R.M. Young 05106 Wind Monitor

The 05106 is the marine version of R.M. Young's Wind Monitor, and the Wind Monitor is probably the most widely deployed propeller-vane anemometer in professional meteorology. Its design is old enough to be thoroughly characterised, which is exactly what you want in a reference instrument: the response of this sensor to a gust is published, repeatable and comparable with decades of data taken by the same instrument.

What separates the marine model from the standard 05103 is corrosion. YOUNG describe it as similar in operation but using long-lasting, corrosion resistant ceramic bearings and ruggedised vertical components for the additional rigors of the marine environment. Bearings are the whole argument. A propeller anemometer's accuracy at low wind speed depends entirely on how freely its bearings turn, and salt air degrades ordinary bearings until the sensor stops responding to light winds - reporting calm when there is a breeze, which is the failure mode least likely to be noticed and most likely to matter.

The published figures are a range of 0 to 100 m/s - 224 mph, well beyond any wind that will be survived by the structure it is mounted on - with accuracy of 0.3 m/s or 1 percent of reading, and direction to 3 degrees over 360 degrees mechanical and 355 degrees electrical with a 5 degree open sector. Starting thresholds are 1.0 m/s for both propeller and vane. The dynamic response figures are the ones a serious user cares about: a propeller distance constant of 2.7 m for 63 percent recovery, a vane delay distance of 1.3 m for 50 percent recovery, a damping ratio of 0.3 and a damped natural wavelength of 7.4 m. Those numbers describe how faithfully the sensor follows a changing wind, which is what determines whether a reported gust is real.

The outputs are deliberately simple and robust. Wind speed comes out as an AC sine wave whose frequency is proportional to speed, and direction as the resistance of a precision potentiometer. Neither is a digital protocol that can go out of support, and both can be read by almost any data logger or helideck monitoring system - which is why this sensor appears in installations of every vintage.

Two practical details. The cable is attached inside a sealed capsule internal to the sensor, with different lengths available, which removes the exposed connector that is usually the first thing to corrode on a masthead instrument. And it mounts on standard 1-inch IPS pipe, so the mechanical installation needs no proprietary hardware. Orientation at installation matters - direction is meaningless if the sensor is not aligned - and YOUNG supply a mounting orientation ring for the purpose.