A portable biometric wrist device having an optical sensor and including at least one light source and at least one light detector installed onto a circuit board, a casing having at least one aperture for said at least one light source and at least one aperture for said at least one light detector, wherein each of said at least one light source and at least one light detector are optically isolated from each other inside said casing with a sealing plate between said casing and said circuit board, said sealing plate having at least one aperture for said at least one light source and at least one aperture for at said least one light detector. The present invention also provides a method for manufacturing said portable biometric wrist device.
