There is provided a linear displacement measuring apparatus which notifies a user when being installed defectively. A slider includes a traveling body which travels along a main scale on the main scale, a carriage part mounted on an object, and coupling means which couples the traveling body with the carriage part. The coupling means allows relative displacement between the traveling body and the carriage part and biases the traveling body towards the main scale. The coupling means has a connecting rod arranged so as to couple the traveling body with the carriage part via a ball joint. The slider further has misalignment detecting means which detects that the relative displacement between the traveling body and the carriage part exceeds a prescribed allowable range. The misalignment detecting means is a pair of projecting pieces arranged in a vicinity of the connecting rod so that the displacement of the connecting rod is regulated within a predetermined range.

Disclosed herein are apparatus and methods for linear actuators that can deliver strokes and forces at different values. The linear actuators include both multi-coil and single-coil actuator designs. The linear actuators include a controller that is removably or permanently coupled to a piston assembly having any number of coils. An encoder may also be removably or permanently coupled to the piston assembly. The piston assembly, controller and encoder move as one unit during actuation of the linear actuator.

A parallel plate measurement apparatus for measuring battery thickness includes a stationary bottom plate and a dynamic top plate fixed in a parallel orientation relative to the stationary bottom plate. The dynamic top plate is adapted to slide linearly along a first rail bearing in a direction perpendicular to the stationary bottom plate, and the system further includes a counterweight adapted to slide linearly along a second rail bearing in the direction perpendicular to the stationary bottom plate. Additionally, the parallel plate measurement apparatus further includes a pivot arm with a first end flexibly coupled to the dynamic top plate and a second end flexibly coupled to a counterweight. The pivot arm is adapted to rotate about a pivot bearing to apply directionally-opposing forces to the counterweight and dynamic top plate that, in turn, impart movement on the counterweight and the dynamic top plate that is constrained by the first rail bearing and the second rail bearing. The system still further includes a linear encoder adapted to measure a separation between the stationary bottom plate and the dynamic top plate.

A linear rotary encoder includes a pair of rotational surfaces. A contact belt has a first end coupled to a first rotational surface in the pair and a second end coupled to a second rotational surface in the pair. The contact belt is driven to rotate around the pair of rotational surfaces by a driving force applied to media to move the media from the first end toward the second end. An encoding scale is coupled to an inner surface of the contact belt. A reader is positioned to read the encoding scale as the contact belt rotates around the pair of rotational surfaces. The reader generates an output signal indicating a position of the media based on reading of the encoding scale.