An open-source test stand for backlash measurement in low-cost UART servo motors

Backlash in compact servo actuators is a common source of positioning error in low-cost robotic and mechatronic systems. Measuring this backlash reliably is difficult because most servos include only a single output-shaft encoder, and conventional tools such as dial indicators can introduce enough probing force to distort the measurement. We present an open-source test stand that applies small, repeatable loads to a servo lever and measures the resulting displacement under both loaded and unloaded conditions. The stand uses low-cost components, 3D-printed fixtures, interchangeable levers, and a soft elastic coupling to apply controlled forces in opposite directions. Accompanying software coordinates the test sequence, records telemetry, and analyzes backlash using a consistent, repeatable methodology. We demonstrate how the platform can characterize single-servo and coupled-servo configurations, enabling direct comparison of mechanical performance and aiding actuator selection in design work. All CAD files, control software, and analysis tools are openly provided to support replication and further development.