This article introduces the Index of Internal Effort (IIE) as a generic metric applicable across various areas of systems engineering, including mechatronic systems. To demonstrate its application, we selected a dataset encompassing both software and hardware, and presented two possible approaches for its utilization. In selecting the measurement variables, we employed Spearman's correlation test to mitigate potential biases. The obtained results are promising, as the IIEa, an approximation of IIE complexity, managed to measure Arduino platform code similarly to classical metrics such as Lines of Code (LoC) and Cyclomatic Complexity (CC). Additionally, in evaluating the hardware within the selected dataset, the IIEa showed a significant positive correlation with two original variables from the dataset: (V1) the time required for experiment execution and (V2) the experiment's difficulty. The primary conclusion from this proof of concept is that the IIEa possesses a robust framework for measuring Explicit Intellectual Activities (EIA), such as programming code and electronic circuits. However, as IIE is a generic framework, further testing in other areas is necessary to identify any potential limitations or adaptation needs. Although not tested in the mechanical aspect of projects due to lack of mechanical design data, the IIEa demonstrates potential in this regard, given its generic structure for complexity measurement.
