All you need to know about the IM159 Handheld Anemometer

The IM159 is a solidly built instrument made from non-ferrous metal, which is used to measure wind speed. The wind speed is shown on an analogue scale and this can be calibrated in knots, metres per second or miles per hour. When calibrating the instrument we use a wind tunnel to ensure that the readings given by the analogue scale are accurate. We are also able to provide you with a calibration certificate, so that you may have a copy of the test results and this complies with the requirements of CAP 437.

The IM159 is a mechanical instrument and requires no battery or form of electricity. This makes it safe to use in explosive zones. It is manufactured to British Meteorological Office specifications (ref. 23510) and is ideally suited for use as a secondary device in case automated sensors become unavailable.

In terms of calibration, it is advised that the IM159 should be serviced annually, as it will ensure that your instrument is in the correct condition and reading accurate results. This type of assurance is needed when you are using your instrument as a contingency device in an airport or military environment.

This is emphasised in CAP 437: Standards for offshore helicopter landing areas, as it states that:

‘It is recommended that a hand-held anemometer is used as a back-up in case of the failure or unavailability of the automated sensors; any readings that are taken should be taken from the centre of the helideck. The pilot should be advised that a hand-held anemometer has been used to estimate the wind speed and a remark should be added to the offshore weather report form.’

It is important to follow these guidelines if you have UK registered helipad, otherwise you may be penalised. To read an online copy of these standards by the Civil Aviation Authority, please click here.


If you would like to receive further information about the IM159 Handheld Anemometer, please get in touch via email ( or phone (+44 (0) 20 8551 7000).