Automatic thermometer calibration system

Abstract

A system for automatically calibrating and classifying measuring instruments such as mercury clinical thermometers, by accurately determining the distance between two reference points established by two known reference parameters. The detection of the reference points is made by scanning a laser beam over the mercury column and detecting the change in the reflection characteristic of the beam at the upper level of the column.

We claim: 
     
       1. A system for automatically calibrating an instrument of the type having a medium extending axially within a relatively narrow column in response to the value of a sensed external parameter, said system comprising means for establishing a first reference parameter at the instrument to thereby cause the medium to rise in the column to a first reference level corresponding to the value of said first reference parameter, first means for scanning a first narrow beam of light over the instrument, first means located in the optical path of said light beam for detecting when said light beam is directed at said first reference level, means spaced from said parameter establishing means for establishing a second reference parameter different from said first reference parameter at the instrument to cause the medium to rise to a second reference level in the column, second means for scanning a second narrow light beam over the instrument, and second means for detecting when said second beam is directed at the medium at said second reference level. 
     
     
       2. The system of claim 1, further comprising means coupled to said first and second detecting means for respectively deactivating said first and second beam scanning means when said beam is directed at said first and second reference levels. 
     
     
       3. The system of claim 2, further comprising first and second indicia forming means respectively coupled to said first and second scanning means and movable along therewith, and means coupled to said first and second detecting means for respectively activating said first and second indicia forming means to thereby respectively establish indications on said instrument at said first and second reference levels. 
     
     
       4. The system of claim 1, further comprising means coupled to said second scanning means for sensing the distance along the column between said first and second reference levels. 
     
     
       5. The system of claim 4 in which said first and second scanning means respectively comprise first and second sources of laser beams, said laser beams respectively defining said first and second narrow light beams, a carrier, first and second reflecting means receiving said laser beams thereon and secured to said carrier, and means for producing relative motion between said carrier and the instrument. 
     
     
       6. The system of claim 5, further comprising means for deriving a first signal corresponding to the distance between said first and second .[.temperature.]. .Iadd.reference .Iaddend.levels, and an instrument release station having a plurality of classifying units, means for transferring the instrument from said second parameter establishing means to said release station, and means responsive to said distance signal and to the position of the instrument for releasing the latter at said release station at a preselected one of said classifying units. 
     
     
       7. The system of claim 6, in which said second scanning means comprises a second carrier carrying said second detecting means, and second reflecting means carried on said second carrier, said distance sensing means comprising means for producing a signal relative to the displacement of said second carrier between said first and second reference levels. 
     
     
       8. The system of claim 7, in which said distance signal producing means comprises encoder means coupled to said second carrier for producing a number of pulses proportional to the distance traveled by said second carrier, and further comprising pulse counting means, means for beginning the counting of said pulses in response to the detection of said second reference level, and means for ending the counting of said pulses in response to the detection of said .[.indication formed on the instrument by said indicia forming means.]. .Iadd.first reference level. .Iaddend. 
     
     
       9. The system of claim 1, further comprising first and second indicia forming means respectively coupled to said first and second scanning means and movable along therewith, and means coupled to said first and second detecting means for respectively activating said first and second indicia forming means to thereby establish indications on said instrument at said first and second reference levels. 
     
     
       10. The system of claim 9, further comprising means coupled to said second scanning means for sensing the distance along the column between said first and second reference levels. 
     
     
       11. The system of claim .[.10.]. .Iadd.4.Iaddend., further comprising means for deriving a first signal corresponding to the distance between said first and second .[.temperature.]. .Iadd.reference .Iaddend.levels, an instrument release station having a plurality of classifying units, means for transferring the instrument from said second parameter establishing means to said release station, and means responsive to said distance signal and to the position of the instrument for releasing the latter at said release station at a preselected one of said classifying units. 
     
     
       12. The system of claim .[.10.]. .Iadd.4.Iaddend., in which said second scanning means comprises a .[.second.]. carrier carrying said second detecting means, and second reflecting means carried on said .[.second.]. carrier, said distance sensing means comprising means for producing a signal relative to the displacement of said .[.second.]. carrier between said first and second reference levels. 
     
     
       13. The system of claim .[.10.]. .Iadd.12.Iaddend., in which said distance signal producing means comprises encoder means coupled to said .[.second.]. carrier for producing a number of pulses proportional to the distance traveled by said .[.second.]. carrier, and further comprising pulse counting means, means for beginning the counting of said pulses in response to the detection of said second reference level, and means for ending the counting of said pulses in response to the detection of said .[.indication formed on the instrument by said indicia forming means.]. .Iadd.first reference level. .Iaddend. .Iadd. 14. In a thermometer calibration process wherein a selected one of a plurality of scales are affixed to a thermometer to match its temperature characteristic, said thermometer having a temperature responsive medium the position of whose end indicates temperature, the method of sorting thermometers into one of a plurality of categories each associated with a particular scale, comprising the steps of heating the thermometer to a first reference temperature, scanning a sensor for locating the end of the temperature responsive medium along the medium and locating the said medium end, heating the thermometer to a second reference temperature different from the first reference temperature to move the medium end to a different position, scanning a sensor for locating the end of the temperature responsive medium along the medium until the changed position of its end is located, converting the difference between the two sensor positions at which the medium end is sensed at the two reference temperatures into an electrical distance signal having a characteristic value which changes in accordance with changes in the sensor position difference, and utilizing the electrical signal's characteristic value to sort the thermometer into that category whose scale substantially corresponds to the temperature characteristic of the thermometer. .Iaddend..Iadd. 15. The method of claim 14 wherein the location of the medium end at one of the reference temperatures is marked on the thermometer..Iaddend. .Iadd. 16. The method of claim 14 wherein the sensor motion is correlated with a pulse generator, the two different sensor positions being converted into a number of pulses whose sum increases as the sensor position difference increases, and counting the number of pulses and utilizing the counted sum to determine into which category the thermometer should be sorted. .Iaddend..Iadd. 17. In a thermometer calibration process wherein a selected one of a plurality of scales are affixed to a thermometer to match its temperature characteristic, said thermometer having a temperature responsive medium the position of whose end indicates temperature, the method of sorting thermometers into one of a plurality of categories each associated with a particular scale, comprising conveying the thermometers in series along a path leading to a sorting station, prior to the sorting station locating for each thermometer two reference positions related to its temperature characteristic, converting the distance between said two reference positions into an electrical distance signal having a characteristic value dependent on said distance, generating an electrical indexing signal representing the indexed position of the thermometer, and processing the distance signal and indexing signal to cause at the sorting station the automatic classification of each thermometer into its proper category. .Iaddend..Iadd. 18. The method of claim 17 wherein the signal processing is such as to cause the automatic release of the thermometer into a selected one of a plurality of receptacles corresonding to the proper category. .Iaddend..Iadd. 19. The method of claim 17 wherein the distance signal is converted to a binary signal. .Iaddend..Iadd. 20. Apparatus for automatically sorting thermometers of the type having a temperature responsive medium the position of whose end indicates temperature into one of a plurality of categories each associated with a scale to be affixed to the thermometer, comprising means for heating the thermometer to at least first and second different reference temperatures whereby the end of the temperature responsive medium is moved between first and second locations corresponding respectively to the first and second reference temperatures, means for sensing the end of the medium, means for scanning the sensor along the medium length, means for converting the difference in the two sensor positions corresponding to the first and second medium end locations into an electrical distance signal having a characteristic value depending upon said difference, and means for processing the distance signal to sort the thermometer into that category associated with that characteristic value of the electrical signal. .Iaddend..Iadd. 21. Apparatus as claimed in claim 20 wherein the signal processing means includes an analog to digital converter. .Iaddend.