In electromechanical motion systems performance measures such as positioning accuracy, dynamic stiffness and control bandwidth are severely limited by backlash. Several control schemes based on backlash compensation or switching control of hybrid systems are known, but many of these approaches require the exact backlash width as an input parameter. Several existing approaches for backlash identification are limited in accuracy because the load-side velocity is required but it is not directly measurable. In this paper a method for backlash identification tailored to electromechanical motion systems with rotary motor and translationally moving load is proposed. A mobile sensor board with inertial measurement unit (IMU) is mounted temporarily on the load and serves to acquire the accelerations during the experiment. The connection to the host-PC is wireless, time synchronisation is not required. It is shown in experiments on a testbed with an adjustable backlash coupling but otherwise i ndustry-like equipment that high accuracies can be achieved.