Abstract: A strain-free sensor includes a conductor extending from a first end to a second end through an intermediate portion. The conductor has a first coefficient of thermal expansion. A coating is bonded to the intermediate portion of the conductor. The coating has a second coefficient of thermal expansion that is distinct from the first coefficient of thermal expansion. A tube is disposed about the conductor. The tube includes an inner surface provided with a plurality of projections. The conductor is slidingly arranged within the tube with the plurality of projections being configured and disposed to establish a substantially friction-free interface between the tube and the conductor forming the strain-free sensor.

Abstract: A strain sensing cable including one or more strain sensing elements and a strain transfer medium extruded directly onto the one or more strain sensing elements disposed within the strain transfer medium. The strain transfer medium is operatively arranged to transfer strain experienced by the cable to the one or more strain sensing elements. A method of making a strain sensing cable is also included.

Abstract: A strain sensing cable including one or more strain sensing elements and a strain transfer medium extruded directly onto the one or more strain sensing elements disposed within the strain transfer medium. The strain transfer medium is operatively arranged to transfer strain experienced by the cable to the one or more strain sensing elements. A method of making a strain sensing cable is also included.

Abstract: The present invention is directed to an aquarium undergravel filter. In particular, the undergravel filter of the present invention contains chambers on its underside. The chambers, which are roughly equal in size, are separated by baffles and have openings which allow water to flow into flow channels which lead to the lift tube holes. The chambers and flow channels provide for equal filtration over the entire surface of the filter plate. In a preferred embodiment, the undergravel filter of the present invention also contains an anti-dig grid which prevents fish from digging the gravel on the plate of the filter by use of an anti-dig grid. The anti-dig grid is located on the top surface of the filter and prevents fish from removing the gravel and exposing the openings in the filter.

Abstract: A floating impeller assembly for use with an electromagnetic stator unit includes a stationary shaft with a magnetic rotor rotationally mounted on the shaft. An impeller unit is rotationally mounted on the shaft and a unitary retaining and clutch mechanism between the magnetic rotor and the impeller unit drives the impeller unit by means of rotation of the magnetic rotor. The magnetic rotor and the impeller float on the shaft facilitating reducing the noise, friction and wear, heretofore, present in prior art units. The floating impeller assembly is used within an aquarium filter for drawing water from the aquarium into the aquarium filter for filtration and discharge back into the aquarium tank.

Abstract: A rotor impeller assembly for use with an electomagnetic stator unit including a shaft with a magnetic rotor directly mounted on the shaft. An impeller unit is rotationally mounted with respect to the shaft. A clutch between the magnetic rotor and the impeller unit rotationally drives the impeller unit by means of the magnetic rotor. The magnetic rotor is formed as an injection molded magnet. The impeller unit is used within an aquarium filter for drawing water from the aquarium tank into the aquarium filter for filtration and discharge back into the aquarium tank.