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What type of aerospace temperature sensors are there?



Temperature measuring instruments in aircrafts provide instant and precise feedback for monitoring temperature changes in real time.  These sensors can be in both the engine and the cabin of an aircraft. In an engine, temperature sensors measure the temperature of the fuel and hydraulic oils and coolants. The sensors prevent these components from overheating the engine and causing a safety risk.


The cabin temperature sensors are used to monitor the internal temperatures within the aircraft flight deck and cabin. The two most common aerospace temperature sensors are Thermocouples and Resistance Temperature Detectors (RTD). These temperature sensors are very similar but the RTDs are highly accurate whereas the thermocouples can withstand higher, more extreme temperatures.

AMETEK is familiar with the critical performance features and evaluates those critical aspects early in the development program specific to the application for further risk reduction. This is why AMETEK sensors go through extensive testing and are proven in the field. 

 

 Resistance Temperature Detectors

 


RTDs are resistors with a known resistance vs. temperature. The RTD elements most commonly used are either comprised of platinum wire wound around a ceramic core, or a thin film element in which platinum is deposited on ceramic substrates. 
The majority of AMETEK’s sensors for air temperature include the thin film variety of RTD to take advantage of its compact and repeatable package. 

RTDs can be used as temperature sensors for temperatures up to 850°C. The RTD’s time constant – how long it takes for the sensor to respond to a step change in temperature – is dictated by the thermal mass of the sensor in addition to the convection rate of heat transfer.  As such, time response becomes faster with increasing mass flow rate. 

Thermocouples


The principle of thermocouple operation is based on the Seebeck effect, which states that when junctions of two dissimilar metals forming a closed circuit are exposed to different temperatures, a net thermal electromotive force is generated which induces a continuous electrical current. Minimizing the mass of the thermocouple, while increasing the heat transfer coefficient and surface area, reduces time response. The specific heat is a function of the air temperature.

The thermocouple probe minimizes time response by having small thermocouple elements that are supported by a larger mass to survive the harsh turbine environment. The size of the thermocouple probe, including manufacturing the closure at the tip and the positioning of the junction inside the sheath, are tightly controlled to minimize any variation in time response.

AMETEK has been repeatedly informed by airlines that its EGT thermocouples are preferred over competitors’ sensors because of the noticeable accuracy difference.

Improved accuracy results in the benefit of a greater EGT margin, thus postponing costly engine overhaul shop visits..

Learn more about our temperature sensors here: https://www.ameteksfms.com/products/temperature-sensors



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