| 摘要 |
The system comprises two parallel, longitudinal rows (R1, R2) of spaced-apart marks (M) arranged on the outer surface of the rod (R) at the same intervals (x) in the two rows (R1, R2), the marks (M) of one row (R1, R2) being offset longitudinally relative to those of the other row (R2, R1) and each mark longitudinally overlapping one end of a mark (M) of the other row (R2, R1), and a first and a second detector (D1, D2) for detecting the marks (M), disposed in respective stationary positions relative to the body (B) of the cylinder (C) in the vicinity of the path followed by the first row and by the second row (R1, R2) of marks (M), respectively, so that, in operation, they can output respective periodic signals (S1, S2) the frequency (1/T) of which corresponds to the speed of movement (v) of the rod (R) relative to the body (B) of the cylinder (C) and the relative phase of which is indicative of the direction of movement of the rod (R). |
