| Power supply | 9-18 volts DC at 23 mA (average) |
| Display | 42 light emitting diodes arranged as 2 dials, one for speed
(18 LEDs)
and one for direction (24 LEDs). Direction LEDs are at 15 degree intervals. Speed units and full-scale speed are determined by the builder of the anemometer. Speed LEDs are at (Calibration Speed /10) intervals. Rev 5 and later FW: If speed off scale and less than 2.55 x calibration speed, autoranges to 2X scale and speed dial LEDs flash. Power to the LEDs is pulse width modulated to control brightness. This allows visual interpolation of values between LED positions. Thus direction can be read to within a few degrees and speed read to typically 1 or 2 km/hr. Brightness level is suitable for indoor viewing if standard LEDs are used, or outdoor viewing (in all but the worst conditions) if ultra bright LEDs are used. |
| Serial port | Standard DB9(F) connector. 1200 baud, 8 data bits, 1 stop bit, no status or flow control signals. |
| Sensor-to-display-unit connection |
Current loop, plain "figure 8" type 2 core wire, max length > 30 metres |
| Sensor type | Rotorvane with optically sensed rotation |
| Resolution | Direction 1/256 of a circle, about 1.4 degrees. Speed |
| Accuracy | Direction Software algorithms +/- 2 degrees. (see FAQ). Sensor typically +/- 2 to +/- 15 degrees, depending on accuracy of construction and bearing friction. Speed |
| Data logged (accessible via serial port) |
Max gust speed and direction. Speed distribution, average speed each 10 minutes, 20 bins, one for each 1/20 of calibration speed. Bin capacity 65535 counts, restart from 0 on count 65536. Direction distribution by distance run, 8 bins. Bin capacity 65535 counts, restart from 0 on count 65536. |
| Display case dimensions |
Minimum size 130 mm (W) x 67 mm (H) x 43 mm (D) |
Related information
The graph below shows the error in wind direction reading of an anemometer which was constructed according to these plans. The graph is for a wind speed of nine knots. At higher speeds the errors are similar. At three knots the errors are larger.