Meteorological Office hand anemometer with three cups, unknown maker, 1997. Stamped on reverse: type 1438, serial no. 552429. Labelled with Met Office reference 23510.

Hand anemometers are portable devices used to measure wind speed at the level of the observer. Three cups are mounted on vertical spindle to which is also attached a permanent magnet. An aluminium cup mounted on a pivot, below and concentric with the spindle, carries a pointer. When the cup wheel rotates in the wind, the rotating magnet induces eddy currents in the aluminium cup which tries to turn in the same direction as the magnet against a restraining hair spring. The angular movement of the aluminium cup and the pointer gives a measure of the wind speed.

To use the instrument, the observer holds the anemometer at arms length with its axis vertical, with their arm at right angles to the wind direction to minimise interference from their body.

Fitted wooden case for Meteorological Office hand anemometer, unknown maker, 1997. RAF equipment label attached indicating instrument earmarked for repair, and marked with stamp of the Met Office Calibration Laboratory 4 Nov 1997. ‘Nature of unserviceability: reads erratic at 50 & 60 knots’. Label taped to top of case: ‘TMEC. RAF. St Maurgen RU 27237/3. Anemometer hand. Met 23510 Qty 1’

Hand anemometers are portable devices used to measure wind speed at the level of the observer. Three cups are mounted on vertical spindle to which is also attached a permanent magnet. An aluminium cup mounted on a pivot, below and concentric with the spindle, carries a pointer. When the cup wheel rotates in the wind, the rotating magnet induces eddy currents in the aluminium cup which tries to turn in the same direction as the magnet against a restraining hair spring. The angular movement of the aluminium cup and the pointer gives a measure of the wind speed.

To use the instrument, the observer holds the anemometer at arms length with its axis vertical, with their arm at right angles to the wind direction to minimise interference from their body.