Abstract

A hand-held tape measure is provided which includes a conveniently sized housing with an elongated measuring tape suitably coiled on a rotatable shaft mounted within said housing. A sprocket arranged to engage the surface of the tape without slippage is mounted within the housing and drivingly connected to an encoding disk whereby the rotation of the disk is directly proportional to the linear movement of the free end of the tape. The disk is divided into an equal number of alternating transparent and opaque segments and two energy sensitive coupler switches are mounted in conjunction with the disk to provide electrical outputs indicative of the adjacent disk segment to indicate the rotation of the disk. The switches are offset circumferentially to provide a phase differential which indicates whether the tape is extending or retracting with respect to the housing. The output from the switches is fed to an electronic circuit which counts and divides the output pulses with the result digitally displayed. A variable speed reversible motor which is powered by an internal power source can be drivingly connected to the tape to control its movement. A switch is provided on the housing for controlling the direction of the motor. This switch can also include a lock for holding the tape in the retracted position when the motor is deenergized.