Abstract: A linear actuator includes a casing that contains a moveable shaft moved by a motor in response to a drive signal and coupled to an encoder that determines an actual instantaneous position of the shaft and forms part of a control loop that adjusts the drive signal so as to ensure accurate positioning of the shaft. A temperature sensor mounted on the shaft produces a temperature signal indicative of instantaneously measured temperature, and a temperature compensator responsive to the measured temperature for generating a negative or positive offset for correcting the drive signal so as to move the shaft to a positon that is corrected for instantaneous expansion or contraction of the shaft owing to departures of the shaft's actual temperature from a known baseline temperature.

Abstract: A sealed linear encoder includes a housing adapted for attachment to a first object and a scale unit and scanning unit arranged in a hollow body of the housing, which has a slot extending in a direction of measurement. The scanning unit is mounted on a first end of a pedestal slidably accommodated within the slot and whose second end is adapted for attachment to a second object. The slot is sealed by first and second pairs of sealing lips, which together with the pedestal are configured such that the pedestal intersects the first and second pairs of sealing lips at respective locations that are axially displaced along the direction of measurement such that there is no axial overlap between the first and second pairs of sealing lips at these locations.