A sensor with a mechanical waveguide may be characterized using test ultrasonic signals to generate a baseline signature, and the baseline signature may later be used to detect faults in the sensor.

Methods, apparatus, systems, and articles of manufacture are disclosed to monitor thermal degradation of a compute device. One such method includes calculating, by executing instructions with processor circuitry, a thermal degradation value based on an equation, the equation generated based on testing of thermal interface materials having varying degrees of degradation. The method also includes comparing, by executing instructions with the processor circuitry, the thermal degradation value to a thermal degradation threshold to determine whether the thermal degradation threshold is satisfied, and, when the thermal degradation threshold is satisfied, triggering generation of a thermal degradation alert.

A system for measuring a number of layers in a layered environment includes an ultrasound transducer positioned at an exterior surface of a first layer at a first location. At least one receiving sensor is positioned perpendicular to the exterior surface of the first layer at a second location. The ultrasound transducer and the at least one receiving sensor are in communication with a computer processor, power source, and computer-readable memory. The ultrasound transducer is configured to emit a first ultrasound signal into the first layer at the first location. The at least one receiving sensor is configured to receive a plurality of propagated ultrasound signals. The processor is configured to determine a total number of layers in the layered environment based on at least one from the set of: a number of signals received and a number of propagation direction changes only of the first ultrasound signal.

A system for measuring a number of layers in a layered environment includes an ultrasound transducer positioned at an exterior surface of a first layer at a first location. At least one receiving sensor is positioned perpendicular to the exterior surface of the first layer at a second location. The ultrasound transducer and the at least one receiving sensor are in communication with a computer processor, power source, and computer-readable memory. The ultrasound transducer is configured to emit a first ultrasound signal into the first layer at the first location. The at least one receiving sensor is configured to receive a plurality of propagated ultrasound signals. The processor is configured to determine a total number of layers in the layered environment based on at least one from the set of: a number of signals received and a number of propagation direction changes only of the first ultrasound signal.

A Doppler device including a transducer and processing circuitry is provided. The transducer transmits underwater ultrasonic wave and receives a reflected wave of the ultrasonic wave. The Doppler device generates a first echo signal from the reflected wave in a first direction making a depression angle θ with a receiving surface of the transducer, generates a second echo signal from the reflected wave in a second direction making the depression angle θ with the receiving surface, the second direction being different from the first direction, and generates a third echo signal in a third direction perpendicular to the receiving surface. The processing circuitry further calculates a first Doppler frequency of the first echo signal, a second Doppler frequency of the second echo signal, and a third Doppler frequency of the third echo signal. The processing circuitry further calculates the depression angle θ from the first, second and third Doppler frequencies.

A Doppler device including a transducer and processing circuitry is provided. The transducer transmits underwater ultrasonic wave and receives a reflected wave of the ultrasonic wave. The Doppler device generates a first echo signal from the reflected wave in a first direction making a depression angle θ with a receiving surface of the transducer, generates a second echo signal from the reflected wave in a second direction making the depression angle θ with the receiving surface, the second direction being different from the first direction, and generates a third echo signal in a third direction perpendicular to the receiving surface. The processing circuitry further calculates a first Doppler frequency of the first echo signal, a second Doppler frequency of the second echo signal, and a third Doppler frequency of the third echo signal. The processing circuitry further calculates the depression angle θ from the first, second and third Doppler frequencies.

An active mechanical waveguide including an ultrasonically-transmissive material and a plurality of reflection points defined along a length of the waveguide may be driven at multiple resonant frequencies to sense environmental conditions, e.g., using tracking of a phase derivative. In addition, frequency-dependent reflectors may be incorporated into an active mechanical waveguide, and a drive frequency may be selected to render the frequency-dependent reflectors substantially transparent.

An active mechanical waveguide including an ultrasonically-transmissive material and a plurality of reflection points defined along a length of the waveguide may be driven at multiple resonant frequencies to sense environmental conditions, e.g., using tracking of a phase derivative. In addition, frequency-dependent reflectors may be incorporated into an active mechanical waveguide, and a drive frequency may be selected to render the frequency-dependent reflectors substantially transparent.

A brake temperature sensing system for an aircraft including a sensor apparatus and an interrogation apparatus. The sensor apparatus includes a temperature sensor for attachment to a brake disc of an aircraft brake, and a relay for attachment to the brake. The temperature sensor is configured to wirelessly transmit a measurement signal containing information relating to a temperature of the brake disc, responsive to receiving a wireless interrogation signal. The relay is configured to receive an interrogation signal from the interrogation apparatus; wirelessly transmit the interrogation signal to the temperature sensor; receive the wireless measurement signal from the temperature sensor; and transmit the received measurement signal. The interrogation apparatus comprises a controller configured to generate an interrogation signal; and a transceiver configured to transmit the generated interrogation signal to the sensor apparatus; and receive the measurement signal transmitted by the sensor apparatus.

A brake temperature sensing system for an aircraft including a sensor apparatus and an interrogation apparatus. The sensor apparatus includes a temperature sensor for attachment to a brake disc of an aircraft brake, and a relay for attachment to the brake. The temperature sensor is configured to wirelessly transmit a measurement signal containing information relating to a temperature of the brake disc, responsive to receiving a wireless interrogation signal. The relay is configured to receive an interrogation signal from the interrogation apparatus; wirelessly transmit the interrogation signal to the temperature sensor; receive the wireless measurement signal from the temperature sensor; and transmit the received measurement signal. The interrogation apparatus comprises a controller configured to generate an interrogation signal; and a transceiver configured to transmit the generated interrogation signal to the sensor apparatus; and receive the measurement signal transmitted by the sensor apparatus.