Method and apparatus for rapid temperature measurement

• US 8,517,602 B2
• Filed: 04/28/2008
• Issued: 08/27/2013
• Est. Priority Date: 05/03/2007
• Status: Active Grant

• Current Assignee: Renishaw PLC
• Original Assignee: Renishaw PLC
• Inventors: Courtois, Christian
• Primary Examiner(s): Jagan, Mirellys
• Application Number:
  US12/451,127
• Publication Number:
  US 20100118913A1
• Time in Patent Office: 1,947 Days
• Field of Search: 374/112, 374/137, 374/166, 374/1, 374/110
• US Class Current: 374/112
• CPC Class Codes: G01K 15/00 Testing or calibrating of thermometers
• CPC Class Codes: G01K 7/42 Circuits effecting compensation of thermal inertia; Circuits for predicting the stationary value of a temperature

Abstract

A method of using a temperature sensor to determine the temperature of an object is described. The method comprises bringing the temperature sensor into thermal contact with the object to be measured. The temperature sensor is then used to acquire a plurality of temperature readings, the plurality of temperature readings being acquired prior to the temperature sensor reaching thermal equilibrium with the object. At least some of the plurality of temperature readings are then used to determine a pseudo-stable temperature at which the rate of change of temperature readings with time is less than a predetermined rate. The actual temperature of the object may then be predicted from the pseudo-stable temperature.

Claims

1. A method of using a temperature sensor to determine the temperature of an object, comprising the steps of:

(i) determining a start temperature, said start temperature being the temperature of the temperature sensor prior to thermal contact being established with the object;

(ii) bringing the temperature sensor into thermal contact with the object to be measured;

(iii) using the temperature sensor to acquire a plurality of temperature readings, said plurality of temperature readings being acquired prior to the temperature sensor reaching thermal equilibrium with the object;

(iv) using at least some of the plurality of temperature readings of step (iii) to determine a pseudo-stable temperature at which the rate of change of temperature readings with time is less than a predetermined rate; and

(v) determining a difference in temperature between the pseudo-stable temperature of step (iv) and the start temperature of step (i) and using said difference in temperature to predict the temperature of the object.

2. The method according to claim 1, wherein steps (iii) and (iv) are performed in parallel such that said temperature readings are monitored while being acquired to determine when the pseudo-stable temperature is reached.

3. The method according to claim 1, wherein the method is performed by a temperature sensor having a low thermal mass.

4. The method according to claim 1, wherein step (ii) comprises using a machine to bring a temperature probe comprising the temperature sensor into contact with the object.

5. The method according to claim 1, wherein step (v) comprises predicting the temperature of the object by applying a correction to the pseudo-stable temperature, wherein the applied correction depends on the difference in temperature.

6. The method according to claim 5, in which a look-up table is provided that comprises a plurality of predetermined corrections for a plurality of difference in temperatures, wherein said applied correction is determined by reference to the look-up table.

7. The method according to claim 6, further comprising taking at least two of said predetermined corrections and using an interpolation process to calculate the correction that is applied to the pseudo-stable temperature.

8. The method according to claim 6, further comprising an initial calibration routine for determining said look-up table.

9. A temperature sensing apparatus comprising a temperature sensor for acquiring a series of temperature readings and a processor for monitoring said series of temperature readings, wherein the processor is configured to:

determine a start temperature comprising a temperature of the temperature sensor prior to thermal contact being established with an object;

monitor the temperature readings acquired after the temperature sensor contacts the object;

determine when a pseudo-stable temperature is reached at which the temperature readings vary with time but at less than a predetermined rate;

determine a difference in temperature between the pseudo-stable temperature and the start temperature; and

predict the temperature of the object using the difference in temperature.

10. The apparatus according to claim 9, wherein the processor is arranged to predict the temperature of the object by applying a correction to the pseudo-stable temperature, wherein the applied correction depends on the difference in temperature.

11. The apparatus according to claim 10, in which the apparatus stores a look-up table that comprises a plurality of predetermined corrections for a plurality of difference in temperatures, wherein said applied correction is determined by the processor by reference to the look-up table.

12. The apparatus according to claim 11, wherein the processor is arranged to take at least two of said predetermined corrections and use an interpolation process to calculate the correction that is applied to the pseudo-stable temperature.

13. The apparatus according to claim 9, further comprising a temperature measurement probe in which the temperature sensor is housed.

14. The apparatus according to claim 13, wherein the processor is also located within the measurement probe.

15. The apparatus according to claim 13, further comprising an interface, wherein the processor is located in the interface and, in use, temperature readings are passed from the measurement probe to the interface.