A system for calibrating a device for measuring materials concentration in the blood, comprising: at least two sets,, of calibrating elements (105a-105d) (106a-106d), (107a-107d), each set comprising a plurality of calibrating elements, wherein each of the calibrating elements comprises: a first layer simulating specific human skin characteristics; a second layer comprising a specific concentration of one or more materials in the blood; wherein the specific human skin characteristics comprise at least one of: skin thickness, skin color, skin hair density, skin tone, skin temperature, skin optical properties and skin hair color, wherein in all calibrating elements in a set the first layer is the same first layer simulating the same specific human skin characteristics and each set of calibrating elements simulate different specific human skin characteristics, wherein each calibrating element in a set of calibrating elements comprises a different second layer comprising a different concentration of the one or more materials; and a controller configured to: receive illumination intensities from the device for measuring materials concentration when the device is attached to each calibrating element of the system; associate the received illumination intensities with the specific human skin characteristics and the specific concentration of the calibrating element to which the device is attached; and save the illumination intensities associated with the specific human skin characteristics and the specific concentration in lookup tables in memory of the device for measuring materials concentration, characterized in that each of the calibrating elements further comprises a third layer for simulating illumination reflection from a blood vessel in a skin tissue, wherein the third layer isolates the calibrating element from noise and reflections not related to the measured one or more materials in the second layer. at least two sets,, of calibrating elements (105a-105d) (106a-106d), (107a-107d), each set comprising a plurality of calibrating elements, wherein each of the calibrating elements comprises: a first layer simulating specific human skin characteristics; a second layer comprising a specific concentration of one or more materials in the blood; a first layer simulating specific human skin characteristics; a second layer comprising a specific concentration of one or more materials in the blood; wherein the specific human skin characteristics comprise at least one of: skin thickness, skin color, skin hair density, skin tone, skin temperature, skin optical properties and skin hair color, wherein in all calibrating elements in a set the first layer is the same first layer simulating the same specific human skin characteristics and each set of calibrating elements simulate different specific human skin characteristics, wherein each calibrating element in a set of calibrating elements comprises a different second layer comprising a different concentration of the one or more materials; and a controller configured to: receive illumination intensities from the device for measuring materials concentration when the device is attached to each calibrating element of the system; associate the received illumination intensities with the specific human skin characteristics and the specific concentration of the calibrating element to which the device is attached; and save the illumination intensities associated with the specific human skin characteristics and the specific concentration in lookup tables in memory of the device for measuring materials concentration, receive illumination intensities from the device for measuring materials concentration when the device is attached to each calibrating element of the system; associate the received illumination intensities with the specific human skin characteristics and the specific concentration of the calibrating element to which the device is attached; and save the illumination intensities associated with the specific human skin characteristics and the specific concentration in lookup tables in memory of the device for measuring materials concentration,