An infrared light beam senses the turbine’s rotation with no added friction, permitting  a high degree of accuracy. Large scale integrated circuitry adds to the Turbo Meter’s reliability. One switch allows the user to move between four different scales that determine air velocity in feet per minute, meters per second, miles per hour or knots. The three-digit LCD readout offers superb contrast and visibility, especially important for industrial applications where lighting is poor. An auto-off function prevents unnecessary battery drainage. www.davisnet.com