Anemometer beam exits reflect, or backscatter, the light back into a detector, where it is measured relative to the original laser beam. When the particles are in great motion, they produce a Doppler shift for measuring wind speed in the laser light, which is used to calculate the speed of the particles, and therefore the air around the anemometer. Ultrasonic anemometers, first developed in the 1950s, use ultrasonic sound waves to measure wind velocity. They measure wind speed based on the time of flight of sonic pulses between pairs of transducers. Measurements from pairs of transducers can be combined to yield
Alcoholic spirits measure used in Scotland and Northern Ireland. The landlord can chose one or the other but not both. Thimble measures are also used in 175ml and 250ml volumes for measuring wine. Although government stamped for the correct volume, the thimble measure does rely on the user measuring the wine out manually into the thimble. Alcoholic spirits measure Alcoholic spirits measures are instruments designed to measure exact amounts or shots of alcoholic spirits. The most common products used today to measure spirits are the thimble measure and the non-drip measure, often referred to as an optic. The terms "Optic", "Optic Pearl", "OpticJade"