Abstract: One or more electrostatic sensors 3 and a tacho generator 2 are provided in a machine 1 such as a gearbox. Signals from the sensors 3 and the tacho generator 2 are processed by a signal processing circuit 6 to monitor for abnormal interaction between plural interacting components of the machine 1. The signal from the tacho generator 2 may be used by the signal processing circuit 6 to produce a signal which is an average of the electrostatic activity at the interacting components over a cycle of the machine. Such an averaged signal will contain enhanced components relating to electrostatic activity relating to the cycle of the machine.

Abstract: An apparatus for monitoring a lubricant in a machine comprises sensors S1, S2 for producing signals representing electrostatic activity in a machine lubricant and a temperature sensor for producing a signal representative of the temperature of the lubricant. A signal processor 9 is arranged to process the signals from the sensors S1, S2 to detect an electrostatic activity precursor indicative of an impending wear event in the machine. The signal processor is arranged to operate in response to the temperature sensor to compensate for temperature related changes to the signals from the electrostatic sensors S1, S2.

Abstract: An optical tracker system comprises an optical sensor 1 and associated signal processing circuitry 12, 24 for conditioning signals output from the sensor and rejecting signal indicative of false sensor information. A signal rejection circuit 24 comprises a guard time monostable 28 arranged to generate a guard time pulse defining a guard time when a pulse is input from the sensor 1, an output monostable 35 arranged to generate an output pulse in response to the guard time pulse, and an output suppress monostable 30 arranged to suppress the output monostable 35 when a false signal condition occurs during the guard time.

Abstract: An amplifier circuit (1) is arranged to amplify a signal of variable magnitude from a photodiode (3) having capacitive characteristics. The circuit (1) comprises a first feedback path containing a voltage controlled variable resistor (8) for varying the gain of the amplifier in relation to the magnitude of the signal so as to provide an output signal of substantially uniform magnitude. The first feedback path also contains a capacitor (7) which compensates for adverse effects of reactance in the circuit caused by the capacitance of the photodiode (3) and of the variable resistor (8) in order to optimize the frequency response characteristics of the amplifier. A second feedback path comprising a fixed value resistor (9) becomes operable when the resistance of the first feedback path is large to provide fixed gain amplification of signals received from the photodiode (3).

Abstract: A sensor installable within a gas turbine engine for sensing electrostatic charge therein. The sensor comprises a sensing plate and first and second shielding plates. The sensing plate has a first face with a first peripheral portion, and a second face with a second peripheral portion. The first and second shielding plates are spaced from and positioned relative to the first and second faces of the sensing plate, respectively, by a layer of electrically insulating material, so that electrostatic charge in the proximity of the sensor is sensed by both the first and second peripheral portions of the sensing plate.

Abstract: An apparatus for tracking a rotating blade to determine parameters associated with the rotation of that blade. In one embodiment, the apparatus includes a detector in which at least two sensing photodiodes define substantially fan shaped detector planes and are arranged to sense an illuminated point at a known location on the blade passing through these planes. The time taken for the point on the blade to pass between the planes is measured and parameters associated with the rotation of the blade are calculated therefrom. In another embodiment, the detector defines at least two divergent detector fields, and a reactive radiation source responsive to the passage of the blade through the detector fields is provided on the blade. The reactive radiation source is arranged to radiate a signal such as a light signal which is detected by the detector.

Abstract: This invention relates to apparatus for producing a periodic output signal having a predetermined period ratio (a/b) relative to a periodic input signal.Signals from a tachometer on a gearbox are received by a counter timer unit, the counter timer unit evaluates the number of clock pulses k.sup.o received from a clock within each period of the tacho signal. A control unit receives values of k.sup.o from the counter timer and employs an algorithm based on the following equation to calculate a count value n.sup.o to be loaded into a register for the next tacho period. ##EQU1## where dK represents k.sup.-1 -k.sup.o. An accumulator is connected via an adder to the register and at receipt of each clock pulse from the clock adds the count stored in register into the accumulator. An output is produced on line when the accumulator overflows.

Abstract: The invention described in this specification relates to apparatus for monitoring the intake of foreign bodies and objects into an engine, particularly a gas turbine engine whereby sensors are located at or near the engine intake for detecting any electrostatic charge induced on the sensors by the passage of foreign bodies therepast. The specification particularly discloses an arrangement for a gas turbine engine in which sensors are provided in the exhaust duct and in the inlet duct and that signals from sensors in the inlet duct and exhaust duct are compared and contrasted.

Abstract: The present invention relates to a detector for a blade tracking system. The detector comprises a lens for focusing in a plane a bundle of radiation passing therethrough. Two or more radiation sensors are disposed within the plane, in such an arrangement that an object passing through the radiation bundle is sensed sequentially by the sensors.