Product specifications

DS7911 (Rev. E, 1/4/07)
4-5
Perception and Wizard Sensors
7911
Anemometer
The Anemometer includes both wind speed and wind direction sensors.
Rugged components stand up to hurricane-force winds, yet are
sensitive to a light breeze. Includes sealed stainless-steel bearings for
long life. The range and accuracy specifications of this unit have been verified in wind-tunnel tests (information
available upon request). A model 7911 Anemometer reported wind speeds of 175 miles per hour before its tower
collapsed during hurricane Andrew, 1992. Digital filtering, with time constant as specified below, is applied to wind
direction measurements. In areas where icing of the anemometer is a problem, use Anemometer Drip Rings to deflect
water from the joint between moving parts.
General
Sensor Type
Wind Speed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wind cups and magnetic switch
Wind Direction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wind vane and potentiometer
Attached Cable Length . . . . . . . . . . . . . . . . . . . . . . . . . . 40' (12 m)
Note: On Monitor and Wizard stations, cable lengths longer than 140' (42 m) between sensors and console may artificially limit wind speed readings. That
is, beyond that length, maximum recordable wind speed decreases as cable length increases. For example, with a length of 140' (42 m), the maxi-
mum recordable speed exceeds 175 mph. At 240' (72 m), however, the maximum recordable speed drops to less than 140 mph. Below that upper
limit, however, the anemometer's accuracy is not affected.
Cable Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-conductor, 26 AWG
Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Modular connector (RJ-11)
Recommended Maximum Cable Length
Wizard and Monitor . . . . . . . . . . . . . . . . . . . . . . . . . 140' (42 m) Sensor to Console
Material
Wind Vane and Control Head. . . . . . . . . . . . . . . . . . UV-resistant ABS
Wind Cups. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Polycarbonate
Anemometer Arm. . . . . . . . . . . . . . . . . . . . . . . . . . . Black-anodized aluminum
Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.5" long x 7.5" high x 4.75" wide (470 mm x 191 mm x 121 mm)
Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 lbs. 15 oz. (1.332 kg)
Console Data
Note: These specifications apply to sensor output as converted by Davis Instruments weather station consoles.
Range
Wind Speed (large wind cups) (See Note 1). . . . . . . 2 to 150 mph, 2 to 130 knots, 1 to 67 m/s, 3 to 241 km/h
Wind Speed (small wind cups) (See Note 1) . . . . . . 3 to 175 mph, 3 to 150 knots, 1.5 to 79 m/s, 5 to 282 km/h
Wind Direction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0° to 360° or 16 compass points
Wind Run . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 to 1999.9 miles (1999.9 km)
Accuracy
Wind Speed (large wind cups) . . . . . . . . . . . . . . . . . ±2 mph (2 kts, 3 km/h, 1 m/s) or ±5%, whichever is greater
Wind Speed (small wind cups) . . . . . . . . . . . . . . . . . ±3 mph (3 kts, 5 km/h, 1.5 m/s) or ±5%, whichever is greater
Wind Direction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±7°
Wind Run . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±5%
Resolution
Wind Speed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 mph (1 knot, 0.1 m/s, 1 km/hr)
Wind Direction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1° (0° to 355°), 22.5° between compass points
Wind Run . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.1 m (0.1 km)