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Radiation detector with temperature display

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1. 250 338 1 4 566 808 1 1986 Pompei et al 374 124 4 596 932 6 1986 Buffa et al s 290 374 4 636 091 1 1987 Pompei et al weve 374 124 4 730 940 3 1988 Herber et al e 374 127 4 784 149 11 1988 Berman et al 128 664 OTHER PUBLICATIONS Raynger User s Manual Raytek Inc 1983 pp 1 17 Microscanner E Exergen Corporation Brochure 1985 Primary Examiner Thomas B Will Assistant Examiner Willie Morris Worth Attorney Agent or Firm Hamilton Brook Smith Rey nolds P C 57 ABSTRACT A radiation detector with temperature readout has a multi colored LED display divided into segments of zero degrees to 9 degrees centigrade colored green 10 degrees to 19 degrees centigrade in yellow and 20 degrees to 100 degrees centigrade in red Alternatively two red segments are pro vided for ranges of 20 degrees to 64 degrees centigrade and 65 degrees centigrade and above respectively The radiation detector is automatically zeroed at ambient upon use and provides a readout of temperature rise above ambient throughout a scan of a subject In one design only one LED for each segment of the display is illuminated at a time An audible signal is sounded at an increasing pulse frequency as the display is illuminated from the green segment to the red segment of measured temperature rise above ambient with a constant tone for temperature
2. LED being illuminated at a time a driver for driving the multicolored display means in response to the sensor and a filtering means for substantially filtering out wave lengths of radiation energy generated from sunlight while passing wavelengths of radiation energy gener ated by sources of a flame at about 2000 to about 2500 F 64 A radiation detector as claimed in claim 63 wherein the first red LED indicates temperature from about 20 degrees centigrade to about 65 degrees centigrade the display means further comprising a second red LED for indicating temperature corresponding to sensed radiation from about 65 degrees centigrade and greater 65 A radiation detector adapted for scanning of a target area of electrical equipment comprising a radiation sensor for sensing radiation during scanning of the target area Re 35 554 21 a circuit for establishing a reference signal indicative of a reference amount of radiation detected by the radia tion sensor means for providing an indication of the amount of radiation sensed by the sensor above the reference amount of radiation the means for providing an indi cation comprising sound generator means for produc ing an audible signal having a pulse frequency that increases with increasing radiation detected by the radiation sensor and a filtering means for substantially filtering out wave lengths of radiation energy generated from sunlight while passing wavelengths of
3. indicates that a minimal temperature above ambient is being detected Beeps at a faster pulse frequency indicate that a greater temperature is being detected The user is made aware of a detected dangerous level of temperature rise by a beep signal sounding at a pulse frequency faster than the other two mentioned frequencies Thus the use of the detector is not dependent on a light display which is often difficult to read in sunlight This feature of an audible indication of the detected temperature is discussed and described above Further the audible indication provides a means to alert the user of a temperature rise while scanning a subject Once the user is alerted by an increase in pulse frequency a quantitative analysis of the sensed temperature rise may be obtained by the display Hence the user can scan a subject without specifically knowing where to look for potential heat problems locate the problem area with the audible signal and now knowing where to focus the detector quan tify the detected radiation with the display While this invention has been particularly shown and described with references to preferred embodiments thereof it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims We claim 1 A radiation detector comprising a radiation sensor a display asse
4. radiation energy gener ated by a flame at about 1100 C to about 1370 C 66 A radiation detector adapted for scanning of a target area of electrical equipment comprising a radiation sensor for sensing radiation during scanning of the target area and generating a radiation signal a circuit means for establishing a reference signal being indicative of a reference amount of radiation detected by the radiation sensor and comparing the reference signal to the radiation signal display means responsive to the circuit means for provid ing an indication of the amount of radiation sensed by the sensor above the reference amount of radiation for radiation corresponding to temperatures less then 100 C the display means comprising segments colored green yellow and red respectively wherein only one segment is illuminated at a time and a filtering means for substantially filtering out wave lengths of radiation energy in sunlight from passing to the sensor while passing to the sensor wavelengths of radiation energy generate by a flame at about 1100 C to about 1370 C 67 A radiation detector as claimed in claim 66 wherein the means for providing an indication is a display which comprises a green LED for indicating temperature from about zero degrees centigrade to about 10 degrees centigrade a yellow LED for indicating temperature from about 10 degrees centigrade to about 20 degrees centigrade and a first red LE for indicating temperatu
5. rises above about 20 degrees centigrade In an alternative design a timing circuit allows the detector to self operate for a predetermined length of time The detector sounds a beep tone before automatically shutting itself off A window made of germanium covers the radiation sensor and filters out wavelengths not of interest 77 Claims 4 Drawing Sheets V m BUZZER dis 860 771 U S Patent Jul 8 1997 Sheet 1 of 4 Re 35 554 36 7 4 20 22056 INVESTIGATE IMMEDIATELY POTENTIAL DANGER RED IO TO 20 C REINVESTIGATE CAUTION YELLOW O TO 10 C 24 SCANNING NO ACTION FIG 2 O GREEN 9 8 7 6 5 4 3 2 FIG 3 Re 35 554 Sheet 2 of 4 Jul 8 1997 U S Patent b 9 3 ee Q6 5 E ZH 3 EAE SM 235 O 8 HOSN3S d dv dWv3H lt We ics 84 ge U S Patent Jul 8 1997 Sheet 3 of 4 Re 35 554 o 1 jac mwj ww gt J E BUZZER ae 80 GREEN LED Oo 93 H v REG I TIMER E V TOF EG FIG 5 V REF 5 5 9 U S Patent ryt gt 43 BUZZER Vt 53 a 39 LI 1 p A f Jul 8 1997 Sheet 4 of 4 Re 35 554 O uJ E GREEN LED YELLOW LED RED LEO RED 45 AAY hs a MR 7 5 FIG 6 VEN REG V D SENSOR 37 R
6. sensor and a timing circuit initialized when power is applied to the detector and which maintains power supply to circuits of the detector for a predetermined length of time through control of an internal power switch means and thereafter automatically shuts off the detector by apply ing a control signal to the internal power switch means and a signal to actuate the sound generator means prior to shut off of the detector said reference signal being reset when the detector is turned on subsequent to its automatically shutting off 11 A radiation detector comprising a radiation sensor a display assembly means for providing on a segmented illuminatable display in an indication of the amount of radiation sensed by the radiation sensor above a reference amount of radiation an autozero circuit comprising time controlled means for placing a voltage on a capacitor for establishing a reference signal indicative of a reference amount of radiation detected by the radiation sensor and sensor from a reference target means for summing the reference signal being summed with a radiation signal indicative of the amount of sensed radiation subsequently detected by the radiation sensor to provide a display signal the display assembly means being responsive to the display signal and thereby providing on the display an indication of the amount of a radiation sensed above the reference amount of radiation and timing means for controlling the
7. temperature within a range of temperatures higher above the tem perature corresponding to the reference amount of radiation than the range of the green LED and a first red LED for indicating the detection of an amount of radiation which has a corresponding temperature within a range of temperatures higher above the tem perature corresponding to the reference amount of radiation than the range of the yellow LED and wherein only one LED is illuminated at a time 19 A radiation detector as claimed in claim 18 further comprising a second red LED for indicating the detection of an amount of radiation which has a corresponding tempera ture within a range of temperatures higher above the tem perature corresponding to the reference amount of radiation than the range of the first red LED and wherein the first red LED indicates a range of temperatures of about 20 degrees to 64 degrees centrigrade above the temperature correspond ing to the reference amount of radiation and the second red LED indicates a range of temperatures of about 65 degrees centigrade and greater above the temperature corresponding to the reference amount of radiation 20 A radiation detector as claimed in claim 11 further comprising a window the window covering said sensor to filter out short wavelengths on the order of less than about 1 5 microns while allowing longer wavelengths of about 1 5 to 3 microns and greater to be detected by said sensor 21 A radiation detecto
8. temperature and greater and wherein only one LED is illuminated at a time 49 A radiation detector as claimed in claim 48 wherein the first red LED indicates temperature from about 20 degrees centigrade to about 65 degrees centigrade above 15 35 a 45 65 Re 35 554 19 ambient temperature the display assembly further compris ing a second red LED for indicating temperature from about 65 degrees centigrade above ambient temperature and greater 50 A radiation detector as claimed in claim 46 further comprising filtering means for substantially filtering out wavelengths of energy generated from sunlight while pass ing wavelengths generated by a flame at about 1100 C to about 1370 C 51 A radiation detector as claimed in claim 50 wherein said filtering means is a long wave pass filter which starts passing light at wavelengths in the range of about 1 5 microns to 3 0 microns 52 A radiation detector comprises a radiation sensor providing a radiation signal indicative of sensed radiation an autozero circuit means which establishes a reference signal means for combining the reference signal with said radia tion signal to provide a temperature difference signal sound generator means for producing an audible signal responsive to the temperature difference signal and a display assembly means responsive to the temperature difference signal and having a multicolor display for providing a visual indication of t
9. the detected ambient temperature than the range of the yellow LED and wherein only one LED is illuminated at a time 25 A radiation detector as claimed in claim 24 further comprising a second red LED for indicating the detection of an amount of radiation which has a corresponding tempera ture within a range of temperatures higher above the detected ambient temperature than the range of the first red LED 26 A radiation detector comprising a radiation sensor a display assembly means associated with the sensor for providing on a display a temperature indication rela 10 15 20 25 35 45 55 65 16 tive to an ambient temperature of the amount of radiation sensed by the radiation sensor the display being accurate for radiation amounts corresponding to temperatures above the ambient temperature about 100 C and lower means for filtering out short wavelengths on the order of less than about 1 5 microns while allowing longer wavelengths in a range about 1 5 to 3 microns and greater generated by sources of interest to be sensed by said sensor and a housing for holding the sensor display assembly means display and means for filtering the housing being of dimensions enabling hand held usage of the detector 27 A radiation detector as claimed in claim 26 wherein said means for filtering is a window comprising germanium the window covering said sensor 28 A radiation sensor as claimed in claim 26 wherein
10. United States Patent Pompei et al 11 E 45 Reissued Date of Patent USOORE35554E Patent Number Re 35 554 Jul 8 1997 54 RADIATION DETECTOR WITH TEMPERATURE DISPLAY 75 Inventors Francesco Pompei Boston Michael W Burke Natick both of Mass 73 Assignee Exergen Corporation Watertown 21 Appl No 222 324 22 Filed Apr 4 1994 Related U S Patent Documents Reissue of 64 Patent No 4 874 253 Issued Oct 17 1989 Appl No 32 067 Filed Mar 27 1987 U S Applications 63 Continuation of Ser No 778 046 Oct 16 1991 abandoned 51 Int CL a G01J 5 26 52 U S e 374 121 374 128 58 Field of Search 374 121 124 374 128 129 130 133 340 586 600 56 References Cited U S PATENT DOCUMENTS 3 282 106 11 1966 Barnes 73 355 3 444 739 5 1969 Treharne 374 124 374 128 3 777 568 12 1973 Risgin et al 250 343 4013260 3 1977 McClatchie et al 4 081 678 3 1978 Macall 250 330 4 317 998 3 1982 Dore eee 250 357 4 321 594 3 1982 Galvin et al 340 567 4 343 182 8 1982 Pompei e 374 31 4 372 600 2 1983 Berman et al 374 29 374 133 374 128 4 420265 12 1983 Everest et al s 4 456 390 6 1984 Junkert et al 4 481 417 11 1984 Inglee
11. a radiation signal indicative of sensed radiation a display means for providing a quantitative indication of a sensed temperature difference circuit means responsive to the radiation sensor for zeroing the radiation detector by establishing a refer ence signal indicative of an ambient temperature and for driving the display means to provide the quantita tive indication of the sensed temperature difference between a temperature corresponding to an amount of sensed radiation during scanning of the target area which is higher than the ambient temperature and the reference signal indicative of the ambient temperature sound generator means responsive to the radiation sensor and circuit means for generating an audible signal indicative of sensed temperature difference between a temperature corresponding to an amount of sensed radiation during scanning of the target area and the reference signal indicative of an ambient tempera ture 47 A radiation detector as claimed in claim 46 wherein 55 said display means comprises segments of different colors for providing a visual indication of sensed radiation relative to ambient temperature 48 A radiation detector as claimed in claim 46 wherein the display means comprises a green LED for indicating 60 temperature from about zero degrees centigrade to about 10 degrees centigrade above ambient temperature and a first red LED for indicating temperature from about 20 degrees centigrade above ambient
12. adiation received through one end of the housing a display assembly means having a display on the housing the assembly means being responsive to the sensed radiation and driving the display to provide a temperature indication relative to the amount of radia tion sensed by the radiation sensor and filtering means for substantially filtering out wavelengths of energy generated from sunlight while passing wave lengths generated by sources of interest and for sub stantially allowing wavelengths of energy from a flame about 1100 to about 1370 C to be sensed by the sensor such that a relative temperature indication thereof is provided on the display the display only providing accurate temperature indications up to tem peratures substantially less than that of the flame 33 A radiation detector comprising a radiation sensor means for establishing a reference signal indicative of a reference temperature when the detector is turned on Re 35 554 17 a display assembly means responsive to said reference signal and signals of the sensor indicative of sensed radiation for providing on a display an indication of the temperature of a subject above said reference tempera ture a timing circuit means which maintains the detector in operation for a predetermined length of time and there after automatically shuts off the detector and provides an actuating signal to a means for producing an audible signal said reference temperature be
13. ar graph display which responds to a radiation sensor and provides a temperature signal of a subject above a reference temperature The bar graph display is arranged into three segments of about zero degrees centigrade to 9 degrees centigrade about 10 degrees to 19 degrees centigrade and about 20 degrees centigrade and greater Each segment is of a different color It is preferred that the segments are colored green yellow and red respectively indicating the recommended guidelines of insurance and utility companies for the indicated tempera ture rise above ambient temperature The green segment indicates an acceptable temperature rise The yellow seg ment indicates a potential problem and that reinvestigation is needed The red segment indicates an immediate problem The segments are illuminated from zero degrees to the indicated temperature to give a full bar indication of the amount of radiation sensed by the radiation sensor The red segment flashes on and off when a temperature rise above 100 degrees centigrade is detected The display includes elements which are driven in a piecewise linear fashion The elements are grouped together and each group is associated with a display driver The display drivers respond to a display input indicative of the amount of radiation sensed by the radiation sensor and incrementally select display elements Each driver responds to a single incremental change in the display input for different selections of
14. ations of electrical equipment 41 A radiation detector as claimed in claim 32 wherein 5 the filtering means comprises a lens 42 A method of sensing radiation the steps comprising zeroing a radiation detector by detecting with the detector radiation indicative of an ambient temperature scanning a target area with the radiation detector the 10 detector having an audible signal a frequency of which is indicative of sensed temperature differences between a temperature corresponding to an amount of detected radiation during the scanning and the previously detected ambient temperature locating a subject within the target area by the frequency of the audible signal and providing a quantitative indication of temperature of the located subject using a display of the radiation detec tor 43 A method as claimed in claim 42 further comprising the step of filtering out short wavelengths of less than about 1 5 microns while allowing longer wavelengths of interest to be sensed by the radiation detector 44 A method as claimed in claim 42 wherein the step of providing a quantitative indication includes providing a display of the temperature with colors indicating different temperatures 45 A method as claimed in claim 42 wherein the scanning step includes scanning a target area of electrical equipment with the radiation detector 46 A radiation detector adapted for scanning a target area comprising a radiation sensor providing
15. ature signal is established by placing a voltage on a capacitor 8 A radiation detector as claimed in claim 1 further comprising a window the window covering said sensor to filter out short wavelengths on the order of less than about 1 5 microns while allowing longer wavelengths of about 1 5 to 3 microns and greater to be detected by said sensor 9 A radiation detector as claimed in claim 8 wherein the 6 Window comprises germanium 65 10 A radiation detector comprising a radiation sensor providing a radiation signal indicative of sensed radiation an autozero circuit which establishes a reference signal which is summed by summing means with the radiation signal from the radiation sensor to provide a display signal Re 35 554 13 a display assembly responsive to the display signal and having a multicolor display for providing a visual indication of the amount of radiation sensed by the radiation sensor the display arranged in segments of different colors a sound generator means for generating an audible signal with differing pulse frequencies each pulse frequency corresponding to an amount of radiation indicated by the display such that the pulse frequency increases for increasing amount of radiation indicated on the display means for filtering out short wavelengths on the order of less than about 1 5 microns while allowing longer wavelengths above about 1 5 microns generated by sources of interest to be sensed by the
16. avelengths which can be readily distinguished with a wide range of filters A further consideration however is that a user is likely to want to assure proper operation of a device by viewing a known hot source such as a match or light bulb Such sources produce radiation of wavelengths much closer to those of sunlight and require much more specific filtering to allow for their detection to the exclusion of sunlight To ensure accurate infrared detection out of doors a window 86 made of germanium covers the radiation sensor within the radiation sensor assembly 16 of FIG 1 A lens comprising germanium is also suitable The germanium window 86 or lens acts as a filter allowing only energy of certain wavelengths to be detected by the radiation sensor The germanium glass filters out short wavelengths of less than about 1 7 microns from detection by the radiation sensor 9096 of the wavelengths in sunlight arc less than 1 5 microns Although the wavelengths of energy from hot Re 35 554 11 electrical connectors are significantly greater than 1 5 microns it is desirable to detect shorter wavelengths result ing from the flame of a match to assure proper operation of the unit The flames of interest are on the order of about 20005 F to 2500 F and produce wavelengths of about 1 7 to 3 microns with a peak at about 2 microns Thus the germanium glass filters out about 90 of the sunlight energy and only rejects about 10 of the energy of a flam
17. ay 78 approaches the zero level of the bar graph This is accomplished by tapping the input to the LED at the 10 degree level of the bar graph so that when the display 78 reaches this level a D flip flop opens one switch reducing the rate at which charge is bled off from the reference capacitor Likewise input to the LED at the zero degree level of the bar graph is tapped to provide an indication of the display 78 approaching the zero degree level A second D flip flop is then triggered and a second switch stops the bleeding of charge from the reference capacitor The amount of charge of the reduced reference signal is inversely related to the radiation sensed from the ambient surface and is reproduced at the output of buffer 47 to be added to each signal from the radiation sensor 83 throughout the scan The display 78 is thus autozeroed and provides readings of the temperature rise above ambient Shown in FIG 5 is another embodiment of the invention with a different autozero circuit than in the embodiment of 10 15 35 45 55 65 8 FIG 4 and which is designed for the minimization of production costs The autozero circuit of the embodiment in FIG 5 may also be used in the embodiment of FIG 4 In FIG 5 an autozero reference signal is established by the user closing switch 15 which is the power switch connecting the 9 v battery 9 to the V and other lines of the circuit The radiation sensor 13 detects the radiation of the obj
18. dentifying electrical equipment oper ating temperature the method comprising determining an ambient level of radiation with a radiation sensor scanning a target area comprising electrical equipment with the radiation sensor filtering radiation from the target area to the radiation sensor by attenuating short wavelengths of radiation of less than about 1 5 microns and substantially passing wavelengths between 1 7 and 3 microns and greater including wavelengths emitted by electrical equipment at less than 100 C detecting the filtered radiation with the radiation sensor 10 24 displaying a visible indication of operating temperature corresponding to an amount of the detected filtered radiation above a level corresponding to the ambient level of radiation 78 A method as claimed in claim 77 wherein displaying the visible indication comprises driving a multicolor bar graph providing the visible indication in response to the detected radiation 79 A method as claim in claim 77 further comprising identifying electrical equipment exhibiting an aberrant tem perature in response to the detected radiation exceeding the level corresponding the ambient level of radiation by a predetermined amount
19. display elements but different drivers respond to different incremental changes for different selec tions of display elements Thus the display drivers provide a piecewise linear approximation of temperature which is a nonlinear function of the sensed heat flux The display provides a wide range of temperatures by each group of elements being divided into different tem perature increments Specifically the 20 degrees centigrade and above segment of the bar graph display is divided into larger temperature increments than the 0 degrees to 9 15 35 40 45 55 65 2 degrees centigrade and the 10 degrees to 19 degrees centi grade segments The detector establishes the reference temperature by an autozero circuit The autozero circuit initially establishes a high reference signal which results in a display signal above the zero level of the bar graph The high reference signal is reduced until the display signal reaches the zero level of the bar graph at which point the reference signal is held During a subsequent scan of the target the autozero circuit sums the reference signal with a radiation signal indicative of the amount of sensed radiation This sum provides the display signal DISCLOSURE OF THE INVENTION An object of the present invention is to provide a device that is easily and quickly used by a relatively inexperienced technician to determine the heat losses and temperature rise above a reference temperature of e
20. duces a negative reference signal which is applied through a buffer 47 to the summing node 66 where it is summed with a subsequent negative radiation signal from IR sensor 83 This summed voltage is amplified in amplifier 67 The output voltage from amplifier 67 triggers the display 78 to provide an indication of the sensed radiation The output voltage from amplifier 67 also controls the voltage to frequency device 92 which controls the pulse frequency of buzzer 70 The output voltage is offset at comparator 90 to produce the lowest duty cycle of the voltage of frequency device 92 at ambient The output voltage form amplifier 67 causes the voltage to frequency device 92 to pulse the clock of the D flip flop 32 Each time the clock is pulsed the D flip flop 32 produces output Q directly from input D Output Q leads into the D input of D flip flop 32 so that after each pulsing of the clock a change in Q will result in a subsequent change in the D input so that on the next clock pulse a change in Q will occur Thus D flip flop 32 ensures a 50 duty cycle of the buzzer 70 and the frequency of the D flip flop 32 is generated by the voltage to frequency device 92 As the temperature sensed by the sensor 83 increases so does the output voltage from amplifier 67 In turn the increased output voltage from amplifier 67 causes the volt age to frequency device 92 to produce a more frequent clocking signal to D flip flop 32 which causes an increase in the
21. e The germanium window 86 serves a further purpose of preventing sunlight from burning out the sensor Because the wavelengths of sunlight and other visible light are short less than about 1 5 microns it takes a very short time of exposure to such light to over expose and thus burn out the sensor Hence by the germanium window 86 filtering out the short wavelengths of sunlight and other visible light the sensor is safeguarded against over exposure and subsequent burn out In the past coated germanium windows were used as long wave pass filters Coated germanium starts passing wave lengths at about 7 to 8 microns Thus a coated germanium window would not allow detection of the shorter wave lengths of a flame test Consequently applicant uses uncoated germanium glass for window 86 In contrast ordinary glass filters out wavelengths less greater than about 3 microns Ordinary glass rejects about 30 40 of the wavelengths of a flame Other glass filters however are suitable and may be used in place of window 86 In general it is best to have a long wave pass filter and sensor which provides a threshold between about 1 5 and 3 0 microns Another problem with the outdoor use of past detectors is the glare from sunlight causing difficulties in reading the detector display In the present invention this problem is overcome by the audio indication of the detected tempera ture rise above ambient A continuous slow pulsing beep tone
22. e 35 554 1 RADIATION DETECTOR WITH TEMPERATURE DISPLAY Matter enclosed in heavy brackets appears in the original patent but forms no part of this reissue specifi cation matter printed in italics indicates the additions made by reissue This application is a continuation of co pending appli cation Ser No 07 778 046 filed Oct 16 1991 now abandoned which is a Reissue of Ser No 07 032 067 filed on Mar 27 1987 U S Pat No 4 874 253 BACKGROUND Over time the repeated normal use of electrical equip ment causes electrical connections to become loose and weak The increased electrical resistance of such connec tions can result in heating which presents a fire hazard Insurance and utility companies have recommended guide lines that establish temperatures which indicate that correc tive action should be taken In the past inspection of electrical equipment for such faults was unsafe costly and or inaccurate Infrared inspection has been used as a fast easy and very effective way of detecting electrical problems by the heat generated Infrared inspection is safe as no contact is made with the electrical equipment It is cost effective and accurate as the equipment is not shut down Infrared inspection can also be used to detect fire from sources other than electrical equipment One such infrared detector is the Microscanner E manu factured by EXERGEN Corp of Natick MA That detector comprises a multicolor full b
23. e apparent from the following more particular description of preferred embodiments of the invention as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views The drawings are not nec essarily to scale emphasis instead being placed upon illus trating the principles of the invention FIG 1 is a perspective view of a heat detector embodying this invention and having a multicolor bar graph display at an end of a housing opposite to a radiation sensor FIG 2 is a schematic illustration of use of the detector of FIG 1 to scan a radiation source 10 15 25 35 45 55 65 4 FIG 3 is an enlarged illustration of the scale of the multicolor bar graph of FIG 1 with the guidelines recom mended by insurance and utility companies FIG 4 is an electrical schematic diagram of the electrical circuit used in an embodiment of the invention having a timing circuit FIG 5 is an electrical schematic diagram of the low cost electrical circuit of another embodiment of the invention FIG 6 is an electrical schematic diagram of the electrical circuit used in an embodiment of the invention having a four LED display DESCRIPTION OF PREFERRED EMBODIMENTS A radiation detector 12 comprises a boxlike housing 14 This housing has an approximate dimension of 344 x5 x54 The flat handheld housing can be easily carried in a pocket A radiation sensor assembly 16
24. e more stage responding to 17 mV increments Beyond the 0 336 mV the driver increments the display at 230 mV increments Those increments account for the third piece of the piece wise linear approximately of temperature with ten degree increments As previously stated at the beginning of each scan illustrated in FIG 2 the display is automatically zeroed at the ambient temperature of the neutral surface at which the device is first pointed using an autozero circuit as com monly known in the art Referring to FIG 4 power is applied from the battery 82 through switch K1 to the entire circuit The transition to a high potential results in a positive pulse at an opposite side of a capacitor in autozero circuit 48 which triggers a comparator A negative pulse results at the output of the comparator to draw current through a diode and a resistor and place a negative charge on a reference capaci tor That negative potential is applied through a buffer 47 to the summing node 66 where it is summed with the negative radiation signal The charge initially placed on the reference capacitor establishes a high negative reference signal which results in the display 78 being set well above the zero degree centigrade level of the bar graph The high reference signal is then reduced by bleeding the charge from the reference capacitor until the display 78 reachbes the zero level of the bar graph The reference signal is reduced at a decreasing rate as the displ
25. ect at which the device is initially pointing Provided that the initial object is at a temperature above ambient the sensed radiation produces a negative voltage which is applied through the dual operational amplifiers 21 and 23 to produce a gain in voltage Switch 25 is closed by timer 11 when the device is turned on Switch 25 allows the negative voltage to charge the capacitor 19 to a level indicative of the temperature of the object toward which the device initially points Timer 11 holds switch 25 closed about 500 msec which is long enough for the capacitor 19 to be charged by the initial negative voltage from the radiation sensor 13 At the end of the 500 msec the timer opens switch 25 to discontinue the charging of the capacitor 19 The initial high voltage output of the timer 11 also holds the buzzer 80 off and disables the display decoder 75 while the capacitor 19 is being charged After the allotted time the timer output voltage drops to reset the buzzer 80 and enable the 2 to 4 decoder 75 The enablement of the decoder causes the green LED to light thus signifying that the unit has been autozeroed The negative charge held by the capacitor 19 is applied to a buffer 27 The negative voltage output of buffer 27 is the autozero reference signal which is later input to differential amplifier 29 with subsequent radiation signals from ampli fier 23 indicative of temperatures sensed by sensor 13 The output voltage from amplifier 29 is a
26. etector by opening the internal switch 2 A radiation detector as claimed in claim 1 wherein said display is arranged in segments of different colors 3 A radiation detector as claimed in claim 2 wherein the colors of said segments are green yellow and red respec tively 4 A radiation detector as claimed in claim 1 wherein said display has segments arranged to indicate temperature from about zero degrees centigrade to about 9 degrees centigrade about 10 degrees to about 19 degrees centigrade and about 20 degrees centigrade and greater respectively 5 A radiation detector as claimed in claim 1 wherein the means for producing an audible signal includes means producing an audible signal having a pulse frequency that increases in correspondence with each temperature increase detected by the sensor and indicated in the display the means being associated with the signals indicative of detected radiation 6 A radiation detector as claimed in claim 1 further comprising an autozero circuit which establishes the refer ence temperature signal which is summed with said signal indicative of detected radiation to produce a display signal the autozero circuit comprising means for establishing the reference temperature signal indicative of ambient tempera ture and means for holding the reference signal the display assembly means being responsive to the display signal 7 A radiation detector as claimed in claim 6 wherein said reference temper
27. gher change in sensed radiation the voltage across resistors 54 and 3 is matched and comparator 63 is enabled Comparator 63 places a high input to decoder 45 which in turn selects to illuminate just the second red LED The output voltage from amplifier 56 also controls the voltage to frequency device 60 which pulses the clock of D flip flop 68 sounding buzzer 43 in a manner similar to that described in the circuit of FIG 5 The output voltage is offset by the reference voltage from reference voltage generator 85 at comparator 52 so that the voltage to frequency device 60 is at its lowest frequency at ambient and at its highest frequency when near the 20 degree centigrade sensed Change in radiation threshhold Once this threshhold is crossed the buzzer 43 will sound continuously The buzzer sounds with increasing pulse frequency corresponding to the green yellow and two red LED s respectively in the same manner as the buzzer 80 in the embodiment of FIG 5 The buzzer 43 can be disabled by the user pressing switch 22 for applications where the audible signal is not wanted Wavelengths are shorter from hotter sources of radiation The device must detect wavelengths which are short relative to those from bodies at ambient temperature On the other hand the radiation from the very hot sun is of very short wavelengths and sunlight should not be detected Relative to the radiation from the sun overheated electrical connectors have relatively long w
28. gy than the autozero target amplifier 56 has a negative output 10 15 25 35 45 55 10 The output is about 7 39 mv btu hr sq ft sensed above or below the autozero target That is the output voltage from amplifier 56 is a voltage indicative of the difference between the reference temperature and the temperature being observed The voltage drives comparators 63 72 and 76 to produce inputs to a 3 to 8 decoder 45 The second inputs to the comparators are taken from a voltage divider of resistors 54 3 7 and 5 which divides the 2 53 V reference voltage from reference voltage generator 85 into voltages corre sponding to the sensed change in radiation with the change in temperatures of the display With a low sensed change in radiation the output voltage from amplifier 56 is less than that across resistor 5 and none of the three comparators are enabled The decoder 45 in turn illuminates only the green LED With a somewhat higher change in sensed radiation the output voltage surpasses that across resistor 5 and comparator 76 is enabled Comparator 76 then places a high input to decoder 45 which causes the decoder to illuminate the yellow LED and dim the green LED With a higher change in sensed radiation the voltage across resistors 3 and 7 is matched and comparator 72 is enabled Comparator 72 in turn places a high input to decoder 45 which causes the first red LED to be illuminated and the yellow LED to be dimmed With yet a hi
29. he temperature differ ence signal wherein the display comprises a green LED for indicating temperature from about zero degrees centigrade to about 10 degrees centigrade a yellow LED for indicating temperature from about 20 10 15 25 degrees centigrade to about 20 degrees centigrade and 30 a first red LED for indicating temperature from about 20 degrees centigrade and greater and wherein only one LED is illuminated at a time 53 A radiation detector as claimed in claim 52 wherein the first red LED indicates temperature from about 20 degrees centigrade to about 65 degrees centigrade the display assembly further comprising a second red LED for indicating temperature from about 65 degrees centigrade and greater 54 A radiation detector as claimed in claim 52 wherein said detector is adapted to sense radiation from electrical equipment 55 A radiation detector as claimed in claim 52 wherein the sound generator means produces an audible signal having a pulse frequency that increases in correspondence with increasing temperature detected by the sensor and indicated by the display 56 A radiation detector as claimed in claim 52 further comprising means for housing the radiation detector said housing means having an opening the radiation sensor being positioned in the housing means to sense radiation passing through the opening the housing being adapted to be hand held during use of the detector 57 A radiation detector as cla
30. imed in claim 52 further comprising filtering means for substantially filtering out wavelengths of energy generated from sunlight while pass ing wavelengths generated by a flame at about 1100 C to about 1370 C 58 A radiation detector as claimed in claim 57 wherein said filtering means is a long wave pass filter which starts passing light at wavelengths in the range of about 1 5 microns to 3 0 microns 59 A radiation detector as claimed in claim 57 compris ing a lens through which radiation is received by the radiation sensor 60 A radiation detector adapted for scanning of a target area comprising 45 55 60 65 20 a housing adapted to be hand held during the use of a detector a radiation sensor positioned in the housing for sensing radiation received through one end of the housing and generating a radiation signal indicating levels of the radiation a circuit for generating a reference signal from the radiation signal indicative of ambient radiation levels a multicolor display means for providing a visual quan titative indication of a difference signal in green yellow and red segments of an LED display a filtering means for substantially filtering out wave lengths of radiation energy generated from sunlight while passing wavelengths of radiation energy gener ated by sources of a flame at about 1100 to about 1370 C sound generator means for producing an audible signal having a pulse frequency that increa
31. ing being of dimensions enabling hand held usage of the detector 72 A radiation detector as claimed in claim 71 wherein the filter attenuates wavelengths of reflected sunlight and other visible light 73 A radiation detecting device comprising a radiation sensor generating a detected radiation signal in response to received radiation a filter in front of the radiation sensor attenuating short wavelengths of radiation contained in sunlight and substantially passing wavelengths of radiation associ ated with a flame about 2000 to about 2500 F and wavelengths of radiation associated with temperatures substantially less than the flame a bar graph display indicating temperatures substantially less than the flame and a circuit generating a comparison of the detected radia tion signal and an ambient radiation signal represent ing an ambient level of radiation and driving the display in response to the comparison 74 A radiation detecting device as claimed in claim 73 wherein the bar graph display comprises a multicolor bar graph for providing a visible indication of a temperature above an ambient temperature of a target at which the radiation sensor is directed 75 A radiation detecting device as claimed in claim 73 wherein the filter blocks wavelengths of about 1 5 microns and less Re 35 554 23 76 A radiation detecting device as claimed in claim 73 wherein the filter comprises a germanium lens 77 A method for i
32. ing reestablished when the detector is turned on subsequent to its auto matically shutting off said means for producing an audible signal having a pulse frequency that increases in correspondence with each temperature increase detected by the sensor and indi cated in the display said audible signal further sound ing just once before the automatic turning off of the detector in response to a signal from said timing circuit means 34 A radiation detector comprising a radiation sensor an autozero circuit means for establishing a reference signal indicative of a reference temperature when the detector is turned on a display assembly means responsive to signals indicative of radiation levels detected by the sensor for providing on a display an indication of the temperature of a subject above said reference temperature a timing circuit means which maintains the detector in operation for a predetermined length of time and there after automatically shuts off the detector said reference signal being reestablished when the detector is turned on subsequent to its automatically shutting off and said autozero circuit means establishes said reference signal and sums it with a radiation signal indicative of sensed radiation to produce a display signal the autoz ero circuit means further comprising means for holding the reference signal said reference signal being rees tablished by placing a voltage on a capacitor 35 A radiation detecto
33. inputs to the two compara tors are taken from voltage dividers which divide the refer ence voltage from the reference voltage generator With low temperatures the summed signals are less than the voltage needed to enable either comparator so only the green LED is illuminated With higher temperatures the sum enables one comparator which causes the decoder to illuminate just the yellow LED With even higher temperatures the sum enables both comparators causing the decoder to illuminate the red LED The buzzer sounds in reference to the three LED s A slow continuous pulse frequency sounds for the temperatures sensed in the range of temperatures illuminating the green LED The pulse frequency increases for increasing tempera tures within the green LED range up through the red LED temperature range The highest pulse frequencies sound when sensed temperatures are in the temperature range for which the red LED is illuminated with a constant tone sounding for sensed temperatures above a threshold tem perature In another design of the invention the display is arranged into four segments colored green yellow red and a second red respectively The green segment indicates a sensed rise in temperature of less than about 10 degrees centigrade above ambient The yellow segment indicates a temperature rise of more than about 10 degrees centigrade and less than about 20 degrees centigrade The first red segment indicates a temperature rise between abo
34. is positioned at one end of the housing 14 An LED bar graph display 18 is located at the end of the housing 14 opposite to the sensor assembly 16 This par ticular bar graph includes the scale from 0 degree centigrade to 100 degree centigrade As shown in FIG 3 a 0 degree to 20 degree part of the scale is divided into 1 degree incre ments The 20 degree to 100 degree part of the scale is divided into 10 degree increments The 0 degree to 9 degree segment is colored green indicating no need for corrective action according to the guidelines recommended by insur ance and utility companies The 10 degree to 19 degree segment is colored yellow indicating a need to reinvestigate The 20 degree to 100 degree segment is colored red indi cating a need to investigate immediately These inspection guidelines are detailed on one side of the housing 14 The region 20 in FIG 1 is illuminated from 0 degree centigrade to the indicated temperature providing a full bar indication of radiation detected by the sensor assembly 16 relative to an ambient reference established by an autozero circuit to be described The segment colored red flashes on and off for detected temperature rise above 100 degrees centigrade In another embodiment of the invention the bar graph does not include a numerical scale Instead the bar graph includes the three segments colored green yellow and red respectively indicating the corrective action recommended by the insurance and u
35. l during the time in which reference signal voltage is placed on the capacitor and enables the audible signal producing means to sound the audible signal there after when the display in illuminated 15 A radiation detector as claimed in claim 14 wherein the means for producing an audible signal includes a buzzer which is disabled and enabled by a switch controlled by the user 16 A radiation detector as claimed in claim 11 further comprising means for producing an audible signal having a pulse frequency that increases for each increase in amount of sensed radiation indicated by the display the and means for producing disabling production of the audible signal being disabled by said timing means during the time in which the reference signal is established and enabled thereafter for enabling production of the audible signal after the reference signal is established 17 A radiation detector as claimed in claim 16 wherein the means for producing an audible signal includes a buzzer which is enabled and disabled by a switch controlled by a user 18 A radiation detector as claimed in claim 11 wherein the display includes a green LED for indicating the detection of an amount of radiation which has a corresponding temperature within a range of temperatures slightly above the temperature corresponding to the reference amount of radiation a yellow LED for indicating the detection of an amount of radiation which has a corresponding
36. lectively actuating said display assembly and a means for producing an audible signal said audible signal corresponds corresponding to each LED such that the pulse frequency of the audible signal increases for each temperature increase of sensed radia tion indicated within each LED and continues to increase for each temperature increase of sensed radia tion indicated from one LED to the next and means for filtering out short wavelengths on the order of less than about 1 5 microns while allowing longer wavelengths generated by sources of interest to be sensed by the sensor 23 A radiation detector as claimed in claim 22 wherein said means for producing an audible signal limits the pulse frequency such that the audible signal is at a constant tone for sensed temperature increase above 20 degrees centi grade 24 A radiation detector as claimed in claim 22 wherein said display includes a green LED for indicating the detection of an amount of radiation which has a corresponding temperature within a range of temperatures slightly above the detected ambient temperature a yellow LED for indicating the detection of an amount of radiation which has a corresponding temperature within a range of temperatures higher above the detected ambient temperature than the range of the green LED and a first red LED for indicating the detection of an amount of radiation which has a corresponding temperature within a range of temperatures higher above
37. lectrical equipment and other surfaces A further object of the invention is to provide such a device which is relatively inexpensive portable and accurate outdoors as well as indoors In one design of the invention the device with an autozero circuit is held on for about 30 seconds by a timing circuit The timing circuit automatically turns the device off at the end of about 30 seconds and sounds a beep tone to signify its turning off The timing circuit and the autozero circuit are reset each time the user turns on the power of the detector The detector includes a multicolor display which responds to the sensor and provides an indication of the temperature of a subject above the reference temperature The display shows three colored segments green yellow and red signi fying no problem caution and danger readings respectively with or without numerical references The green segment corresponds to a temperature rise above reference of about 0 degrees centigrade to 9 degrees centigrade The yellow segment corresponds to a temperature rise of about 10 degrees to 19 degrees centigrade and the red segment corresponds to a temperature rise of about 20 degrees centigrade and greater In another design of the invention as the segments are illuminated a pulsed audible signal sounds with increasing pulse frequency from the no problem segment to the danger reading segment In accordance with another aspect of the invention the a
38. lip flop 17 which causes an increase in the pulsing frequency of buzzer 80 Also as the temperature sensed by the sensor 13 increases the output voltage from amplifier 29 increases to produce an increase in pulse frequency of the buzzer 80 The increasing pulse frequencies of the buzzer 80 correspond to the green yellow and red LED s respectively A slow continuous pulse frequency sounds for the temperatures sensed in the range of temperatures illuminating the green LED The pulse frequency increases for increasing tempera tures within the green LED range and continues to increase through the yellow and red LED temperature range The fastest pulse frequencies sound when sensed temperatures are in the temperature range for which the red LED is illuminated the voltage to frequency device 10 reaching a limit and causing the buzzer 80 to emit a constant tone for sensed temperatures above about 20 degrees By pressing switch 81 the user can disable the buzzer 80 for situations where the audible signal is not wanted In an alternative embodiment a four LED display is driven by three comparators and a 3 to 8 decoder as shown in FIG 6 The rest of the electrical circuit is the same as in the embodiment of FIG 5 The four LED s of the display are colored green yellow red and a second red respectively One LED at a time is illuminated The green LED signifies a temperature rise above ambient of up to about 10 degrees centigrade The yellow is illu
39. ltage output at Q to illuminate just the yellow LED The green LED is dimmed at output Q is now low 317 mv is the amount of voltage indicative of a 20 degree centigrade change in sensed temperature If the differential voltage is above about 317 mv then there are high inputs to decoder 75 at both A and B producing a high output at Q which illuminates just the red LED and low outputs at Q and Q which dim the green and yellow LED s The output voltage from amplifier 29 also controls the voltage to frequency device 10 This voltage is offset by the Re 35 554 9 reference voltage preferably about 2 5 v to 3 4 v from VREF91 at comparator 8 to produce the lowest duty cycle of the voltage to frequency node 10 at ambient The output voltage from amplifier 29 causes the voltage to frequency node 10 to pulse the clock of the D flip flop 17 Each time the clock is pulsed the D flip flop 17 has an output Q directly dependent upon input D The output Q is connected to the D input so that after each pulsing of the clock a change in Q will result in a subsequent change in D which in turn produces a change in Q on the next pulse of the clock Thus the D flip flop 17 ensures a 50 duty cycle of the buzzer 86 and the frequency of the D flip flop 17 is generated by the voltage to frequency device 10 In turn as the output voltage from amplifier 29 increases the voltage to frequency device 10 produces a more frequent clocking signal to D f
40. mbly means responsive to a reference temperature signal and sinals signals indicative of radiation levels detected by the sensor for providing on a display an indication of the temperature of a subject above a reference temperature and 10 15 35 45 55 12 a timing circuit means which maintains the detector in operation for a predetermined length of time and there after automatically shuts off the detector said reference temperature signal being reset when the detector is turned on subsequent to its automatically shutting off said timing circuit means comprising a counter a power switch by which a user initially connects a battery to said counter and means for establishing the reference temperature signal an internal switch which is closed after the battery is connected to said counter and means for establishing the reference temperature signal said internal switch closed maintaining the connection of the battery to circuits of the detector thereby allowing a user to release the power switch and the detector to maintain itself in operation state of said internal switch being dependent on an output signal from said timing circuit means and means for producing an audible signal dependent on a control signal from said counter and a second output signal from said timing circuit means said audible signal sounding when said counter reaches a predeter mined count and said timing circuit means thereafter turns off the d
41. minated for a sensed tempera ture rise between about 10 and 20 degrees centigrade The first red LED is illuminated for sensed temperature rise between about 20 and 65 degrees centigrade The second red LED is illuminated for sensed temperature rise above about 65 degrees centigrade Power switch 55 is closed by the user upon operation of the device Power switch 55 connects battery 39 to the lines of the circuit Timer 6 is in turn powered and closes switch 62 for about 0 5 seconds During this interval the negative voltage produced by the IR sensor corresponds to the ambient object at which the device is pointing This voltage is amplified by amplifiers 41 and 44 and stored on capacitor 64 The timer 6 also holds buzzer 43 off and disables the decoder 45 powering the display until the capacitor 64 is charged At the end of the 0 5 seconds the timer 6 opens switch 62 to discontinue the charging of capacitor 64 reset the buzzer 43 and enables the decoder 45 allowing the greed LED to light signifying that the device is autozeroed The negative charge held by capacitor 64 is applied to buffer 46 The negative voltage output of buffer 46 is the autozero reference signal which is later input to differential amplifier 56 with radiation signals from amplifier 44 indica tive of temperatures sensed by sensor 37 For targets emit ting more energy than the autozero reference target amplifier 56 has a positive output and for targets emitting less ener
42. ncrementally selects light emitting diodes based on the high and low reference inputs for that particular driver The incremental change of each driver is defined at a voltage of one tenth of the difference between the high and the lows references there being ten light emitting diodes per driver The light emitting diodes asso ciated with each driver are linearly driven by that driver The low reference of the succeeding driver is set equal to the high reference to the preceding driver The voltage per incremental change of the succeeding driver is then defined by its high and low references which have a different difference than the high and low references of the preceding driver The light emitting diodes selected from one display driver to the next are thus driven in a piece wise linear fashion This results in each driver responding to a single incremental change in the amplified signal for different selections of light emitting diodes but different drivers responding to different incremental changes for different selections of light emitting diodes The display drivers provide a piece wise linear approximation of temperature which is a nonlinear function of the sensed heat flux In the particular embodiment the display driver associ ated with the light emitting diodes for the zero degree to 9 degree end of the bar graph has a low reference to zero mV and a high reference voltage of 150 mV A display driver selects each additional LED in res
43. ponse to a voltage step of Re 35 554 7 15 mV to indicate a temperature change of 1 degree on the bar graph The low reference input to the succeeding driver is 150 mV and the high reference is 320 mV to establish a voltage step of 17 mV for each degree of change on the bar graph between the 9 degree and 19 degree segment The third display driver uses references which account for both the linearization and the change in scale increment in the 20 degree to 100 degree centigrade part of the bar graph The first incremental change at which the third driver responds provides the 1 degree centigrade change in tem perature on the bar graph from 19 degree centigrade to 20 degrees The remaining incremental change with the third driver provide selection of the LEDs for the 10 degree increments in the 20 degree to 100 degree segment of the bar graph A complication arises with the third driver because it must provide a 1 degree increment from 19 degrees to 20 degrees and 10 degree increments thereafter To accomplish this the low reference is set at a level below 320 mV the high reference of the preceding driver and the high refer ence is set at 2 4 volts The third driver therefore responds to approximately 320 mV increments The large incremental change to which the driver responds sets the first trigger level at about 0 106 0 230 or at 0 336 mV This is approxi mately the input to which the second driver would have responded if it had on
44. positive voltage indicative of the difference between the reference tempera ture and the temperature being observed The voltage drives comparators 71 and 73 to produce inputs at A and B ofthe 2 to 4 decoder 75 The second inputs to the comparators are taken from a voltage divider of resistors 87 88 and 89 which divides the reference voltage from the reference voltage generator 91 With low temperatures the output voltage from differential amplifier 29 is less than that across resistor 89 and neither comparator is enabled With somewhat higher temperatures the output voltage surpasses that across resistor 89 and comparator 73 is enabled With yet higher tempera tures the voltage across resistors 87 and 89 is matched and comparator 71 is enabled The decoder 75 selects one of three outputs placing a high voltage on one of three display LED s connected to the decoder outputs If the voltage differential is below about 166 mv then comparators 71 and 73 produce low outputs to the decoder inputs A and B producing a high voltage output of the decoder 75 at which illuminates just the green LED 166 mv is the amount of voltage that would result from detecting a 10 degree centigrade rise in target temperature above ambient If the differential is between about 167 mv and 316 mv then comparator 73 places a high voltage input at A and comparator 71 places a low voltage at input B Those inputs are decoded to produce a high vo
45. pulsing frequency of buzzer 70 Because the display is also triggered by the output voltage from amplifier 67 the increasing pulse frequencies of buzzer 70 correspond to the increasing display indication Ihe buzzer 70 is refrained from sounding upon initial powering of the device by the gate 40 During this time Gate 40 causes the buzzer 70 to sound for one second as the unit shuts itself off Upon initial powering of the device flipflop 31 is set such that its Q output goes low and the 30 second counter 33 is set such that its output is high Through the next 30 seconds the gate 40 has a high voltage 10 15 25 35 45 55 65 6 input from the output of the 30 second counter 33 and a low voltage second input from the Q output of the D Flip Flop 31 These two inputs produce a low voltage output from the gate 40 which disables the sez input D flip flop 32 thus holding the buzzer 70 from sounding so that the buzzer is only sounded with clocking of the flipflop 32 by the voltage to frequency converter 92 After counter 33 counts the 30 seconds during which the unit has been operating the voltage output of counter 33 drops causing the formerly high input to the gate 40 to become a low voltage input Because the other input to gate 40 from the Q output of D flip flop 31 is also low the output of gate 40 becomes a high voltage output and thus enables sets the D Flip Flop 32 The buzzer 70 is thereby sounded upon the ne
46. r as claimed in claim 20 wherein the window comprises germanium 22 A radiation detector comprising a radiation sensor an autozero circuit means which establishes a reference signal and subtracts it from a radiation signal indicative Re 35 554 15 of sensed radiation to provide a display signal the autozero circuit means comprising a time controlled switch which enables voltage being produced by the radiation sensor initially detecting a reference target at ambient temperature to be placed on a capacitor for a certain amount of time after initial detection of ambient temperature and thereafter disables the placing of volt age on the capacitor the voltage charging the capacitor to a level indicative of detected ambient temperature such that the charged capacitor provides a reference signal corresponding to the ambient temperature a selectively actuated display assembly having a display of different colored LED s the assembly being respon sive to the display signal to drive the display to provide an indication of the amount of radiation sensed by the radiation sensor as a difference between the reference signal and the radiation signal and to be indicative of the sensed radiation one LED of the display being initially illuminated when the time controlled switch disables the placing of voltage on the capacitor signi fying to a user that the detector has been autozeroed a means for controlling said time controlled switch and se
47. r as claimed in claim 32 wherein said filtering means blocks wavelengths of about 1 5 microns and less 36 A radiation detector as claimed in claim 32 further comprising sound generator means for producing an audible signal having a pulse frequency that increases in correspondence with increases in temperature detected by the sensor and indicated in the display 37 A radiation detector as claimed in claim 32 wherein said display assembly means comprises a bar graph display comprising red yellow and green groups of light indicators the light indicators representing incremental temperature differences 38 A radiation detector as claimed in claim 32 wherein the display assembly means comprises a green LED for indicating temperature from about zero degrees centigrade to about 10 degrees centigrade a yellow LED for indicating temperature from about 10 degrees centigrade to about 20 degrees centrigrade and a first red LED for indicating temperature from about 20 degrees centigrade and greater and wherein only one LED is illuminated at a time 39 A radiation detector as claimed in claim 38 wherein the first red LED indicates temperature from about 20 degrees centrigrade to about 65 degrees centigrade the display assembly further comprising a second red LED for indicating temperature from about 65 degrees centigrade and greater 18 40 A radiation detector as claimed in claim 32 wherein said detector is adapted to detect temperature vari
48. re from about 20 degrees centigrade and greater and wherein only one LED is illuminated at a time 68 A radiation detector as claimed in claim 67 wherein the first red LED indicates temperature from about 20 degrees centigrade to about 65 degrees centigrade the display assembly further comprising a second red LED for indicating temperature from about 65 degrees centigrade and greater 69 A radiation detector comprising a housing adapted to be hand held during use of the detector a radiation sensor positioned in the housing for sensing radiation from a target through one end of the housing and generating a sensor signal indicative of the sensed radiation an autozero circuits which establishes a reference signal indicative of an ambient temperature in response to the sensor signal received by the radiation sensor and an amplifier that drives a sound generator means respon sive to the radiation sensor and the reference signal for producing an audible signal having a pulse frequency that increases with increase in temperature of the target 10 45 55 60 65 22 70 A radiation detector comprising a radiation sensor generating a radiation signal indica tive of sensed radiation an autozero circuit means responsive to the radiation sensor for automatically establishing a reference signal indicative of a reference temperature when the detector is turned on said autozero circuit means summing said reference signal wi
49. said means for filtering out short wavelengths filters out wave lengths of reflected sun light and other visible light 29 A method of sensing radiation the steps comprising zeroing a radiation detector by detecting with the detector radiation indicative of an ambient temperature scanning a target area with the radiation detector the detector having a display and an audible signal indica tive of sensed temperature difference between a tem perature corresponding to an amount of detected radia tion during the scanning and the previously detected ambient temperature locating a subject within the target area by noting the subject at which the detector is pointing when the audible signal reaches a certain state and providing a quantitative indication of temperature differ ence between the ambient temperature and temperature of the located subject using the display of the radiation detector 30 A method as claimed in claim 29 further comprising the step of filtering out short wavelengths on the order of less than about 1 5 microns while allowing longer wavelengths of interest to be sensed by the radiation detector 31 A method as claimed in claim 29 wherein the step of providing a quantitative indication includes providing a bar graph display of the temperature difference 32 A radiation detector comprising a housing adapted to be hand held during use of the detector a radiation sensor positioned in the housing for sensing r
50. ses with increasing radiation sensed by the radiation sensor and indicated by the display means and an amplifier for driving the multicolor display means and the sound generator means and for generating the difference signal in response to the reference signal and the radiation signal 61 A radiation detector as claimed in claim 60 wherein said filtering means is a long wave pass filter which starts passing light at wavelengths in the range of about 1 5 microns and greater generated by sources of interest 62 A radiation detector as claimed in claim 60 wherein the filtering means comprises a lens 63 A radiation detector adapted for scanning of a target area comprising a housing adapted to be hand held during the use of a detector a radiation sensor positioned in the housing for sensing radiation received through one end of the housing a multicolor display means for providing a visual indi cation of the radiation sensed by the sensor in green yellow and red segments of an LED display the display means comprising a green LED for indicating temperature corresponding to sensed radiation from about zero degrees centigrade to about IO degrees centigrade a yellow LED for indicating temperature corresponding to sensed radiation from about 10 degrees centigrade to about 20 degrees centigrade and a first red LED for indicating temperature correspond ing to sensed radiation from about 20 degrees centi grade and greater only one
51. th said radiation signal to produce a display signal a display assembly means responsive to the display signal for providing on a display an indication of the tem perature of a subject above said reference temperature and a timing circuit means which maintains the detector in operation for a predetermined length of time and thereafter automatically shuts off the detector said reference signal being reestablished when the detector is turned on subsequent to its automatically shutting off 71 A radiation detector comprising a radiation sensor means responsive to the sensor for generating a reference signal indicating radiation levels a bar graph display providing a visible temperature indication at temperatures substantially less than a flame an amplifier for driving the display in response to an amount of radiation sensed by the radiation sensor and the reference signal a filter attenuating short wavelengths on the order of less than about 1 5 microns while allowing longer wave lengths in a range above about 1 5 to 3 microns and greater generated by sources of interest to be sensed by the radiation sensor and a housing having an opening for enabling entrance of radiation the filter being supported by the housing to filter the radiation and the sensor being supported by the housing to detect the radiation filtered by the filter the display being supported by the housing to present its visible temperature indication the hous
52. the sensor is directed at the light source 28 Having been automatically zeroed at the ambient temperature the indication 20 provides a reading of the temperature rise above ambient The maximum reading is the measurement of interest and such reading is much more readily picked up by an observer using a bar graph display than a digital numerical display The electrical schematic diagram of the electrical circuit used in one embodiment of the invention is illustrated in FIG 4 The unit is self operated for a predetermined length of time after the initial powering of the unit by way of a timing circuit which includes a 30 second counter 33 In this embodiment the initial powering of the unit begins by the user squeezing the side of the housing 14 of FIG 1 Upon squeezing the housing power is applied from the battery 82 through the switch SW of FIG 4 to the V regulated line which begins the counter 33 The switch SW is manually held closed by the user long enough for the high voltage across the V regulated line to close switch K1 through coil K2 connected to switch K1 Switch After the switch SWI opens switch K1 maintains connection of the 9 V Battery 82 to lines not shown powering the rest of the circuit Switch SW is connected to switch SW and thereby is closed at the same time The closing of switch SW resets and powers up the autozero circuit 48 and sets D flip flop 31 The autozero circuit 48 as will be described later pro
53. tility company guidelines Further in another design of the invention the display includes the three colored segments but is not illuminated to give a full bar indication rather just a single level indication is displayed In another design of the invention the display has two seg ments colored red in addition to a green and yellow segment The first red segment displays temperatures between about 20 degrees centigrade and 65 degrees centigrade The sec ond red segment displays temperatures above about 65 degrees centigrade In another design of the invention a pulsed audible signal sounds at a different pulse frequency for each colored segment of the bar graph display The pulse frequency increases as the detected temperature rise increases A switch to disenable the audible signal is also available in another design of the invention FIG 2 illustrates an example of the use of the device to scan a region to pinpoint a source of maximum radiation While directed to a neutral surface as in position 24 the indication 20 is set at a low region of the scale The indication 20 is automatically zeroed at this level and the radiation sensor is then scanned across a wide field to a position 26 Within that field the sensor senses radiation Re 35 554 5 from the light source 28 As indicated by the scale position shown schematically between the two end positions 24 and 26 the indication 20 rises to a maximum level at the position 30 at which
54. time controlled means 12 A radiation detector as claimed in claim 11 wherein said time controlled means for establishing a reference signal includes placing a voltage on a capacitor the voltage being produced by the radiation sensor initially detecting a reference target 13 A radiation detector as claimed in claim 11 2 wherein said means for controlling said time controlled means comprise timing means comprises a timer coupled to a switch zhe time controlled means which enables a reference signal voltage to be placed on the capacitor for a certain amount of time after initial detection of an ambient target and thereafter disables the placing of said reference signal voltage on the capacitor after the certain amount of time the timer providing an output voltage drop which enables the display assembly means to illuminate one seg ment of the display signifying to a user that the detector has been autozeroed 14 A radiation detector as claimed in claim 13 further comprising means for producing an audible signal which corresponds to the amount of radiation sensed by the sensor and above an ambient level which is indicated on the display a pulse frequency of the audible signal increasing 5 10 15 35 45 50 55 65 14 for each increase in amount of sensed radiation indicated by the display where wherein the timer disables the audible signal producing means from to inhibit the sounding of the audible signa
55. ut 20 degrees centigrade and about 65 degrees centigrade The second red segment indi cates a temperature rise above about 65 degrees centigrade The same autozero circuit is used as in the foregoing embodiments to establish a reference signal The sum of the reference signal and a subsequent radiation signal indicative of the amount of sensed radiation drives three comparators to produce inputs to a 3 to 8 decoder which selects one of the four LED s The three comparators and 3 to 8 decoder operate in the same manner as the two comparators and 2 to 4 decoder in the other design where higher temperatures enable an additional comparator which in turn causes the decoder to illuminate a respective LED Further a buzzer sounds in reference to the four LED s as the buzzer did in the three LED embodiment with a constant tone sounding for sensed temperatures above about 20 degrees centigrade A switch to disenable the buzzer allows the user to scan a subject without the audible signals In accordance with another aspect of the invention a germanium window is used to cover the radiation sensor The window filters out sunlight energy but allows the sensor to respond to the heat energy of the subject or of a flame the heat energy being at a longer wavelength than the sunlight energy This filtering ensures greater accuracy of the device BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other objects features and advantages of the invention will b
56. utozero circuit establishes a reference signal by placing charge on a capacitor through a time controlled switch The switch is closed by a timer upon the turning on of the device The closed switch allows charge to be placed on the capaci tor The timer holds the switch closed just long enough to charge the capacitor to a level indicative of the temperature of the sensed reference The timer also disenables the buzzer and display until the capacitor is charged to the level indicative of the temperature of the sensed reference When the timer opens the switch to the capacitor the display and buzzer are enabled and the display illuminates signifying the autozeroing of the unit During a subsequent scan of the subject the autozero circuit sums the reference signal with a radiation signal indicative of the amount of sensed radiation and this sum provides a display signal In another design of the invention a low cost circuit embodies the autozero circuit and a display of 3 LED s signifies safe caution and danger readings In the display only one LED at a time is illuminated The autozero circuit is like the one described above During a subsequent scan of the subject the reference signal establishes by the autozero circuit is summed with the radiation signal indicative of the amount of sensed radiation This sum drives two compara Re 35 554 3 tors to produce inputs to a 2 to 4 decoder which selects one of the three LED s The second
57. xt clocking of D flip flop 32 from the voltage output of the voltage to frequency device 92 The Q output from D Flip Flop 31 is delayed from changing voltages a second time low to high by the 1 Hz oscillator 42 After 1 second D Flip flop 31 is clocked by the 1 Hz oscillator and the Q output from D Flip Flop 31 changes from a low to a high voltage thus causing dissimilar inputs to the gate 40 and disabling fhe set input to the D Flip Flop 32 from further sounding the buzzer 70 Thus just before the unit shuts itself off the buzzer sounds one last time The drop in voltage of the voltage output of counter 33 not only sounds the buzzer 70 but also changes the Q output of D flip flop 31 from high to low This low voltage causes coil K2 to open switch K1 and thereby shuts off the unit A subsequent squeeze of the housing 14 resets the autozero reference signal held in buffer 47 and the 30 second counter 33 in the same manner as described above for initial pow ering of the device Display 78 operates as follows The signal from the thermopile sensor element 83 is amplified in a preamplifier 69 At the summing node 66 the radiation signal from the thermopile is summed with the reference signal from the autozero circuit to be described The sum is amplified in an amplifier 67 Each display driver in display 78 responds to the amplified signal and incrementally selects light emitting diodes to light the bar graph display Each display driver i

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