Sun / UV Penetration and Protection Measurement System - Technical Notes

The system comprises a Camspec M550 double beam scanning spectrophotometer controlled by a PC with comprehensive Windows® software with an integrated sphere accessory installed.

The Sun / UV Penetration System for fabrics has been designed specifically for analysts working in the fabric industry who need an accurate and reliable method of determining the sun blocking properties of fabrics for the important UV-A and UV-B wavelengths.

Sun Protection Measurement System

Standards
This system is for measuring the sun blocking properties of fabrics and fully conforms to European Standard EN 13758-1, American (AATCC Test Method 183.1998), British (BS 7914:1998) and Australian and New Zealand (AS/NZS 4399:1996) test methods. The appropriate method should be read in full by those intending to make formal measurements.

Explanation (h = lambda)
The human skin is sensitive to ultraviolet (UV) radiation wavelengths up to 400nm. The Sun's radiation normally reaches the Earth comprising of wavelengths down to 290nm. Measurements are therefore made from 290nm to 400nm in order to determine the effects of the Sun's radiation to the human skin.

The type 1 skin's sensitivity has been measured and averaged over many subjects to produce the CIE Erythemal Effectiveness tables which give the relative spectral effectiveness Eh at 5nm intervals from 290 to 400nm. High values mean that the skin is affected by light of that wavelength.

The Sun's spectral irradiance Sh has been measured at noon midsummer for the most intense radiation to be expected. This has been done at noon 17 January 1990 in Melbourne (38degrees south) and noon 3 July in Albuquerque, New Mexico.

The product EhSh summed at 5nm intervals from 290 to 400nm is a measure of the erythemally effective solar UVR irradiance E' (W.m-2).

Fabric covering the skin reduces the Sun's rays by a proportion T? the transmittance of the fabric. The product EhShTh measured at 5nm intervals from 290 to 400nm is a measure of the erythemally effective solar irradiance with the fabric present E.

The penetration factor P = E/E', is a measurement of the proportion of erythemally effective radiation penetrating the fabric.

The UV protection factor UPF = E'/E is a measurement of the protection given to the skin by the fabric.

Measurement

The sun protection measurement system measures the transmittance of the fabric from 290 to 400nm and then the PC computes the penetration factor or ultraviolet protection factor depending on the requirement of the standard used.

As the fabric scatters the light, in order to measure all the light which is transmitted through the fabric, an integrating sphere is used.

The sphere is made of a highly reflective white matt material as Opdima which diffusely reflects over 96% of the light. This collects all the light transmitted by the sample, and reflects it round the sphere until a proportion reaches the photodiode detector. The sphere is baffled to prevent the direction illumination of the detector by either light scattered from the sample or light scattered by the rear surface of the sphere when the sample is absent. The ratio of the light reaching the detector with and without the sample gives the transmittance of the fabric at that wavelength.

See diagram here.

Ref - ERROR CORRECTION AND CALIBRATION OF A SUN PROTECTION MEASUREMENT SYSTEM FOR TEXTILE FABRICS
A. R. L. Moss
Radiation Protection Dosimetry
Vol 91, Nos 1-3, pp 261-264 (2000)
Nuclear Technology Publishing

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Range by Model

Single Beam
M105
(Student Visible Range)
M106
(QC / Student Visible Range)
M107
(High Specification Visible Range)
M108
Programmable Visible Spectrophotometer
M508
Basic Programmable UV/Visible Spectrophotometer
M501
(UV / Visible Spectrophotometer)

Double Beam
M550
(UV / Visible Spectrophotometer)

Special Systems
M550N
System for Measuring NATO colours of paints and fabrics.
M550 SPF
System for measuring sun protection factor of fabrics.