## 1 Introduction
As shown, I-V measurement techniques range from current and voltage sensors coupled to microcontrollers (e.g., Arduino, Raspberry Pi, and PIC) to more sophisticated equipment such as oscilloscopes, National Instruments (NI) data acquisition systems, and digital multimeters. Regarding load control, various methods have been employed, including MOSFETs, charge controllers, capacitive loads, and programmable electronic loads. While Arduino-based systems have  
been frequently used for I-V measurement, they are typically combined with separate load control mechanisms. As shown, few systems provide full integration of voltage and current measurement with automated resistive load switching using a single microcontroller. For example, in [17], a resistive load is used alongside an Arduino for I-V measurement, but the resistance is manually adjusted. The novelty of this work lies in the development of a low-cost, standalone Arduino-based DAQ system that integrates measurement, load variation, and data storage. Using a relay-controlled resistor bank and programmed switching logic, the system provides real-time I-V characterization without manual adjustments or external software dependencies. It offers a scalable and reproducible tool suitable for academic, research, and field applications in renewable energy monitoring. This work presents a low-cost, Arduino-based I-V curve tracer with automated resistive load switching, designed to provide fast, real-time PV panel characterization under field conditions. The proposed system integrates load control and data acquisition in a single platform, eliminating the need for manual adjustments and enabling rapid I-V curve generation. Experimental validation was conducted using a commercial PV module under natural solar conditions, with results compared to a single-diode model for performance evaluation and parameter optimization. The Arduino-based system, which integrates automated relay-based switching with a bank of fixed resistors, offers a unique balance of automation, speed, low cost, and stability that distinguishes it from other common approaches. Manual methods, which rely on manually switching fixed resistors [17] or adjusting rheostats, are inherently slow. Characterizing PV panels under real-world field conditions requires rapid data acquisition to account for the unpredictability of environmental factors like solar irradiance and temperature. A slow acquisition process increases the likelihood that the panel is exposed to varying conditions during a single test, which compromises the validity of the resulting I-V curve as it no longer represents a stable operating point. The proposed system directly solves this problem by automating both the load variation and the data acquisition. Compared to commercial electronic loads, they offer high precision and are often prohibitively expensive. Our system stands out primarily due to its low cost, making PV characterization accessible for educational, research, and resource-limited applications. Furthermore, many commercial units are not designed for \"rapid field deployment\" due to their size, weight, and power requirements. Our system is highly portable and requires no external power beyond a laptop's USB port, facilitating easy data collection in the field. Lastly, its open-source hardware and software design allows it to be \"easily replicated and adapted\" to various experimental needs, offering a level of flexibility not available with proprietary commercial systems. Compared to MOSFETs systems, although MOSFETs can provide a more continuous load variation, they require more complex analog control circuits (e.g., PWM with filtering and current/voltage feedback) to ensure stable operation across the entire range. Calibrating and linearizing this control can be challenging. Additionally, high-power MOSFETs require large heat sinks, often with active cooling, to dissipate power. In contrast, the proposed system provides a known, fixed, and highly repeatable resistive load for each measurement point.