Measurement for our planet
Measurement for our planet

As COP26 approaches, discover how NPL plays a key role in enabling climate action through the delivery of accurate, reliable data that supports decision making and enables low carbon innovation.

Measuring transmittance in the ultraviolet, visible and near-infrared (UV-vis-NIR) range

Regular transmittance

We provide regular transmittance measurements from 200 nm to 3000 nm, at either selected wavelengths or by using a scanning technique at regular intervals. Wavelength intervals are typically 5 nm and can be as low as 0.05 nm. Small wavelength interval scans are most useful when measuring wavelength standards that have narrow absorption bands. The spectral bandwidth used for wavelengths up to 800 nm is chosen by the customer and can be up to 5.0 nm. Above 800 nm, the bandwidth usually varies with wavelength up to a maximum of 20.0 nm. Typical measurement uncertainty for a 90% transmitting filter in the visible part of the spectrum is ± 0.2%. Uncertainties for other transmittance values or wavelengths depend on the filter characteristics.

Solar integrated values

Solar integrated values of transmittance can be calculated using Parry Moon air mass 0, 1 and 2, or Makarova air mass 0 solar data.

Wavelength and bandwidth (transmissive evaluation)

For narrow bandpass filters, we can provide calibrations of the wavelength of the transmittance / absorption peak, as well as other data such as the half height bandwidth, centre wavelength and wavelength of centre of gravity of peak.

Don’t see what you are looking for? Our diverse skill set enables us to provide bespoke solutions. Please contact us to discuss your requirements.

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Contact our Customer Services team on +44 20 8943 7070