| 摘要 |
An air data sensor device, such as a pitot, total air temperature sensor, etc., includes an elongated probe having a sensor therein for sensing air flow parameters and a strut for positioning the probe in a desired position on an air vehicle. To avoid ice build-up on the device causing erroneous sensing of air flow parameters a substantially constant wattage electric resistive heater is provided in the probe for deicing. A PTC (positive temperature coefficient) resistive heater is disposed in the support at a location thermally isolated from the probe heater but in thermally conductive relationship to the external surface of the support. The PTC heater is connected in series with the probe heater and continuously varies heater power in response to the rate of heat dissipation at the external surface of the sensor device thereby preventing burn-out of the probe heater and erosion of the probe. A second constant wattage heater connected in parallel with the PTC heater is located within the probe and has a maximum rated power selected to insure that during conditions of minimum heat dissipation of the probe heater sufficient additional heat is supplied to the probe to perform the deicing function without raising the probe to damaging temperatures.
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