A circuit that produces an output signal having a frequency that is proportional to absolute temperature (PTAT) is disclosed. In one embodiment, the circuit includes a ring oscillator and a bias current circuit coupled thereto. The ring oscillator and the bias current circuit are implemented in close proximity to one another. During operation, the bias current circuit generates a bias current that is provided to the ring oscillator. The amount of bias current generated is dependent upon the temperature of the circuit. In turn, the frequency of an output signal provided by the ring oscillator is dependent on the amount of bias current received from the bias current circuit. Accordingly, the frequency of the ring oscillator output signal is dependent on the temperature of the circuit.

A temperature probe and method for determining a temperature in a gas flow are disclosed. The probe includes a probe body. A free flow temperature sensor a free flow temperature of the gas flow and a total temperature sensor measures a total temperature of the gas flow. The method includes measuring a flow temperature in a free gas flow, providing a static gas volume in which essentially all kinetic energy of the flowing gas is recovered and converted into thermal energy, and measuring a total temperature in the static gas volume. An accurate determination of the total temperature of a gas flow, which is representative of a specific total enthalpy, can thereby be achieved while detecting fast and transient temperature changes.

A sensor includes a mount arranged along a sensor axis, an airfoil body fixed to the mount and having a first face and second face extending along the sensor axis, a heater element, and a temperature probe. The heater element and the temperature probe are positioned within the airfoil body and extend axially along the airfoil body. The airfoil body defines within its interior a pressure channel having an inlet segment extending between the heater element and the first face of the airfoil body to prevent ice formation and/or melt ice entrained within air traversing the pressure channel. Gas turbine engines, methods of removing ice or preventing ice formation, and methods of making sensors are also described.

A system and method for calculating aircraft total air temperature from bypass flow temperature in a turbofan gas turbine engine having a bypass flow duct includes sensing aircraft speed (M), sensing engine fan speed (N.sub.1), sensing core engine speed (N.sub.2), and sensing bypass air flow temperature (T.sub.15) in the bypass flow duct. Total air temperature (TAT) is calculated as a function of the sensed aircraft speed, the sensed engine fan speed, the sensed core engine speed, and the sensed bypass air flow temperature. In some embodiments, fan bleed airflow is determined, and a correction is applied to the sensed bypass airflow temperature, and aircraft total air temperature (TAT) is further based on the corrected bypass airflow temperature.

Embodiments of icing resistant total temperature probes with integrated ejectors are provided. One air data probe comprises: a base; a body having a leading and trailing edges: a first passage defining a first annulus; a temperature sensor within the first passage; a heat shield defining an exterior wall of at least part of the first passage, wherein the sensor is positioned within the shield; a second passage comprising a second annulus defined by a space between the shield and the body; an intake port having an intake aperture that opens to the first and second passages; a separate heated airflow passage, the heated airflow passage having an air input port configured to couple to an air supply source and following a path within the probe body; an integrated air ejector coupled to heated airflow passage to motivate air into the intake aperture and through the first and second air passages.

A total air temperature (TAT) probe having a self-regulating heating system is provided. A TAT probe housing includes at least one heating cavity that is located proximate to a tip of the TAT probe. A heating element is received within the at least one heating cavity. The heating element is composed from a flexible material with a very high positive temperature coefficient (PTC) that provides non-linear resistance with temperature with generally relatively low electrical resistances at temperatures below freezing and relatively high electrical resistances above freezing. A power source is coupled to the heating element. The very high PTC material of the heating element causes less power to be drawn by the heating element from the power source at higher temperatures above freezing than the power drawn by the heating element from the power source at lower temperatures below freezing to maintain a desired temperature of the TAT probe.

An air data probe includes a probe body including a probe wall. The probe body is formed from a first material by direct energy metal deposition. An insert is positioned in the probe wall. The insert is formed from a second material different from the first material. The insert is encapsulated in the probe wall via the direct energy metal deposition. A method of forming an air data probe includes forming one or more thermally conductive inserts, and encapsulating the one or more inserts into a wall of an air data probe via direct energy metal deposition. The air data probe is formed from a first material and the one or more inserts are formed from a second material different from the first material.

A total air temperature probe includes a housing defining a total air temperature sensor flow passage and a sensor assembly positioned within the total air temperature sensor flow passage. The sensor assembly includes an element flow tube, and a sensing element within the element flow tube. An upper portion of the element flow tube is an entrance including a plurality of protrusions that extend in an upstream direction.

Systems and methods for icing resistant total air temperature probes are provided. In one embodiment, a total air temperature data probe comprises: a probe base; a probe body comprising: a first interior airflow passage comprising a first annulus; a temperature sensor positioned within the first annulus; a heating element; a notched intake port positioned at a distal end, wherein the probe body provides a conductive thermal path from the heating element to the intake port, the intake port including an open channel extending inward into an intake aperture of the probe body, and a cutaway region that defines a recessed second face inset from the first face and exposes the open channel at least partially from the leading edge. The notched intake port further comprises a slot inset from the recessed second face that traverses across at least a portion of the intake aperture perpendicularly to the open channel.

A handheld apparatus for measuring atmospheric temperature inversions consisting of a battery powered electronic display portion, a folding pole portion, and a temperature sensor protected from sources of heat radiation. An electronic circuit measures air temperatures at multiple heights accurately by automatically determining when readings have stabilized and reads a tilt sensor to assure temperature readings are at the proper height. Affixing said temperature sensor to the end of a pole while the opposite end is held in the user's hand facilitates waving of the temperature sensor end through the air to increase air flow, therefore, assuring quicker response and accurate air temperature readings. An electronic display indicates the presence and intensity of an atmospheric temperature inversion.