Disclosed is a method and apparatus for measuring semiconductor substrate temperature using a differential acoustic time of flight measurement technique. The measurement is based on measuring the time of flight of acoustic (ultrasonic) waves across the substrate, and calculating a substrate temperature from the measured time of flight and the known temperature dependence of the speed of sound for the substrate material. The differential acoustic time of flight method eliminates most sources of interference and error, for example due to varying coupling between an ultrasonic transducer and the substrate. To further increase the accuracy of the differential acoustic time of flight measurement, a correlation waveform processing algorithm is utilized to obtain a differential acoustic time of flight measurement from two measured ultrasonic waveforms. To facilitate signal recognition and processing, a symmetric Lamb mode may be used as mode of excitation of the substrate.

Disclosed is a method and apparatus for measuring semiconductor substrate temperature using a differential acoustic time of flight measurement technique. The measurement is based on measuring the time of flight of acoustic (ultrasonic) waves across the substrate, and calculating a substrate temperature from the measured time of flight and the known temperature dependence of the speed of sound for the substrate material. The differential acoustic time of flight method eliminates most sources of interference and error, for example due to varying coupling between an ultrasonic transducer and the substrate. To further increase the accuracy of the differential acoustic time of flight measurement, a correlation waveform processing algorithm is utilized to obtain a differential acoustic time of flight measurement from two measured ultrasonic waveforms. To facilitate signal recognition and processing, a symmetric Lamb mode may be used as mode of excitation of the substrate.

Under one aspect, a method of processing a material includes heating a region of the material with a first energy source; exciting an acoustic wave in the material; and transmitting the acoustic wave through the heated region, the heated region changing at least one property of the acoustic wave. The method also can include detecting the change in at least one property of the acoustic wave; characterizing a temperature of the material in the heated region based on the detected change in at least one property of the acoustic wave; and comparing the characterized temperature of the material in the heated region to a threshold. The method further can include, based on the characterized temperature of the material in the heated region being less than the threshold or being above the threshold for an insufficient amount of time, modifying a property of the heated region with a second energy source.

The disclosure relates to a method for determining a temperature in a pressurized flow path of a gas turbine comprising the steps of sending an acoustic signal from an acoustic signal emitting transducer across a section of the pressurized flow path, detecting the acoustic signal with a receiving transducer, measuring the time needed by the acoustic signal to travel from the acoustic signal emitting transducer to the receiving transducer, calculating the speed of sound, and calculating the temperature as a function of the speed of sound, the heat capacity ratio (□) and a specific gas constant (R.sub.spec) of the gas flowing in the pressurized flow path. Besides the method, a gas turbine with a processor and transducers arranged to carry out such a method is disclosed.

The disclosure relates to a method for determining a temperature in a pressurized flow path of a gas turbine comprising the steps of sending an acoustic signal from an acoustic signal emitting transducer across a section of the pressurized flow path, detecting the acoustic signal with a receiving transducer, measuring the time needed by the acoustic signal to travel from the acoustic signal emitting transducer to the receiving transducer, calculating the speed of sound, and calculating the temperature as a function of the speed of sound, the heat capacity ratio (□) and a specific gas constant (R.sub.spec) of the gas flowing in the pressurized flow path. Besides the method, a gas turbine with a processor and transducers arranged to carry out such a method is disclosed.

According to various, but not necessarily all, embodiments there is provided an apparatus comprising means for: determining a time difference between arrival at a device of a sound produced by a sound source and an electromagnetic signal reflected from a surface, of a body comprising the sound source, which vibrates when the sound is produced; and providing the time difference to enable determination of a fluid temperature based on the speed of sound through the fluid between the body and the device.

The invention discloses methods for simultaneously measuring various properties of a fluid using a waveguide. The method includes transmitting a plurality of wave modes into the fluid using an ultrasonic shear wave transducer from one end of a waveguide. Further, the wave modes are reflected from the other end of the waveguide. The reflected wave modes are processed simultaneously. The time of flight and the amplitude of the received wave modes are determined. Further, one or more properties of the fluid are measured using determined time of flight and amplitude of the received wave modes. The disclosed method is used to accurately measure the properties of fluid such as level, density, viscosity or flow rate in a short period of time.

A method for calibrating a temperature measuring unit based on ultrasound measurement includes: establishing an empirical functional relationship between the medium temperature of a medium to be measured and the velocity of sound of a measurement signal passing through the medium to be measured; capturing at least the velocity of sound of the measurement signal, the temperature measured by means of a temperature sensor, and the time variation of the sensor temperature at at least two measuring points, wherein the at least two measuring points have a different medium temperature; determining the medium temperature from the measured temperature, taking into account the time variation of the sensor temperature, so that at least two pairs of values and exist; running a compensating curve through the pairs of values which corresponds to the empirical functional relationship; and storing the functional relationship.

A method for calibrating a temperature measuring unit based on ultrasound measurement includes: establishing an empirical functional relationship between the medium temperature of a medium to be measured and the velocity of sound of a measurement signal passing through the medium to be measured; capturing at least the velocity of sound of the measurement signal, the temperature measured by means of a temperature sensor, and the time variation of the sensor temperature at at least two measuring points, wherein the at least two measuring points have a different medium temperature; determining the medium temperature from the measured temperature, taking into account the time variation of the sensor temperature, so that at least two pairs of values and exist; running a compensating curve through the pairs of values which corresponds to the empirical functional relationship; and storing the functional relationship.

An integrated temperature sensor comprises a chip package enclosing an integrated circuit and an ultrasonic transceiver which is integrated on top of the integrated circuit. The ultrasonic transceiver comprises a transmitting element which is arranged for emitting ultrasound waves, and a receiving element which is arranged for receiving ultrasound waves. The chip package comprises at least one barrier arranged at a defined position in the chip package. The barrier is designed to at least partly reflect ultrasound waves emitted by the transmitting element towards the receiving element. The integrated circuit comprises an actuator element to actuate the transmitting element to emit ultrasound waves according to a first signal s(t), and a converter element to convert an ultrasound wave, received by the receiving element, into a second signal y(t). Furthermore, a method for producing an integrated temperature sensor and a method for determining a temperature by means of an integrated temperature sensor are presented.