Radiometric temperature measurement based on empirical measurements and linear functions

• US 5,967,992 A
• Filed: 06/03/1998
• Issued: 10/19/1999
• Est. Priority Date: 06/03/1998
• Status: Expired due to Fees

• Current Assignee: Trutek Corp
• Original Assignee: Trutex Incorporated
• Inventors: Canfield, Eric L.
• Primary Examiner(s): Jastrzab, Jeffrey R.
• Assistant Examiner(s): Imam, Ali M.
• Application Number:
  US09/089,374
• Time in Patent Office: 503 Days
• Field of Search: 600/474, 600/475, 600/473, 600/549, 600/559, 374/121, 374/130, 374/131, 374/133
• US Class Current: 600/474
• CPC Class Codes: G01K 7/42 Circuits effecting compensation of thermal inertia; Circuits for predicting the stationary value of a temperature

Abstract

In contrast to the non-linear systems used in certain past infrared thermometers, the present invention uses an empirical data set to determine patient temperature. The empirical data set provided by the present invention represents actually measured thermometer sensor outputs over a substantial number of target and ambient temperature points within the thermometer'"'"'s operating range. The empirical data set is collected during a testing process, and is stored in a non-volatile memory within the thermometer. At temperature measuring time, the thermometer accesses the appropriate cell in the non-volatile memory to determine temperature. The substantial size of the empirical data set eliminates guesswork and estimation--since the most accurate indication of how a thermometer will perform under certain conditions is a record of how it previously performed under those same conditions. To reduce total testing time while achieving nearly comparable accuracy, the present invention systematically collects empirical data in sufficient quantities to cover a range of reference target and ambient temperatures. To provide additional resolution, a simple linear function such as averaging (i.e., adding two collected data points and dividing by two) can be used to supply intermediate data points between the empirical points that were collected.

Claims

1. A method of developing measurement data for a tympanic thermometer comprising:

(a) systematically collecting, across a range of reference target and ambient temperatures, empirical thermometer measurement data in sufficient quantities and in such a way as to provide an empirical data set comprising a number of data points;

(b) using a linear function to supply at least one intermediate data point not collected by step (a); and

(c) combining said empirical data set with said at least one intermediate data point to provide a measurement data set for use by a tympanic thermometer to develop a temperature measurement.

2. A method as in claim 1 wherein the tympanic thermometer has a writable memory, and the method further comprises:

(d) writing said combined collected and said supplied data points into said tympanic thermometer writable memory.

3. A method as in claim 1 wherein said step (b) comprises averaging at least two collected data points to supply an intermediate data point or data points.

4. A method as in claim 1 wherein said step (a) comprises gathering on the order of at least 10% of the total data points within a thermometer'"'"'s specified operating range.

5. A method as in claim 2 wherein step (d) comprises writing said combined collected and said supplied data points into a lookup table.

6. A method of operating an ear thermometer including an infrared sensor and a temperature sensor, said infrared sensor measuring the infrared flux between said infrared sensor and a target, said temperature sensor measuring the temperature of said infrared sensor, said method comprising:

collecting and storing, within the ear thermometer, an empirical data set comprising a number of data points, each data point specifying (a) an infrared flux measured by said infrared sensor, (b) a corresponding temperature measured by said temperature sensor, and (c) a corresponding reference target temperature;

optically coupling said infrared sensor to a person'"'"'s ear;

measuring (a) the infrared flux between said infrared sensor and the person'"'"'s ear tissue, and (b) the temperature of said infrared sensor cold junction; and

accessing the collected stored empirical data set to determine the reference target temperature corresponding to said measured infrared flux and said cold junction temperature.

7. A method of operating an ear thermometer including an infrared sensor and a temperature sensor, said infrared sensor measuring the infrared flux between said infrared sensor and a subject, said temperature sensor measuring the temperature of said infrared sensor, said method comprising:

using said ear thermometer to collect an empirical data set comprising a number of data points, each data point specifying (a) an infrared flux measured by said infrared sensor, (b) a corresponding temperature measured by said temperature sensor, and (c) a corresponding reference target temperature;

storing said empirical data set in the thermometer; and

taking a person'"'"'s temperature by performing the following steps;

(1) optically coupling said infrared sensor to the person'"'"'s ear canal;

(2) measuring the infrared flux between said infrared sensor and the person'"'"'s ear tissue;

(3) measuring the temperature of said infrared sensor with said temperature sensor;

(4) accessing the stored empirical data set within the thermometer to determine the reference target temperature corresponding to said measured infrared flux and said measured infrared sensor temperature; and

(5) providing an indication of said corresponding reference target temperature as the temperature of said person.

8. A method as in claim 7 wherein said storing step comprises the step of storing at least on the order of at least 10% of the total data points within a thermometer'"'"'s specified operating range.

9. A method as in claim 7 wherein said storing step comprises storing said data points in a non-volatile randomly accessible memory.

10. A method as in claim 7 wherein said storing step comprises storing said data points in a lookup table.

11. A method as in claim 7 further including the step of correcting said indication to provide an oral equivalent temperture.

12. A method as in claim 7 further including the step of correcting said indication to provide a rectal equivalent temperture.

13. A method as in claim 7 wherein said empirical data set represents actually measured thermometer sensor outputs over a substantial number of target and ambient temperature points within the thermometer'"'"'s operating range.

14. A thermometer empirical data collection process comprising:

(a) optically coupling an individual thermometer instrument to a temperature reference target, said thermometer including an infrared sensor generating an infrared flux value Φ

_b and a temperature sensor coupled to the infrared sensor, the temperature sensor generating a value T_s indicating the temperature of said infrared sensor;

(b) placing said thermometer instrument and said temperature reference target into an environmental chamber;

(c) controlling the environmental chamber to sweep its temperature across an ambient temperature operating range;

(d) for each of several ambient temperatures within said ambient temperature operating range, acquiring a data point consisting of the two thermometer sensor outputs T_s, Φ

_b and the temperature of the temperature reference target; and

(e) storing said data points acquired by said step (d) into said thermometer for use in looking up the temperature of a subject.

15. A thermometer testing and empirical data collection method for efficiently collecting an empirical data set for use by thermometer instruments each including an infrared sensor generating an infrared flux value Φ

_b and a temperature sensor coupled to the infrared sensor, the temperature sensor generating a value T_s indicating the temperature of said infrared sensor, said method comprising;

(a) mating each individual thermometer instrument with a "black body" temperature reference target;

(b) coupling said thermometer instrument and corresponding reference target together through an electrically controllable shutter;

(c) placing said thermometer instrument and corresponding black body temperature reference target and shutter into an environmental chamber

(d) setting the temperature of the black body temperature reference target to a particular reference temperature;

(e) controlling the environmental chamber to sweep its temperature across the desired ambient temperature operating range of the thermometer;

(f) using the thermometer to control the shutter to open for a short time duration each time the thermometer'"'"'s temperature sensor senses the next incremental temperature in a sequence;

(g) each time the shutter is opened, acquiring a data point consisting of the two thermometer sensor outputs T_s, Φ

_b and the blackbody reference temperature;

(h) incrementally changing the temperature of the black body temperature reference to a new value and repeating steps (e)-(g); and

(i) repeating said step (h) until an empirical data set has been developed to cover the thermometer'"'"'s desired target temperature range.

16. A method as in claim 15 wherein said repeating step (i) includes the step of covering a thermometer target temperature range of 94°

F. to 108°

F.

17. A method as in claim 15 wherein said step (h) comprises the step of changing the temperature of the blackbody temperature reference by 0.5°

F.

18. A method as in claim 15 wherein said sweeping step includes the step of sweeping the temperature of the environmental chamber from 60.8°

F. to 104°

F.

19. A method as in claim 15 wherein said shutter opening step comprises opening said shutter for each 0.1°

F. ambient temperature increment.

20. A method as in claim 15 wherein said shutter opening step comprises opening and closing of the shutter under control by the thermometer.

21. An infrared thermometer empirical data collection system comprising:

an infrared thermometer including an infrared sensor generating an infrared flux value Φ

_b and a temperature sensor coupled to the infrared sensor, the temperature sensor generating a value T_s indicating the temperature of said infrared sensor;

an environmental chamber for holding said infrared thermometer and a temperature reference target;

means for optically coupling, within said environmental chamber, said thermometer to said temperature reference target;

means coupled to said environmental chamber for controlling the environmental chamber to sweep its temperature across an ambient temperature operating range;

means coupled to said thermometer sensors for acquiring, for each of several ambient temperatures within said ambient temperature operating range, a data point consisting of the two thermometer sensor outputs T_s, Φ

_b and the temperature of the temperature reference target; and

lookup means coupled to said acquiring means for storing said acquired data points into said thermometer for use in looking up the temperature of a subject.