EDDY CURRENT THERMOMETER

• US 20110090937A1
• Filed: 10/14/2010
• Published: 04/21/2011
• Est. Priority Date: 10/19/2009
• Status: Active Grant

• Current Assignee: TSI Technolocies, LLC
• Original Assignee: TSI Technolocies, LLC
• Inventors: MALYSHEV, Vladimir, Sorkine, Evgeni
• Granted Patent: US 8,523,429 B2
• Time in Patent Office: Days
• US Class Current: 374/163
• CPC Class Codes: G01K 2207/02 for measuring food temperature
• CPC Class Codes: G01K 2207/06 for preparation purposes
• CPC Class Codes: G01K 7/36 using magnetic elements, e.g. magnets, coils magnetic elements per se H01F
• CPC Class Codes: G01R 33/0283 in which a current or voltage is generated due to relative movement of conductor and magnetic field

Abstract

A remote, noncontact temperature determination method and apparatus is provided, which is operable to determine the temperature of a conducting member forming a part of or in operative thermal communication with an object of interest. The method comprises the steps of first inducing a closed vortex eddy current (28) in a conducting member (16, 38, 44) by subjecting the member (16, 38, 44) to a magnetic field, such that the corresponding eddy current magnitude changes exponentially over time. A characteristic time constant of the exponential current magnitude changes is then determined, and this is used to calculate the temperature of the object. The apparatus (24) includes a field transmitting coil (14) coupled with a waveform generator (12) for inducing the eddy current (28), and a field receiving coil assembly (18) which detects the corresponding magnetic field induced by the eddy current (28). Using the invention, temperature determinations can be made which are substantially independent of the relative distance and/or angular orientation between the conducting member (16, 38, 44) and the field receiving coil assembly (18).

Claims

1. A method of determining the temperature of an object, comprising the steps of

inducing an eddy current in a conducting member forming a part of or in operative thermal communication with said object,

said eddy current induced by subjecting said conducting member to a magnetic field having a magnitude which varies substantially linearly over time, such that the corresponding eddy current magnitude changes exponentially over time;

determining a characteristic time constant of said current magnitude changes; and

calculating the temperature of said object using said characteristic time constant.

2. The method of claim 1, including the step of using a magnetic field transmitting coil to subject said member to said magnetic field.

3. The method of claim 2, including the step of driving said transmitting coil with a triangular waveform alternating current.

4. The method of claim 1, including the steps of using a receiving coil assembly to detect said corresponding eddy current-induced magnetic field, and using the output voltage of the receiving coil assembly to determine said characteristic time constant.

5. The method of claim 4, said receiving coil assembly comprising a pair of receiving coils in electrical series but of opposite phases.

6. The method of claim 1, said characteristic time constant being the average of a plurality of time constants determined over time.

7. Apparatus for determining the temperature of an object having a conducting member forming a part of or in operative thermal communication with the object, said apparatus comprising:

a first assembly operable to induce an eddy current in said member, the magnitude of said eddy current changing exponentially over time; and

a second assembly operable to determine a characteristic time constant of said eddy current magnitude changes, and to calculate the temperature of said object using said characteristic time constant.

8. The apparatus of claim 7, said first assembly comprising a magnetic field transmitting coil operable to generate an alternating magnetic field which alternates at a substantially linear rate.

10. The apparatus of claim 7, said second assembly comprising a receiving coil assembly operable to detect said corresponding magnetic field induced by said eddy current.

11. The apparatus of claim 10, said receiving coil assembly comprising a pair of receiving coils in electrical series but of opposite phases.

12. The apparatus of claim 7, said first assembly comprising a magnetic field transmitting coil operable to generate an alternating magnetic field which alternates at a substantially linear rate, said second assembly comprising a receiving coil assembly operable to detect the corresponding magnetic field induced by said eddy current, said second assembly comprising a pair of receiving coils in electrical series but of opposite phases, said pair of receiving coils respectively located on opposite sides of said transmitting coil.

13. The apparatus of claim 7, said member being separable from said object.

9. The apparatus of 8, including a current generator operatively coupled with said magnetic field transmitting coil which drives the transmitting coil using a triangular waveform current.

14. Apparatus for determining the temperature of a food material during heating thereof, comprising:

a heating vessel operable to hold said food material and presenting a bottom wall;

a metallic conducting member positioned on said bottom wall;

a first assembly operable to induce an eddy current in said member, the magnitude of said eddy current changing exponentially over time; and

a second assembly operable to determine a characteristic time constant of said eddy current magnitude changes, and to calculate the temperature of said conducting member, and therefore the temperature of said food material, using said characteristic time constant.

15. The apparatus of claim 14, said conducting member formed of aluminum.

16. The apparatus of claim 14, said conducting member positioned inside of said pan and resting upon said bottom wall, said member having a portion projecting into said food material.

17. The apparatus of claim 16, said conducting member being separable from said bottom wall.

18. The apparatus of claim 16, said conducting member being of conical configuration, with the bottom wall of the conducting member engaging said vessel bottom wall.