Abstract: Electrodes that can be used to determine a first type of physiological signal and a second type of physiological signal are disclosed. The first type of physiological signal can be electromyography (EMG) signals produced by activity of muscles and tendons. Identification of hand movements can be supplemented with pose detection circuitry such as inertial measurement units (IMUs). These EMG signals can be processed to identify hand movements and recognize gestures associated with those hand movements. The second type of physiological signal can be electromyography (ECG) signals produced by the heart. The electrodes can be used to detect EMG and ECG signals dependent upon a current configuration of sensing circuitry. The electrodes can be used to determine a measurement quality associated with the EMG signals.

Abstract: A photoplethysmographic (PPG) device is disclosed. The PPG device can include one or more light emitters and one or more light sensors to generate the multiple light paths for measuring a PPG signal and perfusion indices of a user. The multiple light paths between each pair of light emitters and light detectors can include different separation distances to generate both an accurate PPG signal and a perfusion index value to accommodate a variety of users and usage conditions. In some examples, the multiple light paths can include the same separation distances for noise cancellation due to artifacts resulting from, for example, tilt and/or pull of the device, a user's hair, a user's skin pigmentation, and/or motion. The PPG device can further include one or more lenses and/or reflectors to increase the signal strength and/or and to obscure the optical components and associated wiring from being visible to a user's eye.

Abstract: An electronic device such as a wristwatch may be provided with conductive structures. The conductive structures may include a sensor electrode for an electrocardiogram (ECG) sensor. A coating may be disposed on the sensor electrode to reflect particular wavelengths of visible light so that the sensor electrode exhibits a desired color. The coating may include adhesion and transition layers on the sensor electrode, an opaque coloring layer on the adhesion and transition layers, and a thin-film interference filter on the opaque coloring layer. The thin-film interference filter may have an uppermost diamond-like carbon (DLC) layer. The DLC layer may contribute to the color response of the coating while concurrently minimizing noise in ECG waveforms gathered by the ECG sensor using the sensor electrode.

Abstract: Embodiments are directed to devices, systems and methods for determining a perspiration metric of a user. In some embodiments, a device may include a perspiration sensor having first and second electrodes positioned on a skin-facing exterior surface of the device. Capacitance circuitry may measure a capacitance between the electrodes, which may be used to calculate the perspiration metric. In some embodiments, the device defines a cavity such that one or both of the electrodes extend at least partially into the cavity. Other embodiments include a second perspiration sensor, and measurements from the second perspiration sensor may be used in calculating the perspiration metric.