Method for in-line measurement of the temperature of products travelling on a conveyor in a food processing operation

A method for determining a temperature of products transported on a conveyor belt of a cryogenic tunnel, comprising the steps of:

• (a) carrying out a continuous measurement of a surface temperature of products moving along the conveyor belt opposite a temperature measurement system, the temperature measurement system being a pyrometer and being fixed in space in a position close to, above, or to the side of, the conveyor;
• (b) measuring a thickness of one of the products, whose temperature was measured during said step (a), with a distance measurement system, the distance measurement system being a laser or an ultrasound system;
• (c) using a computer to determine whether the thickness of one of the products measured by the distance measurement system is between a lower limit and an upper limit of a range of thicknesses, wherein when the computer makes the determination that the thickness of said one of the products measured by the distance measurement system is between a lower limit and an upper limit, the computer considers that a temperature measured for said one of the products by the temperature measurement system is a default value and a reliable value for the temperature of the product;
• (d) using a computer to determine whether the thickness of said one of the products is greater than an upper limit or well below a lower limit, wherein when the computer makes the determination that the thickness of said one of the products is greater than an upper limit or well below a lower limit, the computer takes into account and stores, in memory, the last product temperature value measured by the temperature measurement system and which the computer also considers as a reliable value in said step (c), and the computer considers said last product temperature value to be a good indication of the temperature of the product whose measured thickness is outside the range of thicknesses;
• and
• (e) after a determined period of time, during which the measured thickness is outside the range of thicknesses, the computer concludes that there are no products on the conveyor, the computer no longer takes into account the temperature measurements provided by the temperature measurement system, and the computer no longer considers temperature measurements as default values.