Measurement Issues with LED Signal Applications

The use of LEDs is now widespread through the road and transport industries. The great majority of these applications have to comply with national or international standards and regulations. The photometric and colorimetric measurement of such LED applications require different techniques and procedures than that used for the more mature incandescent-based applications. Standards and Regulations need to be informative about the tolerance they place on specifications, and measurement laboratories have to take into account their measurement uncertainty when testing compliance to a standard.

This paper will highlight the techniques and equipment that need to be used to obtain reliable results with low measurement uncertainty. The paper also addresses a means of estimating the uncertainty of measurement for colour. A discussion of the need for regulations to include restrictions on sun-phantom and veiling glare will be given.