Various wearable health monitoring devices are described herein. Some implementations include one or more emitter chamber covers injection molded out of a first material comprising transparent glass, one or more
detector chamber covers injection molded out of a second material comprising transparent glass, and a
light barrier construct injection molded out of a third material over the one or more emitter chamber covers and the one or more
detector chamber covers. The third material may be opaque and can comprise glass and an optically absorbing
pigment. Some implementations include a circuit board, emitter(s) mounted to the circuit board and arranged within the emitter chamber cover(s), and
detector(s) mounted to the circuit board and arranged within the detector chamber cover(s). The circuit board, emitter(s), detector(s), emitter chamber cover(s), and detector chamber cover(s) can form part of a sensor
assembly connected to a housing of the wearable health monitoring devices.