• In a light breeze, read across from the white ball to the scale on the left. The Venturi meter measures wind speed in kilometres an hour.
• In a strong wind the white ball will rise to the top of the tube. Use your finger to cover the top of the red tip and read across to the scale on the right.

Do's and Don'ts

	Hold the Venturi meter perfectly vertical - that's straight up and down.
	Be gentle with the instrument.
	Don't use it to dig in the sand.

How it Works

The Venturi meter has a narrow tube running from top to bottom, with a small opening at the top. When the wind blows over the top of the instrument a slight vacuum is created in the tube and the white ball is sucked up. The stronger the wind, the greater the suction and the further up the tube the white ball will travel.

This phenomenon is known as the Bernouilli principle and is named after Daniel Bernouilli, a Swiss scientist who first described it more than 200 years ago. The Venturi meter is named after Italian physicist Giovanni Battista Venturi (1746-1822).