7817 7852 7859 7911 Sensors Spec sheet Mktg CD.fm
Anemometer
7911
SENSORS
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.
SPECIFICATIONS
General
Sensor Type
Wind Speed . . . . . . . . . . . . . . . . . .
Wind Direction . . . . . . . . . . . . . . . .
Attached Cable Length . . . . . . . . . . . . .
Cable Type . . . . . . . . . . . . . . . . . . . . . .
Connector . . . . . . . . . . . . . . . . . . . . . . .
Recommended Maximum Cable Length
Wizard and Monitor . . . . . . . . . . . .
GroWeather and EnviroMonitor . . .
Material
Wind Vane and Control Head . . . . .
Wind Cups . . . . . . . . . . . . . . . . . . .
Anemometer Arm . . . . . . . . . . . . . .
Dimensions . . . . . . . . . . . . . . . . . . . . . .
Weight. . . . . . . . . . . . . . . . . . . . . . . . . .
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Wind cups and magnetic switch
Wind vane and potentiometer
40’ (12 m)
4-conductor, 26 AWG
Modular connector (RJ-11)
. . . . . . . . . 140’ (42 m) Sensor to Console
. . . . . . . . . 250’ (75 m) from Sensor to SIM + 250’ (75 m) from SIM to Console
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UV-resistant ABS
Polycarbonate
Black-anodized aluminum
18.5" long x 7.5" high x 4.75" wide (470 mm x 191 mm x 121 mm)
2 lbs. 15 oz. (1.332 kg)
Console Data (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)
Measurement Timing
Wind Speed Sample Period . . . . . . . . . . . . . . . 2.25 seconds
Wind Speed Sample and Display Interval . . . . . 2.25 seconds (Monitor & Wizard)
Wind Direction Sample Interval . . . . . . . . . . . . 1 second (Monitor & Wizard)
Wind Direction Filter Time Constant (typical) . . 8 seconds (Monitor & Wizard)
Wind Direction Display Update Interval . . . . . . 2 seconds (Monitor & Wizard)
®
WeatherLink Data (These specifications apply to sensor output as logged and displayed by the WeatherLink.)
Wind Speed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Average during archive interval
High Wind Speed . . . . . . . . . . . . . . . . . . . . . . . . . . Maximum during archive interval
Wind Direction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Dominant wind direction during archive interval
Input/Output Connections
Black . . . . . . . . . . . . . .
Green . . . . . . . . . . . . .
Yellow . . . . . . . . . . . . .
Red . . . . . . . . . . . . . . .
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Wind speed contact closure to ground
Wind direction pot wiper (360° = 20 kOhm)
Pot supply voltage
Ground
NOTES
1.
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 maximum 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.
3465 Diablo Ave., Hayward, CA 94545-2778
( 510 ) 732-9229 • FAX ( 510 ) 670-0589 • sales@davisnet.com • www.davisnet.com
DS7911-00 (Rev. C, 11/11/04)
7911 Anemometer
SENSORS
INSTALLATION OPTIONS
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