Enter 5 for Upper Level > Volts and 30 for Upper Level > EU.Choose ‘Engineering Unit Settings’ from the ‘Edit’ pull-down menu.In order to scale WinDaq to display wind speed in meters per second (m/s): The positive excitation wire (brown) will connect to the positive terminal of the supply, and the negative excitation wire (black) will connect to the negative terminal (as shown below). We’ll provide the 12 to 24V necessary to power the anemometer using a 12V DC supply (part # 101086). This puts the 250 Ohm shunt resistor in the 4-20mA loop, allowing for the 1-5V drop mentioned earlier. We’ll connect the positive output wire (yellow) to the positive (+) terminal of channel one, and the negative output wire (blue) to the negative (-) terminal. The anemometer has four connections a positive and negative output, and a positive and negative excitation (supply) connection. With the shunt resistor in place, we’ll connect the anemometer to the DI-2108-P. We’ll begin by connecting the 250 Ohm shunt resistor across channel one (+ to -). Loggers with bipolar ±5V measurement ranges like the DI-2008 or DI-4108 would also be suitable, albeit with half the resolution. The unipolar range maximizes the resolution of the measurement. We chose the DI-2108-P because of its programmable 0-5V unipolar measurement range. The 1-5 volt signal will be directly proportional to wind speed, where 1V = 0 m/s and 5V = 30 m/s (67 mph) Another alternative is to get a reference wind speed from a traditional rotating cup anemometer. As most of us do not have access to a calibrated wind tunnel, we can use the local weather forecast to provide a reference for the actual wind speeds.

In this demonstration, we’ll acquire and log wind speed data using an off-the-shelf anemometer with a 4-20mA output, a DATAQ Instruments model DI-2108-P and WinDaq data acquisition software.īecause analog voltage data loggers do not acquire current directly, we’ll use a 250 Ohm shunt resistor to convert the 4-20mA signal to 1-5V. The next step is to convert these readings into meaningful measurements of wind speed. Current is the same throughout the loop, regardless of background noise or wire length (I out = I in) Making a 4-20mA Measurement

Wind speed anemometer