Improved Temperature Measurement

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 ε(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 ε(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 ε(T).

Claims

1) A method to determine a temperature of a product, comprising steps of: determining a dielectric constant as a function of a core-, surface-, and/or average-temperature correlation ε(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 ε(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 ε(T).

2) The method according to claim 1, wherein the method comprises measuring a thickness of the product after the locating step.

3) The method according to claim 1, wherein the core-, surface-, and/or average-temperature is calculated using the correlation (ε(T)) and the thickness of the product

4) The method according to claim 1, wherein the measured product temperature will be the average temperature of the product and/or the surface temperature of the product and/or the core temperature of the product.

5) The method according to claim 1, wherein a correlation of the dielectric properties versus temperature (ε(T)) is stored in the computer means.

6) The method according to claim 1, wherein the core-, surface-, and/or average-temperature is averaged over a volume of the product.

7) The method according to claim 1, wherein the product is moving during the measurement.

8) The method according to claim 1, wherein an influence of a transportation means is eliminated via calibration.

9) A method to heat the product, wherein the core-, surface-, and/or average-temperature of the product is determined with the method according to claim 1.

10) The method according to claim 6, wherein the core-, surface-, and/or average-temperature measurement is utilized to control the heating of the product.

11) The method according to claim 7, wherein the core-, surface-, and/or average-temperature and/or moisture of a heating medium and/or heat transfer characteristics is controlled.

12) The method according to claim 6, wherein a plurality of products are transported in rows, wherein each row comprises a multitude of products.

13) The method according to claim 9, wherein the measured temperature is averaged over the multitude of products.

14) The method according to claim 1, wherein the core-, surface-, and/or average-temperature measurement is used as an initial and/or final temperature control.

15) The method according to claim 1, wherein a correlation of the dielectric properties versus temperature (ε(T)) is stored in the computer means as a table or as a curve.

16) The method according to claim 1, wherein the product is transported on a belt, sliding along a ramp, and/or free falling during the measurement.

17) The method according to claim 1, wherein a thickness of the product is measured after the locating step, the temperature is calculated using the dielectric constant correlation (ε(T)) and the thickness of the product, the product is transported on a belt, sliding along a ramp, and/or free falling, and an influence of a transportation means is eliminated via calibration.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The inventions are now explained according to FIGS. 1-4. These explanations do not limit the scope of protection.

[0029] FIG. 1 shows the set up to measure dielectric properties.

[0030] FIGS. 2, 3, and 4 show set ups to measure temperatures during production.

[0031] FIG. 5 shows examples of stored data in the form of curves.

DETAILED DESCRIPTION

[0032] FIG. 1 shows the set-up of the measurement of the dielectric properties ε.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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] FIG. 5 depicts the dependency of the dielectric properties ε.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 ε.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 ε.sub.r values, particularly at higher temperatures.

LIST OF REFERENCE SIGNS

[0038] 1 microwave-radiometry-antenna [0039] 2 Transportation means, belt [0040] 3 microwave-radiometry-receiver [0041] 4 Product [0042] 5 Freefall [0043] 6 Microwave vector network analyzer [0044] 7 Computer means [0045] 8 Ramp [0046] 9 Container