Abstract: Thickness measurement apparatuses 1 and 2 are set a preset distance Ld from each other. The first apparatus 1 performs calibration using a thickness reference plate 5c. While the second apparatus 2, placed on a downstream side in a conveying direction, is performing measurement process, mode setter 3 sets “measurement” for the first apparatus 1. Mode setter 3 further gives an instruction to start a “thickness correction” process to the second apparatus 2. Mode setter 3 delays a first thickness measurement value 1 until a position corresponding to the distance is reached in a traveling distance, determines the difference between the first value 1 and a second thickness measurement value 2 from the second apparatus 2 as a correction value, and executes thickness correction without halting the measurement performed by the second apparatus 2.

Abstract: Thickness measurement apparatuses 1 and 2 are set a preset distance Ld from each other. The first apparatus 1 performs calibration using a thickness reference plate 5c. While the second apparatus 2, placed on a downstream side in a conveying direction, is performing measurement process, mode setter 3 sets “measurement” for the first apparatus 1. Mode setter 3 further gives an instruction to start a “thickness correction” process to the second apparatus 2. Mode setter 3 delays a first thickness measurement value 1 until a position corresponding to the distance is reached in a traveling distance, determines the difference between the first value 1 and a second thickness measurement value 2 from the second apparatus 2 as a correction value, and executes thickness correction without halting the measurement performed by the second apparatus 2.