## 1 Introduction
To address this issue, the PEC-based technique is an option worth considering because of the external excitation source. Emerging from the foundation of EC sensors, PEC sensors boast a more recent origin, yet have witnessed rapid development in the past four decades. PEC sensors leverage conventional electrochemical techniques but incorporate a photoactive material on the electrode surface. The generated electron-hole pairs formed following suitable photon absorption by the photoactive material layer, caused by the electronic change state between the valence band and the conduction band, interact with the target analyte, generating a separate signal of the target analyte's redox reactions from the light excitation signal. This key distinction significantly reduces background noise, enhancing sensor sensitivity and lowering detection limits. Moreover, this method is relatively easy to use compared to other optical sensing methods, such as luminescence or fluorescence, because of the demand for complex image processing systems. However, despite their great potential for development, sensors based on photoelectrochemical techniques are only largely being developed in the laboratory environment due to insufficient photoconversion efficiency and the photobleaching effect [2]. Therefore, the development of this type of sensor is also associated with the interdisciplinary fields of material science and nanotechnology, which use semiconducting materials to improve the properties of photocatalytic sensing, serving many different applications [45; 46; 47]. EC and PEC sensors rely heavily on the potentiostat for analytical chemistry applications. This instrument plays a critical role by precisely controlling the applied voltage and capturing the electrical signals generated from redox reactions during analysis. While numerous reports detail laboratory-built potentiostats [48; 49; 50; 51], they are typically designed specifically for EC measurements. Conversely, most PEC studies utilize expensive, multifunctional commercial potentiostats with separate, non-integrated excitation light sources. This separation creates experimental setups that can be cumbersome and prone to inconsistencies. Recent advancements in PEC measurement systems are promising, exemplified by the portable lactate detection system developed by [PERSON] et al. [53]. Similarly, [PERSON] et al. [54] and [PERSON] et al. [55] have reported PEC systems designed for POC applications. However, these designs often cater to specific purposes and lack the versatility required for broader PEC research despite the similar characteristics of both methods, which can complement each other due to their merits during the development phase of sensor materials. Therefore, alongside the significant advancements in materials science enabling EC and PEC sensors, developing a universal measurement system capable of seamlessly handling both sensor types remains crucial to capture the merits of both sensors. This work presents a comprehensive design and development of a measurement system for EC and PEC sensing applications. The system incorporates a custom-designed measurement circuit that utilizes integrated monochrome light-emitting diodes (LEDs) as the excitation light source for PEC applications, an Android-based user interface developed for user interaction and data acquisition, and an experimental chamber designed to conduct the measurements. Experiments investigating potential PEC applications were conducted using copper (II) oxide (CuO) material synthesized via the hydrothermal method, serving as the photoactive material.