DIGITAL READOUT INSTRUMENT EMPLOYING ENABLEMENT CIRCUITS FOR SYSTEM WHEN UNDER READING CONDITIONS

• US 3,785,207 A
• Filed: 06/28/1971
• Issued: 01/15/1974
• Est. Priority Date: 06/28/1971
• Status: Expired due to Term

• Current Assignee: Janusz Brzezinski
• Original Assignee: Janusz Brzezinski
• Inventors: Brzezinski, Janusz
• Primary Examiner(s): Queisser, Richard C.
• Assistant Examiner(s): Shoon, Frederick
• Application Number:
  US05/157,465
• Time in Patent Office: 932 Days
• Field of Search: 73/362AR
• US Class Current: 374/169
• CPC Class Codes: G01K 1/028 arrangements for numerical indication
• CPC Class Codes: G01K 7/42 Circuits effecting compensation of thermal inertia; Circuits for predicting the stationary value of a temperature

Abstract

A digital readout thermometer employing a resistance bridge with a temperature sensitive element such as a thermistor in one leg of the bridge and including a motor driven adjustable resistance or potentiometer for rebalancing the bridge. A servo amplifier, d.c. motor and digital counter provide a reading indicative of the temperature. The circuit includes a differentiator for accelerating the time response of readout. It also includes timer, a comparator, logic circuit and visual indicator for enabling the readout system only when the transducer senses the temperature in the range to be read and the logic circuit is operative to enable the visual indicator when a temperature in the required range has been sensed for a period sufficient for the counter to complete its movement to the correct reading. The thermometer is automatically powered when the probe is removed from its storage tube.

Claims

1. Electronic thermometer comprising:

a probe having temperature sensitive element therein, an enclosure, circuit means within said enclosure for determining temperature of the temperature sensitive element of said probe;

said circuit means including sensing circuit and a servo followup circuit, a temperature display connected to be driven by said servo followup circuit, said enclosure including a recess for storing said probe when not in use;

first switch means responsive to removal of said probe from said recess for applying operating power to said sensing circuit; and

second switch means responsive to operation of said first switch means plus the sensing of a predetermined minimum temperature by said sensing circuit for applying operating power to said servo followup circuit.

2. The combination in accordance with claim 1 including differentiator amplifier means connected between said sensing circuit and said servo circuit for producing an output signal for driving said servo circuit related to the temperature and rate of change of temperature sensed said probe.

3. The combination in accordance with claim 1 wherein said means responsive to said temperatures above the preselected minimum comprises a comparator amplifier including one input terminal connected to a reference voltage source and a second input terminal connected to said sensing circuit to produce a signal whenever the sensing circuit detects a voltage above the reference voltage.

4. The combination in accordance with claim 3 including switch means responsive to the output of said comparator amplifier for enabling the servo circuit.

5. The combination in accordance with claim 4 including a timer responsive to the output of said comparator for limiting the time of enablement of said servo followup circuit to a period sufficient for said servo followup circuit to make the maximum followup adjustment.

6. An electronic thermometer comprising a probe including a temperature sensitive element therein, a sensing circuit for producing an electrical signal related to the temperature sensed by said probe, an indicator, a servo circuit for driving said indicator to a reading indicative of the temperature sensed by said probe, a reference signal source, comparator means for comparing the electrical signal produced by said sensing circuit with said reference signal and for enabling said servo circuit only when said former signal exceeds the reference signal, and timer means for limiting the time of enablement of said servo circuit to a time sufficient to followup to the temperature sensed.

7. The combination in accordance with claim 6 wherein said timer is connected to said comparator to be enabled by the signal from said comparator.

8. An electronic thermometer comprising:

a probe including a temperature sensitive element therein;

a sensing circuit for producing an electrical signal related to the temperature sensed by said probe;

a temperature display;

a servo circuit for driving said temperature display to a reading indicative of the temperature sensed by said probe;

a reference signal source;

comparator means for comparing the electrical signal produced by said sensing circuit with said reference signal and for enabling said servo circuit only when said former signal exceeds the reference signal;

timer means for limiting the time of enablement of said servo circuit to a time sufficient to followup to the temperature sensed; and

indicator means for producing a signal to the user of the beginning of the period of time during which said display registers the probe temperature.

9. The combination in accordance with claim 8 wherein said indicator is a lamp and including means for lighting said lamp following the enabling of said timer.

10. The combination in accordance with claim 9 including logic means for enabling said lamp responsive to an enabling signal from said comparator and after the termination of signal from said timer whereby said lamp is illuminated only after a temperature above a predetermined minimum is sensed and after the necessary time for said servo followup system to move said indicator to a temperature reading equal to the temperature sensed by said probe.

11. The combination in accordance with claim 10 including means for extinguishing said lamp whenever said probe is at a temperature less than the said predetermined minimum.

12. The combination in accordance with claim 11 wherein said lamp extinguishing means comprises said comparator.

13. The combination in accordance with claim 10 including gate means responsive to a signal from said comparator and the end of a timing period of said timer for illuminating said indicator.

14. The combination in accordance with claim 13 wherein said gate responds to the absence of a signal from said comparator to extinguish said indicator.