Voltcraft bl 30 an anemometer voltcraft bl 30 an p the voltcraft bl 30 an anemometer is a handy impeller meter with a low loss magnetic collector for measuring the speed of wind and gas flow rate the speed can be displayed in five different units m s ft min km h mile h and knots on the display moreover the average speed or maximum speed of each measuring process can be determined and displayed on an illuminated display the bl 30 is powered by a 9v battery p voltcraft bl 30 an anem