Joint movements are the key factor for the mobility of the people during daily activities. The evaluation of the joint movements is determined by the range of motion (ROM) parameters. The ROM might change due to age, gender, and some diseases. Therefore, it is essential to measure ROM accurately and compare it with the normal values of the healthy people. In this study, a low-cost, wireless, and wearable electrogoniometer was designed for highly precise and accurate measurements. The stability of the measurements is guaranteed with the quaternion based Kalman filter. The measurements of the developed system are compared with the traditional goniometer. The concordance correlation coefficient is calculated as a similarity metric, and the result is obtained as $1$. In addition, a GUI was prepared to present 3D visualization of the movements in real-time with the ROM measurements and give visual feedback to the physiotherapists during physical examinations and to the patient during the home therapy sessions. The measurements also can be recorded using the GUI for retrospective analysis.

关节运动是人们在日常活动中活动能力的关键因素。关节运动的评估由运动范围 (ROM) 参数决定。ROM 可能会因年龄、性别和某些疾病而改变。因此，准确测量 ROM 并将其与健康人的正常值进行比较至关重要。在这项研究中，设计了一种低成本、无线和可穿戴的电子测角仪，用于高精度和准确的测量。基于四元数的卡尔曼滤波器保证了测量的稳定性。将开发系统的测量结果与传统的测角仪进行比较。计算一致性相关系数作为相似度度量，得到的结果为$1$. 此外，还准备了一个 GUI，以通过 ROM 测量实时呈现运动的 3D 可视化，并在身体检查期间向物理治疗师和在家庭治疗期间向患者提供视觉反馈。还可以使用 GUI 记录测量结果以进行回顾性分析。