Wind direction

The wind vane is coupled to a 10 kΩ potentiometer, which has a 5-degree electrical dead band between 355 and 360 degrees. A 1 MΩ resistor between the signal and ground pulls the signal to 0 mV (0 degrees) when wind direction is in the dead band (between 355 and 360 degrees).

Wind direction is measured by the BRHalf() instruction.

Some CRBasic measurement sequences can cause the measurement of the wind direction to return a negative wind direction (–30º) while in the dead band. To overcome this problem, all program examples use a delay of 20 ms (20,000 μs) and set any negative wind direction values to 0.0: If WindDir < 0, then WindDir = 0.0.

The excitation voltage, range codes, and multipliers for the different data logger types are listed in Parameters for wind direction. Wind direction measurement theory has additional information on the BRHalf() measurement instruction.

Parameters for wind direction
	CR300 Series	CR800, CR850, CR1000	CR1000X	CR6	CR3000
Measurement range	mV2500	mV2500	mV5000	mV5000	mV5000
Excitation voltage	2500 mV	2500 mV	2500 mV	2500 mV	5000 mV
Reverse excitation	NA	True	True	True	True
Delay or settling time	20000 µs	20000 µs	20000 µs	20000 µs	20000 µs
Multiplier	355	355	355	355	355
Offset	0	0	0	0	0