Standard MOT/08/19/1 specifies that instruments for measuring smoke emissions must be calibrated using glass neutral density filters with accurately known transmittance values
Reducing vehicle emissions is one of the many steps being taken to ward off climate change, and from 4 February 2008 London will have a Low Emission Zone, or LEZ, and excessively polluting vehicles will have to pay a daily charge of up to £200 to drive within this area.
One of the tests applied to diesel vehicles is a smoke emissions test, similar to that conducted routinely during MOT (roadworthiness) testing.
It is clearly essential, in view of the financial and legal implications, that the instruments used to perform these tests are accurately calibrated.
In the UK, standards for emissions testing are set by the Vehicle and Operator Services Agency (Vosa), an agency of the Department of Transport.
Many instruments for measuring smoke emissions work on an optical principle, and Standard MOT/08/19/1 specifies that these must be calibrated using glass neutral density filters with accurately known transmittance values - with a tolerance range of not more than +/-3% from a nominal value.
These values must be traceable to internationally recognised references.
Starna Scientific was approached by a leading manufacturer of emissions testing instruments, and was able to readily supply the appropriate filters, using the same manufacturing and calibration protocols used when producing optical reference materials for companies and standardisation bodies in the UK, USA and many other countries.
This included calibration to the exacting standards of Ukas, the UK Accreditation Service.
Starna Scientific has the skills and technology to produce filters and windows in a variety of shapes and sizes, in many different materials including glass, quartz, sodium chloride, and potassium bromide.
In addition it has in-house coating facilities producing a wide range of reflective metal, anti-reflection and multi-layer coatings.
