A portable biometric wrist device and a method for manufacturing thereof

A method for manufacturing a portable biometric wrist device having a casing, wherein all the components of the portable biometric wrist device are installed in the casing, and an optical sensor, the method comprising

• providing
• at least one light source and at least one light detector installed onto a circuit board,
• the 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, and
• an elastic sealing plate comprising elastomer arranged to fit 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, and
• combining said circuit board, said sealing plate and said casing so that said at least one light source and said at least one light detector fit to the apertures in the sealing plate for optically isolating said at least one light source and said at least one light detector from each other inside said casing.