Abstract: The calibration of a laser caliber is described. The laser caliber uses first and second sensors to determine the distance to different sides of a sheet. A third sensor is used to determine the distance between the first and second sensors. The calibration of the first, second, and third sensors is done by positioning a test object onto the platform sensed by the third sensor. The platform is moved to multiple positions in order to calibrate the first, second and third sensors. Since the displacement of the platform moves the distance to the target of the first, second and third sensors the same amount, the sensors can be accurately calibrated for a number of different positions of the test object. A very accurate calibrating displacement measuring device such as an LVDT can be used.

Abstract: A two-dimensional position detector, in combination with dynamic z and/or flutter sensors, provides dynamic misalignment detection and correction of a measuring head, thereby allowing accurate determinations to be made of properties of a sheet material, such as basis weight.

Abstract: A device for characterizing the formation of a sheet material is described. The device comprises a formation sensor for measuring the basis weight of the sheet material as the material passes through the sensor, and signal processing circuitry which receives a basis weight signal from the formation sensor and which produces three types of outputs, which outputs characterize: (1) the magnitude of variation in the sheet basis weight; (2) the strength of the weakest portion or portions of the sheet; and (3) the size of the flocs comprising the sheet. The formation sensor includes a light pipe that is held against the sheet as the sheet moves through the sensor, and that directs a small spot of light transmitted through the sheet to a light detecting device. The magnitude of small-scale variation in the sheet basis weight is computed by determining the ratio between average value of the basis weight signal and the varying or AC component of the basis weight signal.