Abstract
A method to determine a temperature of a product, the method includes: determining a dielectric constant as a function of a core-, surface-, and/or average-temperature correlation (T) of at least one product and storing the dielectric constant in a computer means; locating the product between a microwave-radiometry-antenna and a microwave-radiometry-receiver and measuring the dielectric properties of the product; selecting the correlation (T) that corresponds to the product whose dielectric properties have been measured, and calculating the core-, surface-, and/or average-temperature of the product using the dielectric constant correlation (T).
Claims
1. A method to determine a temperature of a product, comprising steps of: determining a correlation ((T)) between a dielectric constant of the product as a function of a core-, surface-, and/or average-temperature of the product and storing the determined correlation ((T)) in a computer means; heating the product in an oven; transporting the product by a conveyor from the oven towards a container; dropping the product from the conveyor into the container located below the conveyor along a free fall path; during the free fall path and before the product falls into the container, locating the product between a microwave-radiometry-antenna and a microwave-radiometry-receiver and measuring the dielectric constant of the product, the microwave-radiometry-antenna and the microwave-radiometry-receiver being located below the conveyor and above the container; selecting the determined correlation (T) from the computer means that corresponds to the product whose dielectric constant has been measured; and calculating the core-, surface-, and/or average-temperature of the product using the selected determined correlation (T).
2. The method according to claim 1, wherein the method comprises measuring a thickness of the product.
3. The method according to claim 1, wherein the core-, surface-, and/or average-temperature of the product is calculated using the selected determined correlation ((T)) and a thickness of the product.
4. The method according to claim 1, wherein an influence of the conveyor is eliminated via calibration.
5. The method according to claim 1, wherein the core-, surface-, and/or average-temperature of the product and/or moisture of a heating medium in the oven and/or heat transfer characteristics is controlled.
6. The method according to claim 1, wherein the core-, surface-, and/or average-temperature of the product is used as an initial and/or final temperature control of the oven.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The inventions are now explained according to FIGS. 1-4. These explanations do not limit the scope of protection.
(2) FIG. 1 shows the set up to measure dielectric properties.
(3) FIGS. 2, 3, and 4 show set ups to measure temperatures during production.
(4) FIG. 5 shows examples of stored data in the form of curves.
DETAILED DESCRIPTION
(5) FIG. 1 shows the set-up of the measurement of the dielectric properties .sub.r of a product 4. In the present case, the product 4 is placed between a microwave-radiometry-antenna 1 and a microwave-radiometry-receiver 3. The antenna 1 emits an electromagnetic field and the receiver 3 receives electromagnetic radiation. The receiver 3 and the antenna 1 are both connected to a microwave vector network analyzer 6 which, based on both signals and an appropriate hard- and/or software allows the determination of the dielectric properties of the product 4. The acquired data is preferably stored in computer means 7. For the determination of the dielectric properties as a function of its core-, surface-, and/or average-temperature, a certain product, whose composition and thickness is known, is placed between the antenna and the receiver and after the dielectric properties have been measured, the core-, surface-, and/or average-temperature of the product is changed and the next dielectric property for this core-, surface-, and/or average-temperature is acquired and preferably stored in the computer means 7. This procedure for different core-, surface-, and/or average-temperatures is repeated until sufficient data for correlation of the dielectric properties has been acquired. The procedure can be repeated for different products.
(6) FIG. 2 shows a first production set up. Products 4, for example patties of minced pork meat with a certain thickness have been heated in an oven to a desired core-, surface-, and/or average-temperature range. The products are transported by a conveyor, here an endless belt, and at the end of the belt the products drop along a freefall 5 into a container 9. During the freefall, the products pass the antenna 1 and the receiver 3, as described according to FIG. 1 and the dielectric properties of each product is measured and based on this measurement, its temperature is determined to assure that each product has been heated sufficiently.
(7) Regarding the embodiment according to FIG. 3, reference can be made to disclosure according to FIGS. 1 and 2. Here the measurement is done during a slide of the products along a ramp 8. Here, the ramp 8 is provided between the antenna 1 and the receiver 3. The influence of the ramp 8 on the measurement of the dielectric properties of the product 4 can be eliminated, for example by means of calibration.
(8) Regarding the embodiment according to FIG. 4, reference can be made to disclosure according to FIGS. 1 and 2. Here the measurement is done during transportation of the products with an endless belt 2. Here, the belt 2 is provided between the antenna 1 and the receiver 3. The influence of the belt on the measurement of the dielectric properties of the product 4 can be eliminated, for example by means of calibration.
(9) Regarding the embodiments of all FIGS. 1-4, the skilled person understands, that the position of the antenna 1 and the receiver 3 can be exchanged.
(10) FIG. 5 depicts the dependency of the dielectric properties .sub.r from the temperature for various products such as distilled water, cooked beef, raw beef etc. The respective curves are measured or calculated for the individual products and stored. After having received a value for the dielectric properties .sub.r and knowing the type of product that has been measured, its temperature can be derived. The curves show that even though all products mainly consist of water, the density, the composition and the structure of the product has a significant influence on the determined temperature at the same dielectric properties .sub.r values, particularly at higher temperatures.
LIST OF REFERENCE SIGNS
(11) 1 microwave-radiometry-antenna 2 Transportation means, belt 3 microwave-radiometry-receiver 4 Product 5 Freefall 6 Microwave vector network analyzer 7 Computer means 8 Ramp 9 Container
