniquely identifies its position. The binary word is remotely sensed by a decoding means (18) via a fibre optic link (12). Position information is encoded optically by the reading means using an interferometer to frequency modulate the transmitted light and the decoding means has a second interferometer to analyse received light and produce an electrical output representing the binary word.

Abstract: The circuit includes a loop (3) in which a signal current flows; a supply voltage generation circuit (1); a signal conversion circuit (2); a switch (5) operative to connect either the supply voltage generation circuit or the signal conversion circuit into the loop (3) at any instant, the outputs of the supply voltage generation circuit and the signal conversion circuit being supplied to a common load (4) which controls operation of the switch (5); and a pair of capacitors (6,7) connected across the outputs of the supply voltage generation circuit and the signal current conversion circuit, respectively.

Abstract: An optical sensor comprises a plurality of light-sensitive members (10) each having an individually associated capacitor (11) which is charged with a current dependent upon the incident light sensed by the associated light-sensitive member (10); a light pulse source (12) providing light pulses from which the incident light is derived; and a control pulse source (14) providing pairs of consecutive pulses sandwiching the light pulses from the light pulse source (12), the first of which serves to discharge the capacitors (11) to a reference level prior to issue of a pulse by the light pulse source (12) and the second of which serves to effect read out from the capacitors (11) of the charge thereon deriving from the incident light from the preceding light pulse from the light pulse source (12), whereby the output of the sensor is not swamped by any stray charge on the capacitors (11).

Abstract: The invention relates to a deployable probe for measuring fluid pressures such as pitot and/or static pressure. The probe comprises an outer tubular casing, a probe member telescopically extendible from within the outer casing, spring means urging the probe member to extend longitudinally from an undeployed position which is wholly contained within the outer casing, a latch retaining the probe member in the undeployed position and releasable to deploy the probe, and extendible communicating means interconnecting the probe member and the outer tubular casing for supplying pressure indications from the probe member when the probe is deployed.

Abstract: Air data measurement apparatus for use on an aircraft, comprises a housing (1) open at both ends (2, 3) and divided into two chambers (8, 9) by a transverse wall (7). The leading end chamber (8) contains a total pressure sensor (11) and the trailing end chamber (9) contains a total temperature sensor assembly (15) whereby the apparatus functions to measure total temperature and pressure at a common point on an aircraft.

Abstract: An optical displacement sensor has an optically detectable coded track movable relative to a mask. The track is illuminated by light conducted by an optical fibre from a remote light source and the image of the track is focussed by a mirror on to the aperture of a second fibre. The mirror is mechanically movable to scan the image of the code over the fibre end to produce light pulses in the fiber which can be decoded at a remote receiver. The mirror is actuated electrically by electric energy from a photo-voltaic cell illuminated by light from a third fiber. Bits in the coded track are only partially opaque but the mask is fully opaque so the edges of the mask can be recognized by the receiver as the mirror is scanned.

Abstract: A displacement sensor employs a light conducting member containing a fluorescent material. A source of irradiating light is movable relative to the light conducting member along a track. The irradiating light produces fluorescence within the member at a corresponding position. Light from the fluorescent point is conducted in both directions along the member and can thus be collected at one end for feeding to a photo detector. By monitoring variations in the intensity of light at the detector, the distance of the fluorescent point from the end of the member can be measured, and thus movement of the source along the track monitored. Additional embodiments enable dependency on the intensity of the irradiating light source and on losses between the light conducting member and the photo detector, to be mathematically eliminated.