Electronic thermometer with fixed response time

• US 4,727,500 A
• Filed: 05/01/1985
• Issued: 02/23/1988
• Est. Priority Date: 05/01/1985
• Status: Expired due to Term

• Current Assignee: Sherwood Services AG
• Original Assignee: Sherwood Medical Company (Medtronic Plc)
• Inventors: Burger, Laurie J., Jackson, Edward W.
• Primary Examiner(s): Krass, Errol A.
• Assistant Examiner(s): Teska, Kevin J.
• Application Number:
  US06/729,046
• Time in Patent Office: 1,028 Days
• Field of Search: 364/415, 364/557, 364/577, 374/102, 374/169, 374/170, 128/736
• US Class Current: 702/131
• CPC Class Codes: G01K 7/42 Circuits effecting compensation of thermal inertia; Circuits for predicting the stationary value of a temperature

Abstract

An electronic thermometer includes a temperature sensitive element and a programmable microcomputer coupled to receive temperature data from the element. After processing the data in accordance with a control program, a predicted temperature is provided on a display. The program includes instructions causing a microcomputer to store temperature data at selected intervals during a fixed duration sampling period. A computation algorithm is then selected from a high ambient temperature algorithm, a normal ambient temperature algorithm, and a low ambient temperature algorithm, and the body temperature computed using one of the selected algorithms. The thermometer also displays operator error if the temperature sensing element senses a decrease in temperature during the fixed duration sampling period.

Claims

1. An electronic thermometer, comprising:

a temperature sensing element;

a programmable microcomputer electronically connected to receive temperature data from said sensing element and electronically connected to enable it to provide an output to a display; and

a control program for computing the temperature of a body in thermal contact with said sensing element from said temperature data, said program including instructions which cause said microcomputer to store temperature data at selected time intervals during a fixed duration sampling period, to select a computation algorithm from a high ambient temperature algorithm, a normal ambient temperature algorithm, and a low ambient temperature algorithm according to the values of said stored temperature data, to compute said body temperature using said selected algorithm and said stored temperature data, and to provide an output to said display representing said computed body temperature.

2. An electronic thermometer as defined in claim 1, wherein the program selects the high temperature algorithm when the difference between said temperature data at selected pairs of said time intervals is less than a preselected value.

3. An electronic thermometer as defined in claim 1, wherein the program selects the low temperature algorithm when the temperature data at a selected one of said time intervals is less than a preselected value.

4. An electronic thermometer as defined in claim 1, wherein the program selects the high temperature algorithm when the difference between the temperature data at selected pairs of said time intervals is less than a selected value, the program selects the low temperature algorithm when the temperature data at a selected one of said time intervals is less than a selected value, and the program selects the normal temperature algorithm when neither of the high and low temperature algorithms are selected.

5. An electronic thermometer as defined in claim 1, wherein the high temperature algorithm is:

space="preserve" listing-type="equation">T.sub.F =T.sub.20 *K1+COR

space="preserve" listing-type="equation">COR=(T.sub.0 -T.sub.5)/K2 IF T.sub.0 -T.sub.5 is less than K.sub.3

space="preserve" listing-type="equation">ELSE COR=0

where;

T_F =computed temperature;

T₀ =probe temperature data initially

T₅ =probe temperature data at five seconds

T₂₀ =probe temperature data at twenty seconds and K1, K2 and K3 are constants selected for accurate temperature computation;

the normal temperature algorithm is;

space="preserve" listing-type="equation">T.sub.F =T.sub.20 /(1-EXP. TIME.sub.1)+T.sub.25 /(1-EXP. TIME.sub.2))/2+COR

where;

space="preserve" listing-type="equation">TIME.sub.1 =-K6/((T.sub.20 -T.sub.15)/(T.sub.15 -T.sub.10)*K7)

space="preserve" listing-type="equation">TIME.sub.2 =K8/((T.sub.25 -T.sub.20)/(T.sub.20 -T.sub.15)*K9)

space="preserve" listing-type="equation">COR=(T.sub.0 K10-T.sub.5)*K11, IF (T.sub.0 -K12-T.sub.5) 0

space="preserve" listing-type="equation">ELSE;

COR=(T.sub.0 -K13-T.sub.5)*K14,

space="preserve" listing-type="equation">AND;

COR=-COR, IF 0 COR K15

T_F =computed temperature

T₀ =probe temperature data initially

T₅ =probe temperature data at five seconds

T₁₀ =probe temperature data at ten seconds

T₁₅ =probe temperature data at fifteen seconds

T₂₀ =probe temperature data at twenty seconds

T₂₅ =probe temperature data at twenty-five seconds

K6, K7, K8, K9, K10, K12, K13, K14 and K15 are constants selected for accurate temperature computation;

EXP. TIME₁ and EXP. TIME₂ are exponential times for TIME₁ and TIME₂ as defined; and

the low temperature algorithm is;

space="preserve" listing-type="equation">T.sub.F =(T.sub.25 *K4)-(T.sub.10 -K5)

where;

T₂₅ =probe temperature data at twenty-five seconds

T₁₀ =probe temperature data at ten seconds and K4 and K5 are constants selected for accurate temperature computation.

6. An electronic thermometer as defined in claim 1, in which is provided means responsive to decreasing values of sampled temperature data over a second selected time interval having a duration less than that of said selected time intervals to supply an error indication to said display.

7. An electronic thermometer as defined in claim 2 or 4, wherein the selected pairs of time intervals are the elapsed time of first and second time periods and the elapsed time of second and third time periods, respectively.

8. An electronic thermometer as defined in claim 3 or 4, wherein the selected one of said time intervals is the elapsed time of a first time period.

9. An electronic thermometer as defined in claim 1, 2 or 4, wherein the high temperature algorithm is

10. An electronic thermometer as defined in claim 1, 3 or 4, wherein the low temperature algorithm is

11. An electronic thermometer as defined in claim 1 or 4, wherein the normal temperature algorithm is