"Gill Instruments Ltd WindMaster ultrasonic anemometer"@en . . "SDN:L22::TOOL0616" . "Three axis ultrasonic anemometer offers sonic temperature, speed of sound and wind vector outputs at 20 Hz (32 Hz option). The instrument measures the time taken for an ultrasonic pulse of sound to travel from an upper transducer to the opposite lower transducer, and compares it with the time for a pulse to travel from lower to upper transducer. It has an aluminium/carbon fibre construction and will monitor either 0-60 m/s (0 - 134 mph) or 0-45 m/s (0-100 mph) wind speed depending upon the model. The units of wind speed, output rate, and formats are all user selectable. There are several optional analogue outputs and inputs depending on the model. Windspeed accuracy is 1.5 percent root mean squared (0 - 20 m/s) and wind direction accuracy is 2 degrees at less than 25 m/s."@en . .