The article deals with description of design of sensor system for linear actuators. These constitute a part of a parallel kinematic machine based on a structure of a Stewart platform. The machine is intended for testing of bone implants in biomechanical and medical practice. The developed Stewart platform presents a mechatronic system. Hence the design of mechatronic systems known as a V-model was used. The system of sensors has been developed since the middle phase of the Stewart platform development.