REMOTE MEASUREMENT OF INTERNAL TEMPERATURES THROUGH MATERIALS PENETRABLE BY MICROWAVE RADIATION

Abstract: A method and an apparatus remotely measures internal temperatures through materials penetrable by microwave radiation. Higher temperature areas for example in high voltage equipment may be detected through procelain clad insulators whereas most detector systems only measure the outside surface. The method comprises selecting a frequency range where the microwave radiation at least partially penetrates the materials, detecting self emitted thermal radiation through the materials for the microwave frequency range in a target beam of a passive receiver, producing signals proportional to the thermal radiation detected in the target beam, remotely scanning the target beam of the passive receiver through a target pattern, comparing the signals for different locations in the target pattern to identify locations emitting higher thermal radiation, and processing the signals to provide an indication of internal temperature for the locations emitting higher thermal radiations.

Description: REMOTE MEASUREMENT OF INTERNAL TEMPERATURES THROUGH MATERIALS PENETRABLE BY MICROWAVE RADIATION Technical Field The present invention relates to remotely determining internal temperatures through materials penetrable by microwave radiation using microwave radiometric techniques . More specifically the present invention relates to monitoring porcelain and polymer clad high voltage equipment. The present invention also relates to detection of forest fires and locating persons in search and rescue operations, and law enforcement operations. Background Art High voltage equipment failure is a major component in the maintenance costs of electrical transmission and distribution systems. Such equipment includes: protective devices such as surge arrestors, current transformers, potential transformers, capacitance voltage transformers (CVT's) and potheads. In most of this equipment porcelain or polymer insulators are used for housing the insulation system or the active elements of a protective device. Many equipment failures can be attributed to failure of the insulation system of transformers and capacitors, or the active elements of protective devices. The failures are usually due to incipient faults that develop over a period of time, and are frequently accompanied by partial discharge and localized heating. Thus, there is a need to monitor and determine internal temperatures of the equipment to determine the general condition. Various methods have been attempted for monitoring the temperature of high voltage equipment such as infrared thermography and the use of fibre optic transducers. However, the detection of hot spots by infrared imaging is generally limited to measurement of the surface temperature, thus, when an increase in surface temperature is discovered, the equipment is generally in the advanced stage of failure. With regard to fibre optics, whereas these systems work, they have to be factory installed. Retrofitting existing equipment in service is costly and not practical. The monitoring of each and every piece of equipment by means of a fibre optic sensor would result in a colossal monitoring system for porcelain and polymer clad insulator devices in an electrical system. Moreover, problems associated with the compatibility of the materials and the aging and eventual failure of the optical fibres may occur. /14941 P I - 3 - Disclosure of Invention It is an aim of the present invention to provide a non-invasive method and a system for remotely measuring internal temperature of porcelain and polymer clad devices. The present invention also relates to detection of forest fires and locating persons in search and rescue operations, and law enforcement operations. By being able to monitor internal temperatures remotely avoids the necessity of having to approach and contact each device. One cannot approach and contact high voltage equipment without shutting off the power, thus causing power interruptions to the end user. It is a further aim of the present invention to be able to determine the internal temperature remotely through materials that are semi-transparent to microwaves, or at least partially semi-transparent. An example of a need to determine internal heat through materials would be buildings, enabling one to determine whether there is a location of high temperature within a building which might indicate a fire. Also by placing a monitor in an airplane or a satellite, one is able to determine whether forest fires or hot spots (i.e., kindling sites) exist after forest fires have been put out . Another use for determining hot internal temperatures is search and rescue operations, such as locating persons in collapsed buildings after earthquakes, bombing or other collapses, locating persons buried by avalanches, landslides and other disasters. Thus, it is an aim of the invention to provide a system to scan remotely with a passive receiver to detect thermal radiation that might indicate a person or a fire and to find locations emitting higher thermal radiation. Another use of the present invention is to remotely scan in medical treatment for hypothermia conditions to determine internal temperature of the different body organs, also to locate cancerous tumours within a body. In each case the locations of higher thermal radiation can be determined. Yet a further use of the present invention is detection of forest fires and locating people in search and rescue and law enforcement operations. Still further uses of the present invention include measuring temperatures of chemical reactions in corrosive environments, measuring temperature of hazardous materials and infectious waste materials during destruction processes. The present invention provides a method of remotely measuring internal temperatures through materials penetrable by microwave radiation, comprising the steps o : selecting a frequency range where the microwave radiation at least partially penetrates the materials; detecting self emitted thermal radiation through the materials for the microwave frequency range in a target beam of a passive receiver; producing signals proportional to the thermal radiation detected in the target beam; remotely scanning the target beam of the passive receiver through a target pattern; comparing the signals for different locations in the target pattern to identify locations emitting higher thermal radiation, and processing the signals to provide an indication of internal temperature for the locations emitting higher thermal radiation. The present invention also provides a device for remotely measuring internal temperatures through materials penetrable by microwave radiation comprising: a passive receiver to detect thermal radiation for a predetermined microwave frequency range in a target beam; scanning means for the receiver to remotely scan the target beam through a target pattern, such that the receiver produces signals proportional to the thermal radiation through the materials in different locations of the target pattern, and comparative means to compare the signals from the different locations as the target beam scans to produce an indication of temperature differences in the different locations. Brief Description of Drawings In drawings which illustrate embodiments of the present invention, Figure 1 is a schematic drawing of a typical measurement set up for detection of internal hot spots showing a passive microwave radiometer according to one embodiment of the present invention with a target beam from an antenna, Figure 2 is a block diagram of a passive receiver radiometer according to one embodiment of the present invention, Figure 3 is an isometric view showing a mounting and scanning arrangement for a passive microwave radiometer according to one embodiment of the present invention, Figure 4 is a graph showing temperature difference in vertical distance for a porcelain column containing a string of silicon carbide blocks with two heated elements therein, Figure 5 is a graph showing temperature difference in vertical distance for a porcelain column containing a string of zinc oxide blocks with two heated elements therein, Figure 6 is a graph showing temperature difference in vertical distance for a porcelain column containing heated oil/paper insulation therein, Figure 7 is a graph showing radiometric temperature as a function of physical temperature of zinc oxide blocks, Figure 8 is a graph showing radiometric temperature as a function of physical temperature of silicon carbide blocks, Figure 9 is a thermal image representing temperature gradients for a target pattern, Figure 10 is a thermal profile of a test of burning charcoal covered by forest duff, Figure 11 is a thermal image of a person behind a wall taken from about 10 metres. Modes for Carrying Out the Invention A scanning device is illustrated in Figure 1 having a microwave radiometer 10 attached to the back of a dish antenna 12 having an antenna pattern 14 as illustrated. A narrow target beam 16 represents the antenna receiving beam in which the passive receiver 10 detects thermal radiation. The beam 16 is shown aimed at an insulator 18 formed of porcelain or polymer which has inside it a series of metal oxide or silicone carbide blocks 20 to absorb excess energy. These blocks absorb energy from lightning strikes and other electrical surges and thus heat up. Positioned at the center of the antenna dish 12 is a laser pencil 22 which projects a coloured laser beam onto the surface of the insulator 18. The laser beam 24 provides a pin point light on the surface to enable an operator to aim the narrow target beam 16 and ensure it is directed at the insulator 18. By moving the antenna 12 the laser beam 24 also moves so the pin point light changes position on the insulator 18 and this is visible from a considerable distance. Whereas a laser pencil 22 and laser beam 24 are shown as being one system for aiming or positioning the antenna 12, other aiming devices such as a sighting telescope may also be provided so an operator knows the exact location where the narrow beam 16 is observing. The description and drawing illustrated herein shows an insulator 18, however, this could be a building with walls of wood, concrete or other materials that permit at least partial penetration of microwaves. In the measurement of internal temperature, it is necessary to compare the temperature of one target location with other locations in a general target pattern on the insulator or the like. Thus, a scanning action occurs across different locations to determine temperatures at each of these locations. The locations that do not have internal heat points can be compared with locations that do have internal heat points. By scanning the beam up and down or sideways over an insulator 18, then the radiometer 10 initially detects the temperature of the porcelain insulator at the location where there is no internal hot spots, but as the scan progresses, the target beam is aimed at the heated blocks 20 within the insulator 18 and an increase in thermal radiation is detected. Surrounding objects have an effect on the signals. The ground, the sky and other surrounding objects such as trees and the like all affect the value of the signal received by the receiver 10. Thus, by scanning the target beam in a target pattern, one is able to determine differences in thermal radiation from different locations in the target pattern and these signals are used to provide comparisons which are proportional to temperature. The radiometer 10 as shown in more detail in Figure 2, is of the type known as a Dicke radiometer known in the prior art and specific reference is made to this type of radiometer in a textbook entitled "Microwave Remote Sensing Active and Passive" by Ulaby et al, Volume 1, Artech House, Norwood, published 1981. As shown in Figure 2 the antenna 12 detects thermal radiation in the microwave frequencies. In one embodiment the antenna is a parabolic dish antenna with a center frequency of 17 GHz, 36" diameter feed type Cassegrain, a gain of 40 dB minimum and a maximum beam width not more than 1.4° at the 3 dB level. The signal from the antenna is modulated by a ferrite Dicke switch with driver 32. the modulation consists of periodically switching the receiver input between the antenna 12 and a constant reference noise temperature source 36 at a switching rate higher than the highest significant spectral component in the gain variation spectrum. A switching frequency of 98.2 Hz was chosen so that over a period of one cycle the system gain is essentially constant, and therefore identical for the half cycle to which the receiver is connected to the antenna 12 and the half cycle when the receiver is connected to the reference source 36. The components of the radiometer 10 were mounted on aluminum plate attached to the antenna 12 as shown in Figure 1. The radiometer 10 is enclosed in a thermally insulated constant temperature enclosure 38 maintained at /14941 - 11 - 20.5°C within 0.01°C by means of a thermoelectric cooler 40. A small fan (not shown) mounted inside the enclosure keeps the air temperature uniform. The temperature of the reference source 36 was controlled by means of a heating jacket 42 surrounding the termination. The heating jacket 42 was insulated and the temperature of the reference termination was maintained stable within 0.01°C. To maintain the Dicke radiometer in a balanced state the pulsed noise injection system was used. In this configuration null balancing is achieved by noise injection from a noise diode 43 into the antenna signal through a cross arm directional coupler 44 in the form of narrow pulses controlled by the PIN switch 46 via the feedback circuit. The integrator 48 and feedback amplifier 50 drive a voltage controlled oscillator 52 which in turn drives a pulse generator 54 which drives the PIN switch 46. The switching frequency is controlled by the feedback loop to provide the necessary amount of noise that a null condition is maintained at the input of the integrator 48. The frequency of the pulses is linearly related to the antenna temperature. The radiometer 10 has a first low noise amplifier 56 operating within a frequency of 16-18 GHz, a pass band filter 58 having a center frequency of 17 GHz with a band width of 2± 0.2 GHz. Thus the filter takes out all signals outside the 16 to 18 GHz range and thus is a preferred range for determining internal temperatures of porcelain and polymer clad devices. The filtered signal is further amplified by a second stage low noise amplifier 60 and detected by a crystal detector 62 which provides an output signal that is fed through a synchronous demodulator 64 modulated at the switching frequency of the Dicke switch 32. A frequency counter 66 such as a monitoring screen or other visual indication system displays the thermal radiation. Other techniques may be used to continuously maintain a Dicke radiometer in a balanced state including reference channel control, antenna channel noise injection and gain modulation. The scanning mechanism is shown in more detail in Figure 3. The antenna 12 and radiometer 10 are mounted on an H-frame 60. A worm gear arrangement 62 joined to a mounting bracket 64 for scanning in a vertical direction and a rotary arrangement 66 rotates the mounting bracket 64 on the H-frame 60 in a horizontal plane. The laser pencil 22 is used for aiming the antenna. The post processing and display 68 permits areas of higher thermal radiation to be seen in the form of graphs, contour plots or thermal image pictures. In another embodiment, a first motor 70 drives the worm gear arrangement 62 and a second motor 72 drives the rotary arrangement 66. A computer 74 associated with the post processing and display 68 provides signals for the antenna 12 to scan through a predetermined pattern. Processing of the signals are then arranged to provide a pattern image on a screen so that areas that emit higher thermal radiations are displayed. For determining hot spots in porcelain or polymer clad equipment or in any measurement of the temperature of underlying structures, it is necessary to determine the frequency dependence of the dielectric properties of the cladding of the device, sensitivity and stability, spatial resolution as well as cost and size. Ideally, the best situation is when the housing of the device is transparent to microwave radiation. However, it has been found that permittivity of most materials is a function of frequency, thus tests must be conducted in order to determine a selection of operating frequencies for the radiometer. Complex permittivity of porcelain may be measured in the frequency range of 8 to 40 GHz. The advantages of operating at higher frequencies are the high spatial resolution and the smaller size of the antenna and the microwave components. At lower frequencies the porcelain is more transparent to the microwaves, however, good spatial resolution can only be achieved using a large antenna. An operating frequency between 16 to 18 GHz was considered a compromise between size and resolution and losses in the porcelain. This range is sufficiently far from the water absorption line. The spatial resolution of this technique is determined mainly by the beam width of the antenna. The beam width is a function of the aperture size and frequency. In the present embodiment the system was optimized for detecting hot spots within porcelain clad devices and the operating frequency was chosen so that losses within the porcelain do not present a problem using a reasonable size antenna with good spatial resolution. For applications involving polymer or fibre clad devices, the microwave radiation would be more penetrating over a wider frequency range and smaller size antenna may be used. In order to test the radiometer a station class surge arrestor was disassembled and the blocks removed. A heater wire was sandwiched between two blocks as illustrated in Figure 1. Thermally conducting epoxy was used to keep the heater wire in position. The stack of surge arrester blocks was then placed inside the porcelain housing with styrofoam insulation between the heated blocks and the cold blocks. The physical temperature of the hot spot was monitored by means of a thermocouple attached to the heated blocks. To simulate a hot spot inside oil/paper insulation, sheets of kraft paper were folded in the form of a cylinder and immersed in transformer oil in a cylindrical glass container. Heating was accomplished by a wire heater immersed directly in the oil inside the paper cylinder. The whole assembly was then placed inside the porcelain column. The radiometer was operated in the 16 to 18 GHz having a center frequency of 17 GHz and a modulation frequency of 98.2 Hz. ΔT (Dicke mode) is 0.027°C for 100 msec integration time ΔT (nulling mode) is 0.022°C for 200 msec feedback loop time constant. The antenna was a Cassegrain type with an aperture of 36" and a beam width less than 1.4° and a gain of 40 dB. Tests were carried out on zinc oxide surge arrester blocks, silicon carbide surge arrester blocks and paper/oil insulation. The measurements were carried out with the radiometer operating in the Dicke mode and in the nulling mode. The measurements were also carried out with lights on and lights off to examine the effects of reflection and background radiation. In the balance mode the reference temperature is always higher than the temperature of the scene, therefore T ref - T A gets smaller near the hot spot, whereas in the unbalanced mode T A - T re£ gets larger near the hot spot. Figure 4 shows the response of the radiometer in an unbalanced state looking at a porcelain column containing a string of silicon carbide blocks with two elements heated electrically and the room lights on. The first and lowest temperature is the room temperature and represents no electric heating. Figure 5 shows the response of a balanced radiometer looking at a porcelain column containing a string of zinc oxide blocks with two of the blocks heated electrically and the lights on. Figure 6 shows the response of a balanced radiometer looking at a porcelain column containing oil/paper insulations heated electrically. Figures 7 and 8 show the temperature dependence of the radiometric temperature for zinc oxide and silicon carbide blocks. The materials show a non-linear behaviour making the materials radiometrically more visible at higher temperature. This phenomenon enhances the sensitivity of the technique to zinc oxide or silicon carbide malfunction. Figure 9 shows a two dimensional thermal image illustrating contour plot of the internal temperature of a 500 kV current transformer. The intensity readings are shown with the lightest or white area representing the hot area and the darkest or black representing the coolest area. The two dimensional plan represents linear units for width and height. The tests show that microwave radiometric techniques for remote measurement of internal temperatures of porcelain and polymer clad devices are successful since radiation at microwave frequencies can penetrate moderately lossy materials, thus internal temperatures can be determined by measuring the emitted microwave power through the lossy materials. For use in the field, a portable radiometer with small dish antenna or a phaser ray can be used with a sighting device such as a laser pencil permitting an operator to move the antenna by hand scanning backward and forward to determine hot spots in an insulator or other object that has penetrable materials in front thereof. The scanning mechanism scans in a predetermined pattern which is recorded and provides an image of higher thermal readings at specific locations in the pattern. Thus, while the present description of the use of the device for measuring internal temperatures is for insulators, it will be apparent to those skilled in the art that this system would equally well apply for determining the presence of, for example, a person within a building, for locating individuals buried by fallen buildings caused by earthquakes, bombing incidents or collapse of buildings, and to locate fires within buildings. The antenna may be mounted in an aircraft for scanning forests to determine hot spots with a mechanical and/or electronic scanning system linked to a computer to provide exact locations where hot spots occur. The radiometer also has uses in the medical field. A hand held radiometer may be used for scanning and a pin point positioner used to locate an area of increased thermal radiation within the body. Underground or unseen forest fires can be detected remotely by scanning in the frequency range from about 0.5 GHz to 16 GHz. The device for remotely scanning may be hand held or mounted on a vehicle or in an aircraft. When mounted in an aircraft the microwave frequency can be in the range of about 0.5 GHz to 40 GHz. In this latter case the device may also be positioned on a mountain top or on top of an observation tower to constantly monitor forest fires. Figure 10 illustrate an example of use of the device. The graph illustrates the thermal profile of burning charcoal covered with forest duff so the hot spot cannot be seen. This profile was obtained from the device positioned 10 metres away. The position figures are linear units. In another embodiment the device for remotely measuring internal temperatures through materials penetrable by microwave radiation is used for locating people inside buildings and houses. The device may be used for law enforcement, search and rescue operations. The device may be hand held or mounted in a vehicle or aircraft, the preferred frequency range is from about 0.5 GHz to 16 GHz. Figure 11 illustrates the image obtained by the device of a person which is seen through a drywall. A target pattern produces a thermal image of a house or building and can detect a fire. The device also can determine the extent of the fire. Hot spots in walls, ceilings of houses and buildings, due to electrical faults or excess heat produced in heating or ventilating equipment. Security of buildings may also be monitored by the device of the present invention. The presence of intruders or burglars behind walls can be detected by scanning in the frequency range of about 0.5 GHz to 16 GHz. Whereas the present invention discloses detecting with a single target beam and scanning the target beam through a target pattern. In another embodiment a plurality of phase arrays or multiple detectors and antennas pointed in a series of different target beams to form a target pattern are provided. In the case of a hand held unit, there is provided the scanning arrangement which moves either a single or multiple detectors to see different parts of the scene to create real time images in the form of pictures. For different frequencies different sized antennas are required. The selection of the frequency is dependent partly upon the materials to be penetrated by microwave radiation for determining internal temperature and partly by the distance, range and required spatial resolution. For example, if the radiometer were used on a human body, then a small diameter antenna would be used. Whereas an antenna in the form of a parabolic dish is illustrated in the drawings, electronic scanning by phase arrays or multiple detectors may be utilized in place of a parabolic antenna. Various changes may be made to the embodiments described herein without departing from the scope of the present invention which is limited only by the following claims .

Claims: The embodiments of the present invention in which an exclusive property or privilege is claimed are defined as follows : 1. A method of remotely measuring internal temperatures through materials penetrable by microwave radiation, comprising the steps of: selecting a frequency range where the microwave radiation at least partially penetrates the materials; detecting self emitted thermal radiation through the materials for the microwave frequency range in a target beam of a passive receiver; producing signals proportional to the thermal radiation detected in the target beam; remotely scanning the target beam of the passive receiver through a target pattern; comparing the signals for different locations in the target pattern to identify locations emitting higher thermal radiation, and processing the signals to provide an indication of internal temperature for the locations emitting higher thermal radiation. 2. The method of remotely measuring internal temperatures according to claim 1 including monitoring position of the target beam to identify the location from where the thermal radiation occurs . 3. The method of remotely measuring internal temperatures according to claim 2 wherein the position of the target beam is monitored by a laser pencil . 4. The method of remotely measuring internal temperatures according to claim 1 wherein the remotely scanning step is conducted with a dish antenna mechanically sweeping the target pattern. 5. The method of remotely measuring internal temperatures according to claim 4 wherein the dish antenna has motorized movement means and wherein the scanning step is controlled by computer means through the target pattern. 6. The method of remotely scanning internal temperatures according to claim 5 wherein the signals for the different locations in the target pattern are displayed in a pattern image showing locations emitting higher thermal radiation. 7. The method of remotely measuring internal temperatures according to claim 1 wherein the remotely scanning step is conducted with a phase array which electronically scans the target pattern. 8. The method of remotely measuring internal temperatures according to claim 4 wherein the target beam has a beam width of not more than 1.4°. 9. The method of remotely measuring internal temperatures according to claim 1 wherein the microwave frequency range is from about 8 to 40 GHz and is applied to porcelain or polymer clad devices. 10. The method of remotely measuring internal temperatures according to claim 1 wherein the microwave frequency range is from 16 to 18 GHz and is applied to porcelain clad devices. 11. The method of remotely measuring internal temperatures according to claim 1 wherein detecting self emitted thermal radiation through the materials occurs in a plurality of target beams. 12. The method of remotely measuring internal temperatures according to claim 1 occurs in the frequency range of about 0.5 GHz to 16 GHz and the self emitted thermal radiation is from underground or unseen forest fires. 13. The method of remotely measuring internal temperatures according to claim 12 wherein detecting self emitted thermal radiation is by a hand held device. 14. The method of remotely measuring internal temperatures according to claim 12 wherein detecting self emitted thermal radiation is by a device mounted in a vehicle or an aircraft . 15. The method of remotely measuring internal temperatures according to claim 1 occurs in the frequency range of about 0.5 GHz to 40 GHz, and the detecting is by a device mounted on an aircraft, a mountain top or an observation tower to monitor forest fires or locate lost persons. 16. The method of remotely measuring internal temperatures according to claim 1 occurs in the frequency range of about 0.5 GHz to 16 GHz, and the detecting is by a device that is hand held, mounted in a vehicle or mounted in an aircraft, to locate people inside houses, or buildings, to create thermal images of homes and buildings on fire and map the extent of the fire, and to detect the presence of persons behind walls. 17. The method of remotely measuring internal temperatures according to claim 1 occurs in the frequency range of about 1 GHz to 16 GHz to detect hot spots in walls, floors, ceilings of houses and buildings due to electrical faults, or heating and ventilating equipment faults. 18. The method of remotely measuring internal temperatures according to claim 1 occurs in the frequency range of about 0.5 GHz to 12 GHz to monitor internal temperature of lumber and other materials during drying to prevent excessive heating. 19. The method of remotely measuring internal temperatures according to claim 1 wherein the locations emitting higher thermal radiation are identified with a thermal image picture. 20. A device for remotely measuring internal temperatures through materials penetrable by microwave radiation comprising: a passive receiver to detect thermal radiation for a predetermined microwave frequency range in a target beam; scanning means for the receiver to remotely scan the target beam through a target pattern, such that the receiver produces signals proportional to the thermal radiation through the materials in different locations of the target pattern, and comparative means to compare the signals from the different locations as the target beam scans to produce an indication of temperature differences in the different locations. 21. The device for remotely measuring internal temperatures according to claim 20 wherein the materials penetrable by microwave frequencies are porcelain or polymer clad devices and the predetermined microwave frequency range is from about 8 to 40 GHz. 22. The device for remotely measuring internal temperatures according to claim 20 wherein the materials penetrable by microwave frequencies are porcelain clad devices and the predetermined microwave frequency range is approximately 16 to 18 GHz. 23. The device for remotely measuring internal temperatures according to claim 20 wherein the scanning means comprises a dish antenna. 24. The device for remotely measuring internal temperatures according to claim 23 including a laser pencil aligned with the dish antenna to provide an indication of location where the target beam is directed. 25. The device for remotely measuring internal temperatures according to claim 20 wherein the scanning means comprises a phase array to provide electronic scanning. 26. The device for remotely measuring internal temperatures according to claim 23 wherein the target beam has a beam width of not more than 1.4°. 27. The device for remotely measuring internal temperatures according to claim 23 wherein the passive receiver is a Dicke radiometer. 28. The device for remotely measuring internal temperatures according to claim 27 wherein the Dicke radiometer is a balanced radiometer with pulse noise feedback. 29. The device for remotely measuring internal temperatures according to claim 27 wherein the Dicke radiometer has a pass band filter. 30. The device for remotely measuring internal temperatures according to claim 20 including a plurality of passive receivers for a plurality of target beams to provide a target pattern. 31. The device for remotely measuring internal temperatures according to claim 20 wherein the device is hand held. 32. The device for remotely measuring internal temperatures according to claim 20 wherein the device is mounted in a vehicle or in a plane. 33. The device for remotely measuring internal temperatures according to claim 20 wherein the frequency range is about 0.5 GHz to 40 GHz.

Inventors: ABDOLALL KHALED, ABDOLALL, KHALED
Applicants: ABDOLALL KHALED, POWERTECH LABS INC, ABDOLALL, KHALED, POWERTECH LABS INC.
Application year: 1996
Main classification: G01K11
IPC codes: G01K11