Input impedance is a physical quantity that allows the objective characterization of wind instruments. It is now a common measurement in research labs and wind instrument factories. To be relevant, these measurements must achieve a precision higher than what a musician can detect. Although the sensitivity of musicians to slight impedance variations is not known, it is important to have an idea of the precision of impedance measurements in realistic situations. In order to evaluate the accuracy and different type of variability (e.g.: intra- and inter-operator) of impedance measurements and to identify key sources of error in the process, a collaborative study has been conducted involving multiple operators using the experimental setups developed by the CTTM. Measurements were performed on simple pipe geometries, including cylindrical, with a focus on boundary conditions, material properties, and calibration procedures. Variability in experimental results is linked to the calibration steps, the pipes manipulation, and challenges with wall surfaces, particularly in wooden pipes. The study also revealed significant inter-operator variability and emphasizes the importance of rigorous calibration procedures and standardized measurement practices. These findings provide actionable insights for enhancing the reliability of experimental methods and support further research into more complex and realistic geometries.