## 3 Measurement, Control, and Communication Architecture
### Custom-Designed Hardware Components
#### 3.1.2 Wind Speed Measurement  
The anemometer employed in this system is a three-cup, analog-output sensor designed to measure wind speed by converting the rotational velocity of its cups into a proportional voltage signal. This sensor operates within a supply voltage range of 12-24 V DC and outputs an analog voltage between 0 and 5 V, corresponding to wind speeds from 0 to 32.4 m/s. The uncertainty of the sensor is \(\pm\)0.3 m/s over the entire range of wind velocities for the measuring range (0 to 32.4 m/s), allowing for reasonably precise measurements in SWT applications. To interface the anemometer with the Arduino(r) microcontroller, the sensor's analog signal output is connected to the Arduino(r)'s analog input pin A3 (as shown in Figure 4). The sensor is powered using an external 12 V DC supply, with its ground (GND) tied to both the Arduino(r) and power supply grounds, ensuring a common reference point. The sensor's signal wire (typically blue) is connected directly to the analog input pin without \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Component in Figure 3** & **Name** & **Accuracy** & **Description** \\ \hline \multirow{6}{*}{1} & \multirow{6}{*}{LEM® LV 25-P} & \multirow{6}{*}{\(\pm\)0.9\% (of full scale)} & Voltage transducer used to measure the DC bus voltage after rectification. Outputs a scaled analog voltage proportional to the measured DC voltage. \\  & & & Hall-effect current transducer for non-invasive current measurement. \\  & & & \\  & & & Measures the current flowing through the DC line and provides an analog output. \\  & & & Isolated DC-DC converter that provides \(\pm\)15 V dual supply for the analog sensors. Ensures power isolation between the sensing circuit and the main board. \\  & & & Dual output power module that delivers regulated \(\pm\)15 V from a 12 V input, supplying power to the transducers with electrical isolation. \\  & & & Series resistor connected to the primary side of the LV 25-P for input scaling and current limitation. \\  & & & Converts the output current of the \\  & & & LV 25-P into a proportional voltage signal for analog acquisition. \\  & & & Converts the output current of the \\  & & & LA 55-P into a proportional voltage signal for analog acquisition. \\ \hline \hline \end{tabular} \({}^{1}\) typical value.  
\end{table} 
Table 2: Components of the voltage and current measurement board. the need for additional signal conditioning, because the Arduino(r)'s analog input range is compatible with the sensor's output voltage. Calibration of the sensor involves determining the minimum voltage output when the anemometer is stationary. In practice, this value may not be exactly 0 V due to sensor characteristics and environmental factors. In fact, a measured minimum voltage of approximately 0.054 V has been observed under no-wind conditions. This offset voltage is subtracted from subsequent readings to ensure accurate wind speed calculations. The wind speed (\(v\)) in meters per second (m/s) is calculated from the analog voltage (\(V\)) using a linear mapping based on the sensor's specifications:  
\[v=\left(\frac{V-V_{min}}{V_{max}-V_{min}}\right)\times v_{max} \tag{12}\]  
where:  
* \(V\) is the measured analog voltage;
* \(V_{min}\) is the offset voltage under no-wind conditions (e.g., 0.054 V);
* \(V_{max}\) is the maximum output voltage of the sensor (5 V);
* \(v_{max}\) is the sensor's maximum wind speed range (32.4 m/s). This linear relationship approximates the sensor's behavior based on manufacturer specifications, although minor deviations from ideal linearity may occur due to sensor tolerances and environmental factors. Nonetheless, the resulting uncertainty remains acceptable for typical SWT monitoring and control tasks. The output voltage is sampled using the Arduino(r)'s 10-bit analog-to-digital converter (ADC), which provides digital values from 0 to 1023.