The main motivation of paraglider pilots is to stay in the air for as long as possible. Therefore, paraglider pilots are always searching for thermal upwind that allow them to gain altitude. These thermal lifts are difficult to detect. Therefore, sensors and devices that indicate the vertical speed (so-called variometers) are widely used among paraglider pilots. This article presents the design and the implementation of an ultralow-power, self-sustaining, high-precision, wrist-worn variometer with a minimal form factor but infinite lifetime, which can visually and acoustically indicate the vertical velocity. This article demonstrates the benefits of combining multisource energy harvesting (EH) for wearable devices with low power design, exploiting a novel near-threshold ARM Cortex-M4F microcontroller, the Ambiq Apollo2, for the onboard processing. The experimental results show a power consumption of only $17.12~\mu \text{W}$ in sleep mode and $1937.21~\mu \text{W}$ in the worst case scenario when processing the data and outputting an audio feedback. Measurements confirmed that combining both thermal and solar EH makes the designed electronics self-sustaining. Without EH, the system will be operational for up to 372 h in always-on mode (worst case scenario) supplied by a 200-mAh lithium-ion battery.

中文翻译：

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Piepser 2.0：一种自我维持的智能手表，可最大限度地延长滑翔伞飞行时间

滑翔伞飞行员的主要动机是尽可能长时间地在空中停留。因此，滑翔伞飞行员总是在寻找使他们能够获得高度的热逆风。这些热升力很难被检测到。因此，指示垂直速度的传感器和设备（所谓的变率计）在滑翔伞飞行员中被广泛使用。本文介绍了一种超低功耗、自我维持、高精度、腕戴式变仪的设计和实现，该变仪具有最小的外形尺寸但具有无限的使用寿命，可以在视觉和声学上指示垂直速度。本文展示了将用于可穿戴设备的多源能量收集 (EH) 与低功耗设计相结合的好处，利用一种新颖的近阈值 ARM Cortex-M4F 微控制器 Ambiq Apollo2 进行板载处理。实验结果表明，在处理数据和输出音频反馈时，睡眠模式下的功耗仅为 $17.12~\mu\text{W}$，最坏情况下的功耗仅为 $1937.21~\mu\text{W}$。测量证实，结合热能和太阳能 EH 使设计的电子设备能够自我维持。如果没有 EH，系统将在由 200 mAh 锂离子电池供电的始终开启模式（最坏情况）下运行长达 372 小时。