Relative humidity sensor (standard output)
The humidity sensor FAR025xx is based on a capacitive transducer made up hygroscopic polymers. This material modifies its dielectric constant in function of the water steam in the environment (and so in function of the relative humidity). The transducer is inserted inside an electronic circuit giving an electrical signal proportional to relative humidity.
The transducer is mounted on the top of a support made of plastic material so to minimize heat transfer from the base towards the sensing element.
The sensor body is inserted inside a natural ventilation shield made of a pile of wedge - shaped plates drilled in the middle (so to have space for sensor housing). The air circulation is guaranteed by thermodynamic characteristics of the structure. Three plates not drilled are mounted on the top to protect the transducer form direct solar radiation, rain, hail and in general dust or dirt contamination.
The screen is made of polycarbonate added with glass fiber, material with a high resistance to ultraviolet radiation and atmospheric corrosion: this material keeps its properties stable and it doesn't polymerize even if it's been mounted for a long time outdoor. This, combined with its geometry, guarantees that the shield doesn't affect the sensor response time, important to reach the thermal equilibrium.
The sensor body is made in anticorodal aluminum, a material which guarantees a substantial durability and high resistance to corrosion. To reduce the influence of solar radiation the sensor body is white painted.
On the bottom end of the sensor there is a connector for the signal and supply cable. The connector is watertight and has a screw connection.
For the calibration of the sensor, a certified instrument is used (reference ACCREDIA). The calibration based on comparison allows to maintain continuity with the metrological chain and assigns a scientific value to the measurement.
Forced ventilated radiation shield (option)
The shelter is made by combining different cylindrical parts in order to obtain a cavity where it is possible to house the transducer. On the upper side it’s placed a convex plate to protect the probe from the rain or snow. In the lower part, a dedicated disk allows the blocking of the transducer inside the shield with forced ventilation. A fan located under the top plate sucks air from the cavity in which the transducer is housed. The system is powered by 12Vdc and is able to generate an air flow of about 7m/s. The fact that the air is sucked prevents that the thermal energy generated by the fan can influence the transducer. In this way you can get to thermal equilibrium with the environment.