Electronic thermometer

• US 4,371,271 A
• Filed: 06/04/1980
• Issued: 02/01/1983
• Est. Priority Date: 06/07/1979
• Status: Expired due to Term

• Current Assignee: Bioself International Incorporated Nassau Shirley Street
• Original Assignee: Bioself International Incorporated
• Inventors: Bellet, Jean-Marie
• Primary Examiner(s): YASICH, DANIEL
• Application Number:
  US06/156,447
• Time in Patent Office: 972 Days
• Field of Search: 73/362 AR, 73/362.4, 73/344, 73/342, 331/66
• US Class Current: 374/183
• CPC Class Codes: G01K 1/028 arrangements for numerical indication
• CPC Class Codes: G01K 1/20 Compensating for effects of temperature changes other than those to be measured, e.g. changes in ambient temperature
• CPC Class Codes: G01K 13/20 Clinical contact thermometers for use with humans or animals
• CPC Class Codes: G01K 7/24 in a specially-adapted circuit, e.g. bridge circuit

Abstract

An electronic thermometer comprises a temperature sensitive resistance element to be placed in contact with the area of which the temperature is to be measured. A first relaxation oscillator to which the resistance element belongs, provides a frequency depending on the temperature to be measured. A reference oscillator provides a reference frequency. The first frequency is counted in a counter during a period provided from the reference frequency by a divider. If a temperature or power supply drift affects the reference frequency, the same drift affects in the same direction the counted frequency, so that during the counting the effect of the drift is substantially cancelled. A memory and a comparator record the result of the counting only if it is higher than the preceding result, so that the thermometer operates as a maximum thermometer. The recorded result is provided to a decoder which controls a display device.

Claims

1. An electronic thermometer comprising:

a temperature sensor comprising a remotely located variable resistance element whose resistance value varies as a function of the temperature and adapted to be put in contact with an area the temperature of which is to be measured, a measuring oscillator directly coupled with said variable resistance element and providing a first frequency depending on the value of said resistance, a reference oscillator providing a second, predetermined reference frequency, means for counting the number of cycles of the first frequency, means including divider means for establishing a base equal to a predetermined number of cycles of said reference frequency, means interconnecting said establishing means and said counting means for counting the number of cycles of said first frequency occurring during said predetermined number of cycles of said second frequency, and digital circuit means for providing an indication of the measured temperature in response to the result provided by the counting means, both oscillators being located immediately adjacent one another, so that any ambient temperature or power supply drift fluctuations simultaneously affects the frequencies of the two oscillators in the same fashion, the result of the counting thereby being substantially unaffected by any said drift fluctuations.

2. An electronic thermometer as set forth in claim 1 wherein said divider means has a plurality of stages the final one which reaches a predetermined digital condition when said predetermined number of cycles is attained, and wherein said interconnecting means is connected to said final stage and stops said counting means when said predetermined condition exists in said final stage.

3. An electronic thermometer as set forth in claim 2 and further including memory means interconnected with said counting means for receiving the count therein when said counting means is stopped, display means for indicating the temperature measured, and decoding means interconnecting said memory means and said display means to effect a display according to the contents of said memory means.

4. An electronic thermometer comprising:

a probe body casing ended by a thermoelectric sensor, measuring circuit means coupled with the sensor for providing in the form of a digital data information an indication of the temperature of the sensor, control logic means coupled to the measuring circuit for the control thereof and for receiving the data therefrom, wherein the sensor comprises a variable impedance element of which the value depends on the temperature, wherein the measuring circuit means comprises a first oscillating circuit including said variable impedance element, a second oscillating circuit providing a reference frequency, and means for counting the first frequency, said counting means being controlled by a signal depending on the reference frequency and providing digital data information corresponding to said temperature, and wherein the second oscillating circuit is located closely to and, except for the sensor, is similar to the first oscillating circuit, so that if the frequency of the first oscillating circuit is further influenced by a power supply drift or a thermal drift, the frequency of the second oscillating circuit is then influenced in the same direction by the same drift, the effect of this drift is substantially cancelled, said electronic thermometer further comprising said variable resistance element, control logic means coupled with the counting means for controlling the operation thereof and for receiving the temperature indication therefrom, memory means for receiving and storing said temperature indication, and a self-contained power supply.

5. An electronic thermometer according to claim 4, and further comprising comparator means for periodically comparing said temperature indication with the previously stored temperature indication content of the memory means and, in case the temperature indication exceeds the content, said control logic means causing the input of the temperature indication into the memory, so that the electronic thermometer operates as a maximum thermometer.