## 3 Materials and Methods
The data obtained with this oZm configuration is accurate to 0.1% for voltage measurements in a 42.5 to 57.5 Hz frequency range. In addition, the oZm v1 incorporates a customized version of the FFTW3 Fourier transform algorithm, which allows harmonic values to be obtained in complex form up to order 50, both for current and voltage. Given the compact and versatile aspect of the oZm, this implementation is of great relevance to the objectives of this work. This study used this meter to generate the DSUALM dataset (excluding harmonics) and the DSUALMH dataset (including voltage, current, and power harmonics up to the 50 th order). The oZm v3, shown in Figure 4, is an open-source three-phase meter designed for low-voltage installations, operating up to 400V and complying with IEC 61000-4-30 and EN 50160 standards. It measures single-phase and three-phase systems with 0.1% accuracy, supports DC systems, and operates at 50/60 Hz with a resolution of up to 10 MHz. The device features versatile current measurement capabilities, virtual analyzers, an intuitive web interface, and an open API, making it highly adaptable for various applications. Compared to its predecessor, the oZm v3 offers significant improvements, including higher accuracy, a 60 kHz sampling rate, and enhanced connectivity with GPS/PPS. It also incorporates programmable relays and multi-synchronization capabilities, making it ideal for power quality analysis and electrical grid monitoring. These enhancements enable more efficient detection and resolution of power quality issues and improved energy management in complex systems. Designed for a wide range of applications, including power quality monitoring, energy management, and electrical network analysis, the oZm v3 provides exceptional versatility. Its capability to measure single-phase and three-phase systems makes it suitable for diverse industrial and commercial environments. Its web interface and open API facilitate seamless integration with existing energy management systems, enabling real-time visualization and analysis of energy consumption and power quality. This functionality is crucial for optimizing energy efficiency and ensuring the reliable operation of electrical grids. This  
Figure 3: The block diagram of the oZm v1 (Source: own elaboration). new version of oZm was used in this study to generate the DSUALM10 dataset (excluding harmonics) and the DSUALM10H dataset (including voltage, current, and power harmonics up to the 50 th order). In this work, the Open Multi Power Meter (OMPM) [31] has also been utilized. The OMPM, whose electric sketch is shown in Figure 5, is a highly scalable multi-meter that employs a Node MCU ESP32 microcontroller (Espressif Systems, Shanghai, China), to acquire electrical measurements from a variable number of high-precision, low-cost PZEM004 modules (Peacefair, Shenzhen, China) connected via a bus. The prototype uses six PZEM 004T modules with Rogowski coils to measure current, power, voltage, and power factor for six devices. It offers a precision of 0.5% (1% for power factor) at frequencies above 10 Hz, transmitting data via RS-485. With high-resolution processing, the OMPM measures 80-260 V, 0-100 A, 0-23 kW, and 45-65 Hz per channel. The system supports up to 127 channels by adding more modules at minimal cost. The OMPM was designed with scalability, utilizing an RS-485 bus to transmit voltage, current, power, frequency, and power factor measurements from each module to the central controller via RX and TX lines. This setup allows for high accuracy and flexibility in electrical monitoring. It leverages the ESP32 microcontroller for data processing and stores data on microSD cards, with optional display capabilities via an I2C screen. Each module provides precise electrical measurements with an accuracy of 0.5% for most parameters, except for the power factor, which is 1%, achieved at frequencies above 10 Hz. This precision and scalability make the OMPM suitable for various applications requiring detailed electrical monitoring.