Connecting Davis wind speed and direction sensors to a Vernier interface is fairly complicated DIY project. It is a whole lot easier to use our Anemometer (ANM-BTA).
The Davis wind speed sensor functions as digital sensor and could be connected to a Vernier interface using a BTD connector. The Davis wind direction sensor as an analog sensor, and could be connected to a Vernier interface using a BTA connector. They can be used separately or together.
Internally, the Davis wind speed sensor uses a simple electrical contact, wherein the circuit is completed once for every rotation of the device. The wind direction sensor uses a 20-k ohm potentiometer connected to the free-spinning indicator so that the output voltage varies with the wind direction.
In order to use the Davis sensors with a Vernier interface, some pins from each device must be connected. The common ground pins from the Vernier BTA and BTD connectors (pins 2 and 5, respectively) both go to the red pin on the Davis RJ14 connector (pin 4).
The +5V power pin from the BTA connector (pin 5) goes to the yellow RJ14 pin (pin 2).
The green signal output pin from the RJ14 connector (pin 3) goes to the SIG1 input pin on the BTA connector (pin 6).
The +5.3V power pin (with a resistor) and the DIO0 input pin from the BTD connector (pins 4 and 1) both go to the black pin on the RJ14 connector (pin 5).
We have created a Logger Pro file for this use. If you want to create your own file, here is how to do it. For wind direction set up a Raw Voltage (0 to 5V) sensor. Create a New Calculated Column which is Wind Direction as Voltage *69. For wind speed, set up a radiation monitor with a sample time of 2 seconds. Set up a New Calculated Column with a definition of Count *0.3064. These numbers are approximate and we did not spend a lot of time calibrating.