D. C. ELECTRONIC APPARATUS FOR IR RADIATION TEMPERATURE MEASUREMENT

• US 3,777,568 A
• Filed: 12/21/1971
• Issued: 12/11/1973
• Est. Priority Date: 12/21/1971
• Status: Expired due to Term

• Current Assignee: Armtec Industries Incorporated Three French Drive Manchester NH
• Original Assignee: Donald M. Szeles, Ojars Risgin
• Inventors: Risgin, Ojars, Szeles, Donald M.
• Primary Examiner(s): Queisser, Richard C.
• Assistant Examiner(s): Shoon, Frederick
• Application Number:
  US05/210,463
• Time in Patent Office: 721 Days
• Field of Search: 73/355EM,355R 235/151.3,193.5
• US Class Current: 374/128
• CPC Class Codes: G01J 5/10 using electric radiation detectors

Abstract

Rapid response, high accuracy, D.C. electronic device for noncontact temperature measurement relying on infrared radiation viewed without use of cyclic interruption of radiation, any type of sequential operation or moving parts and without relying on any type of reference temperature maintenance. A temperature responsive radiation intensity signal (T4(abs) - TR4(abs)) is produced and algebraically combined electronically with an independently sensed reference temperature (TR) raised to the fourth power (TR4(abs)) to produce an output signal (Tabs4) functionally related to object temperature. Extracting the fourth root electronically a signal (Tabs) is produced which is in linear relation to the absolute temperature of the body. Circuit means provide for conversion to Fahrenheit or Centigrade temperature indications for direct reading, recording, or process control.

Claims

1. D.C. electronic temperature-measurement apparatus for noncontact determination of object temperature responsive to infrared radiation from such object, comprising radiation detector means sensitive to infrared radiation from such object to produce an electrical signal responsive to T4 (abs) - TR4 (abs) where T is the temperature in degrees absolute of such object and TR is the reference temperature in degrees absolute at the radiation detector means, thermal sensing means for independently measuring the reference temperature at the radiation detector means to produce an electrical signal responsive to such reference temperature, conversion circuit means for converting the electrical signal produced by the thermal sensing means to an electrical signal representative of the fourth power of such reference temperature in degrees absolute (TR4(abs)), and circuit means for algebraically combining the electrical signals representative of (T4(abs) - TR4(abs)) and TR4(abs) to produce an electrical signal indicative of the temperature of such object, such circuit means including summation circuit means which produce an electrical signal output representative of the fourth power of the temperature of such object in degrees absolute, and further including root extraction circuit means for converting the electrical signal rrpresentative of the fourth power of the temperature of such object in degrees absolute to an electrical signal which is in linear relationship to the temperature of such object.

2. The apparatus of claim 1 in which the electrical signal from the root extraction circuit means is representative of the temperature of such object in degrees absolute, and further including scaling circuit means electrically connected to the root extraction circuit means to produce an electrical output in linear relationship to the temperature of the object in a commonly used temperature scale, such as Fahrenheit and Centigrade temperature scales.

3. The apparatus of claim 2 including digital display means electrically connected to the scaling circuit means for direct numerical display of the temperature of such object.

4. The apparatus of claim 1 in which the radiation detector means comprises thermocouple means including hot junction means for receiving infrared radiation from such object and cold junction means shielded from such infrared radiation so as to generate the electrical signal responsive to T4(abs) - TR4(abs).

5. The apparatus of claim 1 in which the thermal sensing means includes a thermal sensing element and associated circuitry for producing the electrical signal responsive to the reference temperature.

6. The apparatus of claim 5 in which the radiation detector means comprises thermocouple means including hot junction means for receiving infrared radiation from such object and cold junction means shielded from said such infrared radiation, and in which the thermal sensing element is in thermal contact with such cold junction means.

7. The apparatus of claim 6 in which the thermal sensing element comprises thermistor means.

8. The apparatus of claim 7 in which the associated circuitry comprises electrically balanceable network means with tHe thermistor means connected in one balanceable path of balanceable network means, and a voltage source connected across the electrical balanceable network means so as to produce a voltage output responsive to the reference temperature.

9. The apparatus of claim 8 including voltage adjustment means for generating a voltage input for removing that portion of the voltage output due to resistance of the balanceable network means, and summing amplifier means for combining the voltage output of the balanceable network means and the voltage input of the voltage adjustment means to produce a voltage signal in linear relationship to the reference temperature.

10. The apparatus of claim 9 including exponential circuit means for converting the voltage signal in linear relationship to the reference temperature into an electrical signal representative of the fourth power of such reference temperature (TR4(abs)).

11. The apparatus of claim 1 including emissivity calibration means for adjusting the electrical signal indicative of the temperature of the object for infrared radiation characteristics of such object.

12. The D.C. radiation temperature measurement apparatus of claim 1 further including viewing means, in spaced relationship from an object the temperature of which is to be measured, for receiving modulation-free radiation direct from such object.

13. The device of claim 12 in which the viewing means include housing means with window means for directing infrared radiation from such object to the radiation detector means, the housing means including metal support structure for providing thermal contact between the radiation detector means and the thermal sensing means.

14. The device of claim 13 including optic means for focusing infrared radiation on the radiation detector means.

15. The device of claim 14 including focusing gauge means mounted on the housing means for positioning the radiation detector means at optimum focal distance from such object.