Abstract: A metal or graphite fiber is suspended in a working fluid having a high refractive index change with the temperature and a modulated laser beam heats the fiber producing a synchronous thermal wave in the fiber whose amplitude and phase are measured by passing a probe laser beam through the liquid close to the fiber and converting the probe beam deflections into an electric signal. A theoretical model of the thermal wave is used to calculate the amplitude and phase shift of a theoretical thermal wave for points along the fiber from physical characteristics of the lasers and the fiber including an estimate of the thermal conductivity of the fiber.

Abstract: Provided is a method and apparatus for the thermal analysis of a substance. The method comprises suspending a substance sample on a substrate in a reactor using a temperature sensor positioned at the center of the reactor. The reactor is then heated by two laser beams focused on the reactor. The resulting temperature dependence of the sample/substance during heating is measured. Additionally, the sample/substrate is heated to a temperature above the reactor temperature with a third laser beam. The rate at which the sample/substance temperature relaxes to the temperature of the reactor is measured. This additional heating of the sample/substance is preferably achieved by a laser focused on the sample/substance itself. All of the measured information can then be fed into a computer through an electronic interface to provide data on the particular substance undergoing thermal analysis.

Abstract: A gas sensor of the thermal conductivity type suitable for the quantitative analysis of the fuel vapor content of a fuel-air mixture. The gas sensor (10) comprises a sensing element (28) and a compensating element (30), each of which includes an electrically-heated hot member (38) incorporated into a Wheatstone bridge circuit powered by a constant current supply circuit (70). The constant current supply circuit (70) is adjusted and regulated such that the hot member (38) of the sensing element (28) is heated with an electric current of such an intensity that corresponds to a point of transition (Y) at which, at the interface of the hot member (38) and the mixture, the predominant mode of heat transfer changes from thermal conduction to natural convection.

Abstract: A heating sensor capable of generating heat and measuring its own temperature is placed in a fluid and a thermometric sensor is placed in the fluid and inside a temperature boundary layer formed around the heating sensor upon heat generation therefrom. A temperature of the heating sensor and a temperature of the fluid are measured. A relationship between thermal conductivity of the fluid and a differential value between the temperature of the heating sensor and the temperature of the fluid is used to determine the thermal conductivity of the fluid. Then, the heating value of the heating sensor is adjustably increased so that the thermometric sensor is positioned outside the temperature boundary layer. A temperature of the heating sensor and the temperature of the fluid are measured. The relationship between kinematic viscosity of the fluid and a differential value between the temperature of the heating sensor and the temperature of the fluid is used to determine the kinematic viscosity of the fluid.

Abstract: The scanning thermal probe microscope measures a thermal parameter such as thermal conductivity or temperature of surface contours of a specimen with a thermal sensor maintained in thermal communication with the surface of the specimen and maintained at a temperature different than that of the specimen. The thermal sensor is disposed on the free end of a cantilever arm in thermal communication with the probe. A thermal feedback bridge circuit can maintain the thermal sensor at a constant temperature by heating or cooling the sensor, and provides a signal for determining the heat transfer between the probe and the specimen. The cantilever arm includes first and second legs of electrically conductive material, and the thermal sensor comprises a narrowed portion of the conducting material having a relatively high temperature coefficient of resistance.

Abstract: The present invention relates to analytical methods for determining the composition of a material that undergoes a transition as a function of a driving variable. As applied to thermogravimetric analysis (TGA), a first preferred embodiment comprises (1) decreasing the heating rate when deviations from a baseline signal are detected; (2) establishing a minimum heating rate; (3) forcing the heating rate to a predetermined maximum whenever the rate of change of the weight change with respect to the temperature falls below a predetermined value; and (4) adjusting the heating rate according to the rate of change of the weight of the sample to track a predetermined rate of change of the weight of the sample.

Abstract: A heating sensor is disposed within a pipe with a clearance between an inner wall of the pipe and an outer surface of the heating sensor such that a measurement of thermal conductivity is free from any influence of a convective heat transfer. Temperatures of the fluid and the heating sensor are measured and a differential temperature therebetween in steady state heating is determined. A correlation is established between the differential temperature and a thermal conductivity of the fluid and is utilized to obtain the thermal conductivity of this fluid.

Abstract: Disclosed herein is a measuring apparatus and a measuring method which can measure a physical property value such as an oxygen content or thermal conductivity of a sample material such as an aluminum nitride sintered body with high accuracy, over the entire material in a short time. A microwave oscillation source generates microwaves. A sample material to be evaluated, such as an aluminum nitride sintered body, is placed in a cavity resonator, irradiated with microwaves (M), and subjected to a magnetic field (H) applied by electromagnets. An amount of microwaves absorbed by the object is measured by a microwave absorption measuring unit. This amount of microwave absorption is obtained from an electron spin resonance spectrum. The concentration of unpaired electrons in the object is obtained from the measured amount of microwave absorption on the basis of a known relation between an amount of microwave absorption and concentration of unpaired electrons.

Abstract: A method and apparatus for measuring the thermal conductivity of materials using modulated differential scanning calorimetry (MDSC). Two MDSC heat capacity measurements are made consecutively. One measurement is made under conditions which ensure obtaining a fairly accurate value for the heat capacity of the material ("quasi-ideal conditions"). Another measurement is made under conditions such that the measured effective heat capacity differs from the accurate value of the heat capacity due to thermal conductivity effects. Generally, the non-ideal conditions differ from the ideal conditions by one parameter, such as the size of the sample, the modulation frequency used to measure the heat capacity, or, for thin films, the presence or absence of a specimen on the thin film. The thermal conductivity of the material is then calculated from the difference between the heat capacity measured under quasi-ideal conditions and the effective heat capacity measured under non-ideal conditions.

Abstract: A combustionless measurement method and apparatus are described for ascertaining the quality and/or quantity of gaseous fuels fed to gas consumption devices, and particularly natural gas consumption devices. The technique utilizes a novel empirical algorithm for correlating easily measured gas parameters to any one of the: heating value of the fuel gas; density of the fuel gas; and percent concentration of inert gases within the fuel gas. Sensed fuel gas parameters can include any combination of viscosity, thermal conductivity, specific heat, and optical absorption, etc., at more than one temperature if needed for accuracy. Specific structures are set forth for implementing the technique.

Abstract: A thermal test apparatus for measuring the thermal heat transfer characteristics of semiconductor packaging material as well as the thermal characteristics of the package design is disclosed comprising a substrate having the size and shape of a semiconductor die. The substrate is in contact with the semiconductor packaging material. A heating source for heating the substrate is located within the apparatus, along with a temperature sensitive element for which the voltage drop across the element is a function of temperature. The element is connected in series via a first set of conductive traces to forcing pads used to force current through the element. Sensing pads for measuring the forward voltage drop of the diode are connected in parallel via a second set of conductive traces across the element to two points very close to the element in order to greatly reduce the thermal resistance measurement error due to the resistance in the conductive trace material.

Abstract: In order to measure the in-plane thermal conductivity of a sample plate, the plate is placed in a prefabricated device containing (1) a pair of thermocouples, (2) a source of heat flow into the plate, (3) a heat sink of the heat flow having an open cavity, (4) a taut membrane, on which the source of heat flow and the thermocouples are bonded, located on the resilient filling, (5) a resilient filling of thermally insulating material located underneath the membrane, in the cavity of the heat sink, and (6) a thermally insulating medium covering the plate and exerting a compressive force on it.

Abstract: A method and/or an apparatus for the determination of whether a subject has nerve damage (polyneuropathy) and/or the degree of the nerve damage is characterized in that an increase of the skin temperature is provoked at an extremity of the subject, that at the same time perfusion value or a value correlated with this perfusion value is measured at this extremity, and the time from the start of the increase in temperature of the skin up to the start of an increase in perfusion as a result of the elevated skin temperature is evaluated as a measure for the presence and/or the degree of the nerve damage.

Abstract: The present invention provides a method for measuring thermal conductivity of a material at a stationary state at an elevated temperature T.

Abstract: This invention provides a sensing system for measuring a specific value such as the thickness, thermal conductivity, or the like of a substance to be measured by utilizing a change in thermal resistance with a simple arrangement. A sensor has a temperature difference setting thin film (202) and a temperature difference detection thin film (203) formed on a substrate (201) made of a thermally poor conductor, converts a change in temperature difference of the substrate (201) before and after a substance (200) to be measured is thermally coupled to the substrate into a change in thermal resistance of the substrate (201), and outputs the change in thermal resistance as a temperature difference information signal for calculating a desired specific value of the substance to be measured.

Abstract: A method for correcting the flow measurement of a gaseous or liquid fluid of interest for changes in the composition and temperature of that fluid in a flowmeter of the hot element type is disclosed in which an uncorrected flow value signal for the fluid of interest in relation to a hot element sensor output is corrected by applying a first correction factor to the output based on certain unique physical parameters of the fluid of interest which nominally include thermal conductivity, k, specific heat, c.sub.p, and temperature, T, obtaining an uncorrected flow measurement value from the corrected output and obtaining the corrected flow measurement by applying a second correction factor to the uncorrected flow measurement value based on the certain unique physical parameters.

Abstract: A method for modeling a conducting material sample or structure system, as an electrical network of resistances in which each resistance of the network is representative of a specific physical region of the system. The method encompasses measuring a resistance between two external leads and using this measurement in a series of equations describing the network to solve for the network resistances for a specified region and temperature. A calibration system is then developed using the calculated resistances at specified temperatures. This allows for the translation of the calculated resistances to a region temperature. The method can also be used to detect and quantify structural defects in the system.

Abstract: An apparatus for coagulating treatment which is capable of controlling the amount of addition of a coagulant to the optimum level thereby minimizing the water content of the dehydrated cake comprises coagulant adding devices (6), (7), and (8) for causing the coagulant to be added in a variable amount to a liquid subjected to the coagulating treatment, a heat transfer detecting meter (12) disposed so as to contact the liquid to which the coagulant is to be added, the liquid to which the coagulant has been added, or the filtrate from the liquid to which the coagulant has been added and adapted to detect a feeble change in the physical property of the liquid in the form of a change in voltage, and a control device (16) for controlling the amount of addition of the coagulant in the coagulant adding device (8) so that the value of detection of the heat transfer detecting meter (12) is minimized or kept within a desired range.

Abstract: A method of determination of gas properties at reference conditions of temperature and pressure. This determination is needed in systems including mass flow meters, combustion control systems, gas meters and the like. The system disclosed enables the determination of properties including specific heat and thermal conductivity at reference conditions.

Abstract: A method for detecting changes in the rate of heat transfer through a tube wall due to the deposition or removal of deposits formed thereon. The method involves obtaining a segment of tubing, placing a highly conductive material in contact with one of the inner surface and outer surface of the tubing wall, contacting the other of the inner and outer surface of the tubing wall with a heating or cooling medium, and measuring the time required for the temperature of the thermally conductive material to change between two predetermined temperature measurement points. Subsequently, the wall of the tubing segment is cleaned or the tubing segment is replaced with a different tubing segment, and the rate of temperature change of the tube walls is tested again in a similar manner. By comparing the times measured in the first and second trials, the difference in the rate of heat transfer before and after cleaning of the tubing segment can be determined.

Abstract: There is disclosed a system and method for generating characteristics of a surface using an analysis of the infrared image of the surface. A heat balance equation is generated and a technique is presented for solving the equation to generate the absorptivity and conductivity indices of the surface. These indices are matched against a data base of indices of various surfaces to achieve material identification. An embodiment is disclosed in which the indices are used to predict surface appearance in the infrared image for different points in time.

Abstract: A device for measuring at least one characteristic of a fluid is provided. The device comprises a measuring channel which is designed for conducting fluid flow therethrough and which is defined by a wall and a substrate. An inlet orifice and an outlet orifice are provided for conducting fluid into and out of the measuring channel and at least one sensor is located adjacent the measuring channel for measuring the characteristic of the fluid. The wall has outer portions, which are sealing adhered to the substrate, and upwardly bent portions, which partially define the measuring channel. The outer portions and the upwardly bent portions are of substantially the same thickness. The wall is preferably made of a synthetic resin, glass, ceramic, silicon nitride, silicon monoxide, silicon dioxide, or combination of these materials.

Abstract: The present invention relates to analytical methods for determining the composition of a material that undergoes a transition as a function of a driving variable. As applied to thermogravimetric analysis (TGA), a first preferred embodiment comprises (1) decreasing the heating rate when deviations from a baseline signal are detected; (2) establishing a minimum heating rate; (3) forcing the heating rate to a predetermined maximum whenever the rate of change of the weight change with respect to the temperature falls below a predetermined value; and (4) adjusting the heating rate according to the rate of change of the weight of the sample to track a predetermined rate of change of the weight of the sample.

Abstract: A method for modeling a conducting material sample or structure (herein called a system) as at least two regions which comprise an electrical network of resistances, for measuring electric resistance between at least two selected pairs of external leads attached to the surface of the system, wherein at least one external lead is attached to the surface of each of the regions, and, using basic circuit theory, for translating measured resistances into temperatures or thermophysical properties in corresponding regions of the system.

Abstract: A method and apparatus measures thermal conductivity of a material effected by measuring a change in the temperature of the material in contact with a heat source maintained at a predetermined temperature. A temperature change characteristic is obtained from the result of the temperature measurement, and the thermal conductivity is obtained by comparison of the temperature change characteristic and unsteady heat transfer characteristics of solid bodies previously determined in consideration of the heat transfer resistance of the interfaces. The present invention is suitable for the measurement of extensive materials, metallic materials to heat insulating materials, specifically suitable for the measurement of materials of high thermal conductivity and heterogeneous or anisotropic and is capable of accurately measuring the thermal conductivity without any special consideration on the interface heat transfer resistance at the measurement stage.

Abstract: The invention is a method for determining the thermal conductivity of an unknown material using a differential scanning calorimeter. Experiments conducted in a non-adiabatic environment govern the mathematics of the present method. Multiple samples of the unknown material are formed with different lengths and identical cross-sectional areas. Samples of a reference material, having a known thermal conductivity and a density approaching that of the unknown sample, are formed with the same lengths and cross-sectional area as the unknown samples. Each sample is subjected to the same heat rise in a differential scanning calorimeter to determine values of Q heat flow at selected incremental temperatures. A heat equation for the reference sample and the unknown sample is formed and solved for each like length and temperature value of a reference and sample material to determine the thermal conductivity of the unknown sample.

Abstract: The thermal time constant of fine metal wire segments, such as those used to initiate explosive reactions, is measured by passing a variable frequency source of current through the wire. The magnitudes of the sine and cosine components of the third harmonic of the voltage developed across the wire are detected and compared to each other to provide a control signal which is applied to the frequency source to change the its frequency in a direction which tends to make those components equal in magnitude. The magnitude of the control signal, when the third harmonic sine and cosine components are equal, is displayed as a function of the thermal time constant of the wire segment.

Abstract: A device for measuring thermal properties of a test substance, which device incorporates a thin element or a layer of an electrically conductive material, e.g. metal, intended to be brought in heat conductive contact with said test substance (3), means for passing an electric current through said element or layer for supplying heat to the test substance and causing a temperature increase therein and instrument for recording the voltage variation over the element or layer as a function of time. In order to increase the characteristic time for the experiments and thereby making it possible to use less sophisticated measuring instruments the active part of said element (6) or layer (4) over which the measurement is made has substantially equal size along at least two lateral dimensions. The element can e.g. be given of square or circular shape.

Abstract: The disclosure involves a method for calibrating a system for determining thermal conductivity, k, and specific heat, c.sub.p of a fluid of interest. A proximately positioned heater and sensor are in thermal communication through a fluid of interest, and determinations are based on transient and steady-state temperature responses of the sensor to energy input in the heater. Calibration of the precise relations for each such system are determined by derivation using species of known physical property values.

Abstract: A constant power thermal property sensor compensates for changes in the temperature of the medium into which the sensor is disposed. The sensor has two side-by-side probes mounted in the medium with resistances that vary with temperature. A constant power source produces a current through the first probe and a current source applies a current to the second probe at a fixed ratio of the current in the first probe. The voltages across the probes are monitored and compared, and a signal is produced which is divided by current through the first probe. The resulting signal is representative of the heat transfer between the probes and the medium. The signal does not appreciably vary with changes in the temperature of the medium, and the medium may be a liquid, a gas, a liquid flow, a gas flow, or a combination of media. In this construction, two principal applications for the sensor are liquid level detectors and flow monitors.

Abstract: A pyroelectric calorimeter including a detector having a support member with a tapered through-hole therein, a first polyester film positioned on said support member, across said through-hole, an aluminum foil member located on an opposite side of said polyester film from said support member, a pyroelectric film located on an opposite side of said aluminum foil member from said first polyester film, at least one additional polyester film located on an opposite side of said pyroelectric film from said aluminum foil member, two pyroelectrical leads connected to opposite sides of said pyroelectric film, a support for the detector and electrical circuitry for receiving a signal produced from the detector and for generating an output signal therefrom.

Abstract: A brake fluid tester for measuring the quality of brake fluid, comprising means for measuring the conductivity of the brake fluid, preferably comprising a plurality of comparators for comparing the resistance of the brake fluid to a plurality of reference, resistances. The device further comprises indicating means, preferably light emitting diodes, responsive to the measuring means for indicating the quality of the brake fluid based upon its measured conductivity. An increasing number of diodes are illuminated as the conductivity of the brake fluid increases, providing a positive indication when the device is working and providing an easy to interpret display of the test results. The diodes are preferably activated at preselected levels of conductivity, corresponding to preselected levels of moisture contamination.

Abstract: A system for measuring the thermal characteristic of the surface-lattice of solid state materials with picosecond time resolution uses a picosecond laser pulse which is synchronized with a picosecond electron pulse; the electron pulse being generated by splitting the laser pulse into two beams one of which interacts with the surface under test and the second activates the cathode of an electron gun creating an electron pulse which is, collimated, focused and incident at a small acute angle (1-3 degrees) on the surface. The electron pulse generates a reflection high energy electron diffraction pattern (RHEED) which provides information on the surface temperature in accordance with the Debye-Waller effect. Time resolved measurements are made by using electron pulses which are delayed with respect to the laser pulses by successively greater time intervals.

Abstract: A method for determination of the thermal conduction coefficient of a material sample comprises measurement of momentary temperature differences between two opposite surfaces of the material sample and measurement of heat supplied by a heater. Said material sample is placed in a system composed of the heater, two identical reference samples having known thermal conduction coefficient and two heat sinks. The material sample and the heater are sandwiched between the two heat sinks. All of them as so arranged are maintained in thermal contacts with each other. The measurements are made during a continuous linear change of the temperature of the two heat sinks.

Abstract: A method for measuring a heat transfer coefficient between a heat transfer element and a fluid comprising a measurement of a calorific value by placing the heat transfer element into the fluid and charing the heat transfer element with electricity. A calorific value of a particular surface of the heat transfer element is the true calorific value of the entire heat transfer element, since the particular surface of the heat transfer element is thermally insulated from a residual surface of the heat transfer element so as to prevent a heat transfer of the residual surface of the heat transfer element.

Abstract: Apparatus for testing material for thermally insulating pipes comprises a closed loop of pipe in a square configuration with an electric heater mounted coaxially within it. Thermocouples are attached to the pipe from the inside, and they and the heater are accessible via removable caps at the corners of the square. The pipe is suspended from a support framework by rods of low thermal conductivity welded to the inside corners of the square. The insulating material is applied to the pipe, and additional thermocouples fixed to its exterior. The heater is energized and the steady-state temperatures inside and outside the insulating material are measured. The configuration of the apparatus enables corrections for non-uniformity of heat loss and leakage through the rods to be readily made. Thus thermal conductivity values accurately representative of the performance of the insulating material in actual operation can be derived from the temperature measurements.

Abstract: A method and apparatus for determining both the thermal conductivity, k, and specific heat, c.sub.p, of a fluid of interest are disclosed. An embodiment uses proximately positioned resistive heater and thermal sensor coupled by the fluid of interest. A pulse of electrical energy is applied to the heater of a level and duration such that both a transient change and a substantially steady-state temperature occur in the sensor. The k of the fluid of interest is determined based upon a known relation between the sensor output and k at steady-state sensor temperature; and c.sub.p of the fluid of interest is determined based on a known relation among k, the rate of change of the sensor output during a transient temperature change in the sensor and c.sub.p.

Abstract: A process for the simultaneous, in-situ determination of thermophysical properties, primarily for determination of the thermal conductivity and thermal diffusivity, according to which in a certain volume of the material to be tested a temperature field varying with time is brought about by perturbation due to heating and this temperature field is measured, then certain properties are determined by calculation from the obtained temperature data and the known heating power input spherical isotherms are formed in the material to be tested in a way, that temperature change of at least one degree Celsius is brought about at the measuring points which are arranged along a straight line passing through the heat source and intersecting the isotherms along their diameter, and a measuring probe formed as a rod-type body made of poor heat conductive material having a heating element and measuring points, wherein the heating element is formed as a point-like heat source.

Abstract: There is provided by the present invention an apparatus for measuring thermal conductivity. The apparatus is mainly composed of (a) a container adiabatically enclosing an inner space, (b) a heat source for heating a first surface of a specimen to be placed to divide the inner surface into a first space and a second space; (c) a first thermometer to measure the temperature of the first surface of the specimen; (d) a heat-flow-measuring means disposed in contact with the second surface of the specimen, for maintaining the temperature of the second surface of the specimen at a predetermined temperature and for measuring the thermal energy flowing through the second surface; and (e) a second thermometer for measuring the temperature of the second surface of the specimen.

Abstract: A sequence of temporally-spaced radiant energy pulses are applied to the front surface of the sample and the heat rise caused by each thermal pulse is measured at the second surface using a suitable thermocouple or infrared sensor. The temperature rise data for each pulse is digitized and stored in a two-state memory device such as a random access memory. The data from each successive pulse is coadded and statistically processed by averaging to derive a set of favored values indicative of the temperature of the sample as a function of time. The favored values data is further processed using a least squares curve fitting algorithm to determine a numerical value indicative of the diffusivity of the sample.

Abstract: The thermal conductivity in a gas blend is measured in order to determine concentration using several different temperatures for the gas but the same sensor, which includes a Silicon carrier of a few hundred micrometers thick and being provided with an electrically insulating layer; carrying a sputtered on or vapor deposited, meandershaped thin film resistance; a pit in the carrier underneath the resistance and the insulating layer, there being one or more perforations in the insulation to permit access of gas to the interior of the pit; a cover plate made also of silicon and of comparable thickness dimensions as the carrier, and also having a pit of comparable dimensions as the first mentioned pit is disposed above the carrier so that said pits are aligned and constitute a common measuring chamber; and a diffusion channel in the cover plate for feeding a gas through diffusion so that the measuring chamber is defined by the communicating pits.

Abstract: A method for detecting a state of a substance existing in a pipe, the outer surface of which is exposed, which comprises: heating or cooling a pipe, the outer surface of which is exposed, from the side of the outer surface thereof so that a difference in temperature is produced between a portion of the outer surface of the pipe corresponding to a portion of the inner surface thereof, which is in contact with a solid or liquid substance existing in the pipe, and a portion of the outer surface of the pipe corresponding to a portion of the inner surface thereof, which is not in contact with the substance; then shooting the outer surface of the pipe by means of a thermal imaging system while the above-mentioned difference in temperature still remains on the outer surface of the pipe to obtain a thermal image of the difference in temperature; and detecting a state of the substance existing in the pipe by means of the thus obtained thermal image.

Abstract: A method and an apparatus for detecting a defective portion on the inner surface of a pipe, the outer surface of which is exposed, includes: heating or cooling a pipe, the outer surface of which is exposed, from the side of the outer surface thereof so that a difference in temperature is produced between a portion of the outer surface of the pipe corresponding to an accumulation of foreign matters or a thinner portion as a defective portion on the inner surface thereof, and a portion of the outer surface of the pipe corresponding to a normal portion of the inner surface thereof; then shooting the outer surface of the pipe by means of a thermal imaging system while the above-mentioned difference in temperature still remains on the outer surface of the pipe to obtain a thermal image of the difference in temperature; and detecting the accumulation of foreign matters or the thinner portion as the defective portion of the inner surface of the pipe by means of the thus obtained thermal image.

Abstract: An apparatus and method for measurement of the thermal conductivity of polymer melts is disclosed. A sample of material to be measured is placed in an elongated cylindrical container and is heated to a preselected base temperature. A probe placed in the container in contact with the sample contains a transient heating element and a temperature sensor. To determine the thermal conductivity of the sample material, the transient heating element is energized and the resulting changing temperature of the sample material is measured for a short period of time. The rate of temperature change is a measure of the thermal conductivity of the sample material at the base temperature.

Abstract: Thermal conductivity, thermal diffusivity and/or fluid perfusion within a medium such as cutaneous tissue is non-invasively measured by at least two heating and temperature sensor. One sensor is positioned in thermal communication with the medium and a second sensor is positioned thermal communication with the first sensor. Both sensor are heated (or cooled) so as to substantially prevent net heat flow between them. In this manner, net heat flow between the first sensor and the medium can be measured, which measurements allow determination of the thermal conductivity, thermal diffusivity and/or fluid perfusion within the medium.

Abstract: A method for determining the properties of a medium by activating temperature changing means to change the temperature of the medium from a first unperturbed temperature to a second different temperature during a first time period and permitting the temperature to relax to a final unperturbed temperature during a second time period. In a particular embodiment, for example, the intrinsic thermal conductivity and diffusivity of the medium are calculated during a selected portion of the first time period assuming an arbitrary value for the perfusion, and the perfusion of the medium is calculated during a selected portion of the second time period using the calculated intrinsic thermal conductivity and diffusivity. The calculated perfusion is then used to recalculate the intrinsic thermal conductivity and diffusivity during the selected portion of the first time period and the perfusion is then recalculated using such recalculated intrinsic thermal conductivity and diffusivity.

Abstract: Apparatus for measuring the thermal conductivity of a gas has first and second, heatable and temperature-dependent measuring resistors in sufficiently close, tandem proximity along a flow path for the gas and connected in opposite arms of a measuring bridge circuit.

Abstract: This invention relates to the measurement of thermal conductivity. The measuring probe according to the invention is characterized in that it comprises:a plate defining, on its face of application, areas located on the same plane, occupied by the measurement zones (Z.sub.1, Z.sub.2) which are constituted by conducting segments connected in series from one zone to the other by thermocouples,a plane heating element placed, outside the face of application, in relation with the median zone Z.sub.1,a coating made of electrically insulating matter, covering the measurement zones Z.sub.1, Z.sub.2,a cover made of insulating matter covering the plate,and a mass (M) of heat-insulating matter occupying the volume defined by the plate and the cover. The invention is more particularly applicable to the study of the thermal conductivity of biological tissues.

Abstract: A method for determining the thermal characteristics of a semiconductor packaging system is provided which uses a platinum resistor test unit. The platinum resistor is preferably sized to approximate the dimensions of the semiconductor device for which the package was designed, and is installed within the package. The packaged resistor is then thermally calibrated at a plurality of temperature levels to generate a linear temperature versus resistance graph or equation corresponding thereto. Next, voltage is applied to the packaged resistor causing such resistor to "self heat." Its resistance is calculated, and the temperature corresponding thereto is obtained from the graph or equation. Such temperature is the surface temperature of the resistor. This temperature may then be used to calculate the temperature gradient from the inside of the package to any reference point on or near the outside of the package, the temperature of which has been previously determined.

Abstract: A novel test die for emulating the thermal characteristics of functional product dies includes a plurality of concentric emulator ring configurations fabricated about the die center, each having a plurality of heating resistors approximately forming a rectangle, a plurality of sense diodes located in proximity to the heating resistors and a plurality of hot spot resistors located in proximity to both the heating resistors and the sense diodes. Metallic interconnections are formed on the die which selectively provide each of the heating resistors and hot spot resistors with excitation signals and present signals from the sense diodes indicative of the voltage thereacross.