Abstract: A compass includes a magnetic sensing element in the form of a coil surrounding magnetic material. Electric current is supplied to the coil in opposite directions, depending on the state of switches operated at times T0, for a first direction, and T5, for a reverse current direction. A voltmeter measures voltages across the coil, namely at least V1 at time T1, after T0, and V2 at time T2, after T5, with T1?T0=T2?T5=predetermined ?T. A processor indicates V1?V2, the magnitude and sign of which indicate the strength and direction of the earth's magnetic field respectively.

Abstract: A measurement device (10) comprising a sensing circuit (30) which is electrically floating and fully isolated. The sensing circuit (30) has a first (134) and a second (148) transformer across which is connected a measurement circuit (110). The device is so constructed that any signal generated in the coil (132) of the said first transformer (134) that is connected to the measurement circuit (110) caused by a change in any external magnetic field relative to the measurement circuit (110) is in anti-phase with the corresponding signal generated in the coil (164) of the said second transformer (148) that is connected to the measurement circuit (110).

Abstract: A telescopic arrangement (10) having a hollow cylinder (12) and a part (14) which is telescopically engaged with the cylinder. The arrangement is provided with at least one coil (22) constituting a first form of pulse-induction device, and at least one target (28) constituting a second form of pulse-induction device, to monitor the position of the said part (14) relative to the cylinder (12). A plurality of devices (22) each of one of the said first and second forms of device are positioned on the outside of the cylinder (12), at different respective positions therealong. At least one (28) of the other of the said first and second forms of device is fixed relative to the said part (14) of the arrangement (10) in a position such that it is moved over the said plurality of devices (22) in succession as the said part (14) is telescopically moved relative to the cylinder (12) of the arrangement (10).

Abstract: A pulse-induction displacement transducer comprising at least one coil component (100,150), at least one target (112,174), and pulse induction circuitry (102,152} constructed and arranged to cause a pulse of electrical current to pass through the said at least one coil component (100,150). The pulse ends abruptly. Subsequently, the electrical current passing through the said at least one coil component (100,150), or the voltage across it, is measured at a time when any electrical current through or voltage across the said at least one coil component (100, 150) would have died away in. the absence of a target. This provides an indication of the relative position between the target (112,174) and the said at least one coil component (100, 150). The said at least one coil component (100,150) comprises a first terminal portion (108,158), a first coil part (104,152) connected directly or indirectly to the said first terminal portion (108,158) and wound in one sense.

Abstract: A magnetic field sensor for determining the strength and/or direction of a component of an ambient magnetic field. It comprises electrical circuitry which incorporates a magnetic sensing element, a voltmeter connected in the circuitry to provide a measure of the voltage across the magnetic sensing element, an electrical energy supply connector connected to the magnetic sensing element to supply an electrical current which passes through that element when the sensor is in use, and switches to reverse the direction of the flow of electrical current through the magnetic sensing element between successive measurements of the said voltage by the said voltmeter. The magnetic sensing element comprises a coil surrounding magnetic material. The electrical energy source connector and the said switches are connected to the said coil. The voltmeter is connected to measure the voltage across the said coil.

Abstract: A telescopic arrangement (10) having a hollow cylinder (12) and a part (14) which is telescopically engaged with the cylinder. The arrangement is provided with at least one coil (22) constituting a first form of pulse-induction device, and at least one target (28) constituting a second form of pulse-induction device, to monitor the position of the said part (14) relative to the cylinder (12). A plurality of devices (22) each of one of the said first and second forms of device are positioned on the outside of the cylinder (12), at different respective positions therealong. At least one (28) of the other of the said first and second forms of device is fixed relative to the said part (14) of the arrangement (10) in a position such that it is moved over the said plurality of devices (22) in succession as the said part (14) is telescopically moved relative to the cylinder (12) of the arrangement (10).

Abstract: A measurement device (10) comprising a sensing circuit (30) which is electrically floating and fully isolated. The sensing circuit (30) has a first (134) and a second (148) transformer across which is connected a measurement circuit (110). The device is so constructed that any signal generated in the coil (132) of the said first transformer (134) that is connected to the measurement circuit (110) caused by a change in any external magnetic field relative to the measurement circuit (110) is in anti-phase with the corresponding signal generated in the coil (164) of the said second transformer (148) that is connected to the measurement circuit (110).

Abstract: A pulse-induction displacement transducer comprising at least one coil component (100,150), at least one target (112,174), and pulse induction circuitry (102,152} constructed and arranged to cause a pulse of electrical current to pass through the said at least one coil component (100,150). The pulse ends abruptly. Subsequently, the electrical current passing through the said at least one coil component (100,150), or the voltage across it, is measured at a time when any electrical current through or voltage across the said at least one coil component (100, 150) would have died away in. the absence of a target. This provides an indication of the relative position between the target (112,174) and the said at least one coil component (100, 150). The said at least one coil component (100,150) comprises a first terminal portion (108,158), a first coil part (104,152) connected directly or indirectly to the said first terminal portion (108,158) and wound in one sense.

Abstract: A nuclear magnetic resonance flowmeter comprising at least one coil (40) of electrically conductive material through which an electrical current flows when the apparatus is in use. This generates a magnetic field in a region through which flows a fluid the flow of which is to be measured and throughout which there is a uniform weak magnetic field such as the Earth's magnetic field. Electrical circuitry (46 to 52) is connected to the said at least one coil (40) to switch on and abruptly switch off such an electrical current. There is an NMR sensor (42) connected to the electrical circuitry (46 to 52) to provide a measure of the decay in the NMR signal from nuclei within such fluid following the abrupt switching off of such an electrical current. A processor (52) of the electrical circuitry (46 to 52) is formed and/or programmed to provide a measure of the flow of such fluid from the said measure of the decay. Also, a method of measuring the flow of a fluid using such a flowmeter.

Abstract: Apparatus for measuring the time taken for sound to travel a predetermined distance, including a transmitter electroacoustic transducer for transmitting an acoustic signal, and a receiver electroacoustic transducer, spaced from the transmitter electroacoustic transducer, for receiving the transmitted acoustic signal. The apparatus has a sound reflective surface spaced from the receiver electroacoustic transducer, so the latter also receives a reflection of the acoustic signal, and timing electrical circuitry connected to the receiver electroacoustic transducer to provide a measure of the time delay between the respective receptions by the receiver electroacoustic transducer of the acoustic signal and its reflection. The invention extends to a flowmeter (10) which incorporates such apparatus and an anemometer which incorporates such apparatus. The apparatus can be adapted to measure the speed of sound. The invention extends to the corresponding methods which make use of such apparatus.

Abstract: An ultrasonic flowmeter comprising an elongate duct through which fluid flows when the flowmeter is in use. Ultrasonic transducers are arranged respectively to transmit and receive ultrasonic pulses propagated through such fluid when the flowmeter is in use. Electronic circuitry is connected to the transducers to provide a measure of the time delay between emission of an electronic pulse from one of the transducers and reception of the pulse by the other of the transducers. The circuitry is constructed to enable an output to be provided which is dependent upon that delay and which is indicative of the rate of flow of fluid through the duct. The transducers are located respectively at opposite ends of the duct and are arranged to transmit and receive ultrasonic pulses propagated through the fluid substantially parallel to the duct from one end thereof to the other.

Abstract: A position indicator device (10) comprising a first array (12) of uniformly spaced-apart pulse induction affecting targets fixed in position relative to a second array of uniformly spaced-apart pulse induction affecting targets (14). The spacing between the centres of adjacent targets of the first array (12) differs from that of the second (14). The device further comprises a first set (18) of pulse-induction coils comprising a plurality of such coils and a second set (20) of pulse-induction coils comprising a plurality of such coils. The coils of the first set (18) are fixed relative to those of the second set (20). Those of the first set (18) are located adjacent to the first array (12) of targets. Those of the second set (20) are located adjacent to the second array (14) of targets. The targets (the said first and second arrays together) and the coils (the said first and second sets together) are movable relative to one another.

Abstract: An ultrasonic flowmeter comprising an elongate duct through which fluid flows when the flowmeter is in use. Ultrasonic transducers are arranged respectively to transmit and receive ultrasonic pulses propagated through such fluid when the flowmeter is in use. Electronic circuitry is connected to the transducers to provide a measure of the time delay between emission of an electronic pulse from one of the transducers and reception of the pulse by the other of the transducers. The circuitry is constructed to enable an output to be provided which is dependent upon that delay and which is indicative of the rate of flow of fluid through the duct. The transducers are located respectively at opposite ends of the duct and are arranged to transmit and receive ultrasonic pulses propagated through the fluid substantially parallel to the duct from one end thereof to the other.

Abstract: An Otto cycle internal combustion engine (10) provided with a combustion chamber (14) and an inlet (18) and an outlet (20) with respective valves (24 and 26), and a suction passage (29) leading to the said at least one inlet (18) to conduct the flow of fluid material thereto. The engine (10) further comprises a control valve (28) arranged upstream of the inlet valve (24) and being operable to change between a condition in which it opens the suction passage (29) and a condition in which it closes the suction passage (29). An engine operating position sensor (90) provides signals indicative of the operating position of the engine (10). There is also an engine power control (92). A variable intermediate position control signal generator (95), generates control signals at times respectively between the beginning and the end of each of a succession of inlet valve opening periods of the engine cycle.

Abstract: An Otto cycle internal combustion engine (10) provided with a combustion chamber (14) and an inlet (18) and an outlet (20) with respective valves (24 and 26), and a suction passage (29) leading to the said at least one inlet (18) to conduct the flow of fluid material thereto. The engine (10) further comprises a control valve (28) arranged upstream of the inlet valve (24) and being operable to change between a condition in which it opens the suction passage (29) and a condition in which it closes the suction passage (29). An engine operating position sensor (90) provides signals indicative of the operating position of the engine (10). There is also an engine power control (92). A variable intermediate position control signal generator (95), generates control signals at times respectively between the beginning and the end of each of a succession of inlet valve opening periods of the engine cycle.

Abstract: A micro-switch comprises at least one coil (22) of elongate electrically conductive material mounted on the support means (16). A movable actuator portion (20) of electrically conductive material is attached to the support means (16) so as to be movable against resilient means (10) of the micro-switch and so as to be adjacent to the coil (22). Pulse inductive circuitry (30, 32, 34, 36, 43a, 52, 54) is connected to the said at least one coil (22), and constructed to switch from one condition to another when the actuator portion (20) is moved against the force of the resilient means (10) beyond a predetermined threshold point as indicated by pulsoinductive monitoring effected by the pulse inductive circuitry (30, 32, 34, 36,43a, 52, 54). As a result of this construction, there are no physical contacts which are brought into and out of contact with one another to effect the change in the electrical condition of the micro-switch.

Abstract: Control apparatus comprising at least one electrically-conductive target portion (12). A position sensor (14) in the form of a pulse induction device is arranged in proximity with the said at least one electrically-conductive portion (12) to provide a signal indicative of a position attribute of that portion. Relative movement is possible between the target portion (12) and a coil portion (14a) of the position sensor (14). Control means (16) are connected to receive such a signal from the pulse induction device (14) and to respond in dependence upon that signal. The invention extends to such a position sensor (14) itself.

Abstract: A fluid flowmeter includes a conduit through which fluid flows by way of an inlet and an outlet for flow rate measurement. A first transducer transmits signals to and receives signals from a second transducer by way of the conduit. A second transducer is spaced from the first transducer along the conduit and transmits signals to and receives signals from the first transducer. A detector detects the time of flight of the signals between the transducers in order to measure the flow rate of the fluid along the conduct. A rod extends along the conduit to provide an annular flow path along which the signals are transmitted.