Digital measuring instruments

Claim 1

In a digital measuring instrument wherein a distance of a transfer unit that moves due to the rotation of a feed shaft of a machine is digitally measured, the improvement comprising: a casing; an encoder which is self-contained within said casing and which converts a rotary motion of said feed shaft into output pulse signals having a directional component; a direction discriminating circuit which is connected to said encoder for determining said directional component of said output pulse signals of said encoder; a reversible counter which is connected to said direction discriminating circuit through counter input gate circuit, said counter input gate circuit being provided between an input terminal of said reversible counter and an output terminal of said encoder; and a counter input gate automatic control means which comprises a storage means for storing a play of the feed shaft of the machine and said storage means is connected to an output of said direction discriminating circuit for incrementing or decrementing the stored play, wherein the disabling and enabling of said counter input gate circuit is determined based on the content of the play stored in said storage means and wherein said reversible counter counts said output pulses from said encoder.