To measure wind speed and direction, the 6501 incorporates the Vaisala WINDCAP® sensor that uses ultrasound to determine horizontal wind speed and direction. The array of three equally spaced transducers on a horizontal plane is a Vaisala specific design, which ensures accurate wind measurement from any horizontal wind direction without blind angles and corrupted readings. Barometric pressure, temperature, and humidity measurements are combined in the PTU module using capacitive measurement for each parameter. It is easy to change the module without any contact with the sensors. Precipitation measurement is based on the Vaisala acoustic RAINCAP® sensor.

The 6539 humidity and temperature probe is designed for reliable outdoor humidity and temperature measurements. The probe is very accurate and has excellent long-term stability and negligible hysteresis.

The humidity and temperature probe’s small diameter allows it to be used in applications with space restrictions, for example, shipping containers or between planks in timber drying kilns. It is designed especially for demanding outdoor applications.

The probe has the proven HUMICAP® 180R humidity sensor that has excellent stability and withstands harsh environments, as well as Pt100 RTD temperature sensor. The probe structure is solid and the sensor is protected by default with a sintered Teflon filter, which gives maximum protection against liquid water, dust, and dirt.

The 6539 probe is also a warmed probe which reduces the risk of condensation forming on the head of the probe and with that reduces the chance of measurement data corruption.

The probe can be used in conjunction with the Model 6704A Radiation Gill Screen & Mount in standalone situations