A linear gauge consists of a linear gauge sensor (detector) and a digital gauge counter (display).
The linear gauge sensor has a movable slit that moves in conjunction with the spindle and a fixed slit that is fixed in a fixed position, positioned opposite each other. The slits are printed with light and dark markings at regular intervals. Since counting requires determining the direction of spindle movement (+ and - directions), the two fixed slits, A and B, are positioned such that B is offset by 1/4P (pitch) relative to A.
The light source (LED) and the light-receiving element face each other across these slits. (Figure 1)
As the moving slit moves relative to the fixed slit, the light passing through the fixed slit's window alternates between light and dark. At this time, two square wave signals with a 90° phase difference and the same period are output. The direction is determined from the phase lead or lag, and the displacement is measured by adding or subtracting these signals using a counter. (Figure 2)
The output signal of a linear gauge sensor has a pitch of 1P = 4 μm (1 μm resolution type) or a pitch of 1P = 40 μm (10 μm resolution type). However, by multiplying the signal by 4 with a digital gauge counter, a measurement resolution of 1/4 of the pitch (1 μm or 10 μm) can be obtained.
