Abstract: A float operated electrical switch assembly has a housing (10) fitted to an opening in a container wall (14). A float (19) follows the liquid level and is pivoted with a primary magnet (18) about a pivot axis (17). A pivotal secondary magnet (21) acts in repulsion with the primary magnet (18) through a non-magnetic wall (20) of the housing (10). The movement of the secondary magnet (21) causes at least one control rod (48) to reciprocate. A switch contact (32) is normally held under the resilience of its carrier leaf spring (38) in engagement with a fixed switch contact (33). The contacts are opened by movement of the control rod (48) moving the switch contact (32) against the resilience of its carrier.

Abstract: A high liquid level sensor comprising a tubular probe, with a peripheral wall (6), and arranged to be suspended in a liquid container. An ultrasonic signal is transmitted around the wall (6) from a transmitting transducer (12) potted in a block (11), which is bonded to the inner surface of the wall, to a receiving transducer also potted in the block. A detector circuit connected to the receiving transducer via a lead (10) discriminates between the signal level when the probe is immersed in gas and the lower signal level when the probe is immersed in liquid, and provides a corresponding switched output.

Abstract: A system for monitoring a low conductivity liquid carrying an electrostatic charge and flowing along a pipeline comprises two separately insulated conductive wall sections (M.sub.1, M.sub.3) of the pipeline one downstream of the other. Means are connected to each of these sections for providing a signal representing the relaxation current released from the liquid to each of the wall sections and these signals are processed to provide indications or controls dependent upon the conductivity of the liquid, the relaxation time of the liquid, the streaming current, or the charge density carried by the liquid.

Abstract: The invention relates to magnetically operated electric switches of the kind comprising a magnet which is pivotally mounted and is arranged to rock to and fro with a snap action under the influence of an adjacent relatively movable magnetic actuator, and at least one switch contact which is moved between two end positions relatively to one or more complementary switch contacts upon rocking of the magnet. The magnet is a bar magnet fixed in a pivoted carrier which forms one link of an over center spring toggle acting on a flexible leaf which carries the movable contact or contacts.