Apparatus for sampling a material travelling past a sampling region

Apparatus for sampling a material which travels past a sampling region, the apparatus comprising:

• sensing means arranged at spaced intervals with respect to the sampling region, the sensing means having respective sensing zones in the sampling region;
• drive means for causing relative periodic movement between at least one of said sensing means and the remaining sensing means so that, in a cycle of such movement, there is a periodic overlap of at least the sensing zones of adjacent sensing means in the sampling region due to an overlap of respective scanning paths of the sensing means, the sensing means producing monitoring signals when sensing respective adjacent portions of the material across its width, said monitoring signals representing a characteristic of the material travelling past the sampling region;
• and
• signal processing means for processing values corresponding with the monitoring signals to provide an output for monitoring changes in said characteristics,
• said sensing means including at least one primary sensing means which produces comparatively accurate monitoring signals compared with the monitoring signals produced by the other or secondary sensing means, and said signal processing means further including means for storing and comparing the monitoring signals or values corresponding thereto, which are produced where the scanning paths overlap, said processing means processing said signals or values and producing information which is utilised by processing means for calibrating the secondary sensing means with respect to the primary sensing means and the material travelling past the sampling zone.

A method of sampling material travelling past a sampling region across which a plurality of sensing means are arranged at spaced intervals, the sensing means having respective sensing zones in the sampling region, the method including the steps of causing relative periodic movement between the sensing means and the sampling region, or between at least one of the sensing means and the remaining sensing means so that, in a cycle of movement, there is a periodic overlap of at least the sensing zones of adjacent sensing means in the sampling region due to an overlap of respective scanning paths of the sensing means;

• producing monitoring signals when sensing respective adjacent portions of the travelling material across its width, the monitoring signals representing a characteristic of the travelling material;
• and processing the monitoring signals to provide an output for monitoring changes in said characteristic,
• the method further including using at least one of the sensing means as a primary sensing means for producing comparatively accurate monitoring signals compared with the monitoring signals produced by the other or secondary sensing means;
• and by storing and comparing the monitoring signals, or values corresponding thereto, which are produced where the scanning paths overlap, and producing information from said signals or values either for calibrating the secondary sensing means with respect to the primary sensing means and the material travelling past the sensing zone, or for making any one of the sensing means redundant, or both.