Temperature Sensor

A Temperature Sensor is a meteorological instrument used to measure ambient air temperature, and often pavement surface temperature, at an airfield. It is an essential component of aerodrome weather observation systems, providing data for METAR, TAF, and ATC briefings. Temperature data is used for aircraft performance calculations (density altitude, take‑off and landing distances), winter maintenance decisions (anti‑icing, de‑icing, snow removal), and for general weather reporting. The sensor typically uses a platinum resistance thermometer (PRT), thermistor, or thermocouple, and is housed in a radiation shield to protect it from solar radiation and precipitation.

Airfield temperature data exists to support decisions that go well beyond a simple weather report: aircraft performance calculations depend on air density, which shifts with temperature and directly affects how much runway length a takeoff or landing actually requires. In hot conditions, an aircraft can need significantly more runway to become airborne safely, so accurate, continuously updated temperature readings feed directly into the performance margins pilots and dispatchers rely on before every departure.

On the ground-operations side, pavement and ambient temperature readings are what trigger winter maintenance decisions — when to apply anti-icing chemicals, when frost risk becomes real, and when de-icing becomes mandatory before an aircraft can depart safely. Getting this timing right protects against the loss of lift and control that ice or frost contamination on wings and control surfaces can cause.

Installed at airfields as part of the meteorological observation system, typically at a height of 1.5 to 2 metres above ground level, in a well‑ventilated location away from buildings and heat sources. Temperature sensors are used for weather reporting, ATC information, and input to automated systems such as RVR and weather displays. Pavement temperature sensors are embedded in the runway or taxiway surface to provide data for winter maintenance and friction assessment. They are also used at heliports, remote airstrips, and offshore platforms where temperature data is essential for safe operations.

Air temperature sensors are mounted inside a ventilated radiation shield on a mast or stand, sited over natural ground cover in an open area away from buildings, pavement, and other heat sources, at the standard meteorological height of 1.5–2 m above ground level. Pavement (surface) temperature sensors are instead embedded flush into the runway or taxiway structure during construction or resurfacing, wired in armoured cable run through duct to the roadside cabinet, with the sensing face set level with the surrounding surface so it doesn't disturb aircraft tyre contact or snow-clearing equipment. In both cases, cabling runs underground back to the meteorological equipment shelter or AWOS cabinet, and siting keeps the sensor clear of sprinkler and de-icing spray and vehicle exhaust paths that could bias readings.

An air temperature sensor uses a sensing element (e.g., a platinum resistance thermometer) whose electrical resistance changes predictably with temperature. The sensor is connected to a data logger or weather processor that measures the resistance and converts it to a temperature reading (in °C, °F, or K). The sensor is housed in a radiation shield (often a louvred, passive or fan‑aspirated shield) to minimise the effects of solar heating and to allow free airflow. Pavement temperature sensors are typically embedded in the surface and use similar sensing technology, but are designed to withstand heavy loads and environmental exposure. The output signal is typically 4–20 mA, 0–10 V, or digital (RS‑232, RS‑485, SDI‑12).

The data logger's job doesn't stop at converting resistance to a temperature reading — the AWOS layer above it applies threshold-based alarm logic that turns a raw number into an operational decision. Pavement temperature is continuously compared against the current dew point: when the gap narrows to within a defined margin, the system raises a frost-risk alert to the winter maintenance team well before ice actually forms, rather than waiting for a human observer to notice. Similarly, a sustained pavement or air temperature drop toward freezing triggers a de-icing/anti-icing readiness alert distinct from the routine METAR/TAF reporting cycle. This threshold layer runs independently of, and faster than, the standard reporting interval, because a winter-ops decision can't wait for the next scheduled weather bulletin. The sensor's own health — resistance drift, open-circuit, or out-of-range readings — is checked continuously and reported as a separate maintenance fault, so a failing sensor triggers a service call rather than silently feeding a bad reading into the frost-alert logic.

Air and pavement sensors use the same sensing principle — a Pt100 or thermistor whose resistance changes predictably with temperature — and differ mainly in packaging: a ventilated radiation shield versus a surface-rated housing built to take wheel loads. Both feed the same data logger, which is really the fork point: one reading, converted once, is what METAR/TAF reporting, winter maintenance calls, and RVR/weather displays all read from.

A temperature sensor is built around a platinum resistance thermometer, thermistor, or thermocouple element housed in a radiation shield — typically a louvred, naturally or fan-aspirated white plastic or aluminium enclosure — that protects the sensing element from direct solar radiation and precipitation while allowing free airflow so the reading reflects true ambient air temperature rather than the shield's own surface temperature. The shield and sensor assembly mount on a fixed pole or bracket at the standard reference height above ground, with the sensing element itself sealed in a small stainless-steel or corrosion-resistant probe housing rated to IP65/IP66. Where pavement temperature is also measured, a separate flush-mounted or surface-contact probe is embedded in or bonded to the pavement surface, wired back to the same signal processing unit as the air temperature sensor. Cabling from the sensing element to the transmitter or data logger is shielded and weather-rated, and the enclosure housing the electronics is sealed against moisture ingress, since the sensor is typically sited in an open, unobstructed location with full exposure to wind, rain, and temperature extremes.