Measuring apparatus for overall dimension of cold forming sectional steel and measuring method thereof

The invention relates to a measuring apparatus for an overall dimension of a cold forming sectional steel and a measuring method thereof. The technical scheme is characterized in that the apparatus is formed by an annular gear ring (3), positioning wheels or positioning gear wheels (4), a reflection type laser displacement sensor (5), and a small drive gear (1). The structure of the annular gear ring (3) is characterized in that an outer ring (8) and an inner ring (7) are fixedly connected by a concentric way by rib plates (6); a large annular gear (9) is embedded in the outer ring (8) by a concentric way; or the large annular gear (9) is directly and fixedly connected with the inner ring (7) by a concentric way by the rib plates (6). The reflection type laser displacement sensor (5) is fixed at the reflection type laser displacement sensor (5); and the emitted light of the reflection type laser displacement sensor (5) passes through center of a pitch circle. A stepping motor or a servo motor is engaged with the large annular gear (9) by the small drive gear (1); and the positioning wheels or positioning gear wheels (4) are symmetrically installed at the external circle of the annular gear ring (3). According to the invention, the provided measuring apparatus had the characteristics of simple structure, convenient operation, and high work efficiency. Moreover, the measurement is accurate and the measurement error is less than 0.1mm.