Abstract: A sensor assembly for a fastener assembly comprising a nut and a bolt comprises a sensor unit mounted in a cavity in the nut of the fastener assembly having an internal opening in the internal thread of the nut. The sensor unit comprises an optical flow sensor arranged to capture an image of the external thread of the bolt through the internal opening and to sense relative movement of the external thread of the bolt.

Abstract: There is provided a sensor unit for a fastener assembly, the sensor unit comprising a mounting arranged to rigidly attach the sensor unit to, or adjacent to, a fastener assembly; and a sensor, that is an optical flow sensor or an inductive sensor, configured to sense movement of the fastener assembly. The sensor unit may comprise a processor arranged to process the output of the sensor to detect loosening of the fastener assembly and to output a signal representing the status of the fastener assembly. The sensor unit may comprise a wireless communication unit arranged to communicate the signal.

Abstract: A wireless network comprises nodes, including routers having a tree-shaped communication topology and end devices, communicate in accordance a network protocol, wherein the routers transmit beacons in respective timeslots within a periodic beaconing interval, passively scan for messages, and, in response to receiving a message, transmit an acknowledgement thereof the received message. An end device that has a message that is pending transmission, passively scans for beacons transmitted from any router; and in response thereto, transmits the message, and passively scans for an acknowledgement, repeating those steps if no acknowledgement is received. This provides responsivity in an environment having rapidly changing propagation paths. To reduce power consumption, the end devices do not passively scan for beacons except when they have a message that is pending transmission, and also at predetermined times for reception of a downstream message.

Abstract: An elongate component such as a drill string of drill pipes connected by joint sections inside a bore is sensed using at least one set of electromagnetic coils, the coils within the set being arranged at different angular positions around the bore facing the bore. There may be at least two sets of coils separated along the axial direction of the bore. Electrical oscillations are generated in the coils to produce oscillating electromagnetic fields that interact with the contents of the bore. A parameter of the electrical oscillations generated in each coil is detected. The detected parameters may be used to derive both (1) a measure of the axial position along the bore, and (2) a measure of the lateral position. The detected parameters may be used to derive a measure of electromagnetic properties of the contents of the pipe in a region adjacent each coil, thereby imaging the contents of the pipe.

Abstract: A wireless network comprises nodes, including routers having a tree-shaped communication topology and end devices, communicate in accordance a network protocol, wherein the routers transmit beacons in respective timeslots within a periodic beaconing interval, passively scan for messages, and, in response to receiving a message, transmit an acknowledgement thereof the received message. An end device that has a message that is pending transmission, passively scans for beacons transmitted from any router; and in response thereto, transmits the message, and passively scans for an acknowledgement, repeating those steps if no acknowledgement is received. This provides responsivity in an environment having rapidly changing propagation paths. To reduce power consumption, the end devices do not passively scan for beacons except when they have a message that is pending transmission, and also at predetermined times for reception of a downstream message.

Abstract: A sensor system comprises a marginal oscillator. A tank circuit comprises inductive and capacitive elements including a probe arranged to generate an electromagnetic field in a sensing region. A non-linear drive circuit drives oscillation of the tank circuit by supplying a differential signal pair of complementary signals across the tank circuit, sustaining the oscillation on the basis of at least one of the complementary signals. A detection circuit detects a characteristic of the oscillation of the tank circuit that is dependent on the electromagnetic properties of the contents of the sensing region and to derive a signal representing the at least one characteristic. The differential signaling provides numerous advantages, including improved accuracy and signal-to-noise.

Abstract: An elongate component such as a drill string of drill pipes connected by joint sections inside a bore is sensed using at least one set of electromagnetic coils, the coils within the set being arranged at different angular positions around the bore facing the bore. There may be at least two sets of coils separated along the axial direction of the bore. Electrical oscillations are generated in the coils to produce oscillating electromagnetic fields that interact with the contents of the bore. A parameter of the electrical oscillations generated in each coil is detected. The detected parameters may be used to derive both (1) a measure of the axial position along the bore, and (2) a measure of the lateral position. The detected parameters may be used to derive a measure of electromagnetic properties of the contents of the pipe in a region adjacent each coil, thereby imaging the contents of the pipe.

Abstract: A sensor arrangement for a rotatable element comprises two coils capable of being driven by oscillatory drive signals to generate electromagnetic fields. The coils are in different positions overlying a cylindrical portion of the rotatable element that has a target feature configured to interact with the generated electromagnetic fields when the target feature is aligned with the coils. Alignment between the target feature and the coils occurs at angular positions of the rotatable element that are offset for respective coils. Thus, by detecting a characteristic of the signals developed across the coils allowing derivation of an angular velocity signal representative of angular velocity. Also, the degree of interaction between the target feature and the electromagnetic fields varies with the axial position of the rotatable element, differentially between the coils, allowing derivation of an axial position signal representative of the axial position of the rotatable element.

Abstract: A sensor system comprises a marginal oscillator. A tank circuit comprises inductive and capacitive elements including a probe arranged to generate an electromagnetic field in a sensing region. A non-linear drive circuit drives oscillation of the tank circuit by supplying a differential signal pair of complementary signals across the tank circuit, sustaining the oscillation on the basis of at least one of the complementary signals. A detection circuit detects a characteristic of the oscillation of the tank circuit that is dependent on the electromagnetic properties of the contents of the sensing region and to derive a signal representing the at least one characteristic. The differential signaling provides numerous advantages, including improved accuracy and signal-to-noise.

Abstract: A sensor arrangement for a rotatable element comprises two coils capable of being driven by oscillatory drive signals to generate electromagnetic fields. The coils are in different positions overlying a cylindrical portion of the rotatable element that has a target feature configured to interact with the generated electromagnetic fields when the target feature is aligned with the coils. Alignment between the target feature and the coils occurs at angular positions of the rotatable element that are offset for respective coils. Thus, by detecting a characteristic of the signals developed across the coils allowing derivation of an angular velocity signal representative of angular velocity. Also, the degree of interaction between the target feature and the electromagnetic fields varies with the axial position of the rotatable element, differentially between the coils, allowing derivation of an axial position signal representative of the axial position of the rotatable element.