###### Abstract  
Gear condition monitoring is predominantly executed through the utilization of acceleration sensors positioned on the housing. However, recent advancements have identified measuring the instantaneous angular speed as a compelling alternative as it shortens the transmission path and therefore provides high-quality rotational angle information that can be used to increase damage prediction accuracy, particularly under transient operating conditions. Additionally, there are a variety of methodologies for integrating sensors into gears, which underscores the necessity for high-quality condition data. However, it should be noted that a significant amount of effort is required to successfully integrate these sensors into the rotating system. This publication uses a gear wheel sensor that employs the gear itself as a material measure to acquire rotational angle data and to deduce the damage condition. A magnetoresistive sensor is integrated into the gearbox housing radially facing a ferromagnetic gear and measures the rotational angle by the gear teeth. Various artificial tooth flank damages are applied to the pinion. The rotational angle is measured with the gear sensor, and the damage state is classified with a random forest classifier using established evaluations in the time and frequency domains. The tests are conducted under stationary operating conditions at an array of speed and torque levels. Additionally, they are performed under transient operating conditions, employing speed ramps at constant torque. The results of the classification are evaluated by means of classification accuracy and confusion matrices and compared with those obtained via a classic encoder at the pinion shaft and an acceleration sensor at the gearbox housing. c 2025 15 6446 2025 1 <concept> <concept  
Therefore, condition monitoring facilitating rotational angle measurement has received interest in recent years. Teeth damage at helical gears and a broken tooth at a spur gear can be detected with optical rotation angle sensors [1]. Present publications utilize a wide range of resolutions for the rotational angle sensors, ranging from 60 pulses per revolution [2] to 5000 pulses per revolution [3]. This enables the detection of damage with both systems. A comparative analysis between a high-end and low-end configuration has been conducted [4]. They confirm that both systems can detect damage, but the high-end setup provides a significantly higher signal-to-noise ratio. Additionally, a study has been conducted on the classification of cracks, wear, chipped, and missing teeth under stationary and transient operating conditions on spur gearboxes [5; 6]. As an extension to utilizing a single rotational angle sensor, the implementation of two rotational angle sensors facilitates the assessment of transmission error [7; 8] for the purpose of quantitative wear measurement. An intensive analysis of rotational angle measurement is provided in a review [9]. Rotational angle measurement provides high-quality information with a short transfer path to the gears, which is of interest for gear condition monitoring. In addition to measuring the angle of rotation, there are also various approaches to integrating sensors into a gear [10; 11]. However, the wireless sensors cannot be supplied directly with energy and must therefore be installed in a manner that maximizes energy efficiency. To this end, the microcontrollers employed must also be optimized, for instance, by decreasing the sampling rate [12]. Moreover, the selection of the sensor position is paramount for achieving an optimal signal-to-noise ratio. Research has demonstrated that higher amplitudes can be measured directly on the gear compared to the housing. This allows for the observation of damage-specific frequencies, particularly at low speeds [13]. Furthermore, the integration of the sensor into a gearwheel can potentially compromise the integrity of the gearwheel itself, which must be taken into account when integrating the sensor [14].