In some implementations, a device includes light emitter(s) to emit first light having a first wavelength and second light having a second wavelength. The device also includes light detector(s) to generate a first electrical signal while the light emitter emits the first light, a second electrical signal while the light emitter emits the second light, and a third electrical signal while the light emitter is not emitting light. The device also includes ambient light cancellation circuit(s) to generate a countering signal to counter a portion of one or both of the first and second electrical signals based on the third electrical signal. The device also includes analog to digital converter(s) to generate first and second digital signals based on values of the first and second electrical signals, respectively. The device further includes a controller to determine a saturation of peripheral oxygen metric based on the first and second digital signals.