The ARCspectro VIS-NIR DR combines two spectrometers: a standard multichannel grating spectrometer that covers the visible spectral range (360nm-950nm) and the Arcoptix NIR scanning Fourier-transform spectrometer with an extended range InGaAs detector which is sensitive in the NIR range from 900 to 2500 nm. Both spectrometers are connected to a 5 cm integrating sphere. The sample is illuminated with perfectly diffuse light thanks to the integrating sphere including a high power halogen lamp.

The ARCspectro VIS-NIR DR allows you to measure the reflectivity of materials and paints over the complete solar spectral range - from 360 to 2500nm. This is important for the painting, building or solar energy industries, because it provides crucial information about the solar energy absorbed and transformed into heat by those materials or paints.

Those charateristics make it an ideal tool for measuring the Total Solar Reflectance (TSR) according to the ASTM ® norms G173 and E903. The software included with the VIS-NIR DR automatically calculates the TSR value. The ArcSpectro VIS-NIR DR complete measurement system is proposed for a very competitive price. This offers an interesting alternative to other commercially available spectrophotometers which may be more versatile but are also slower, more complex, and much more costly.

Features	VIS-NIR DR
Spectrometer type	Multi-channel grating spectrometer (360-950nm) & scanning FT-NIR spectrometer (900-2500nm)
Spectral range	360nm-2500nm
Spectral resolution	5nm (optical, reporting interval: 1nm)
Measurement geometry	Diffuse illumination and 8° viewing
Integrating sphere internal diameter	50mm
Measurement port diameter	10mm
Light source	Halogen, 5W
Measurement time	~5s
SNR (Full dynamic range-signle measurement)	>1'000:1
Inter-instrument agreement	±1% at 50% R
Read Repeatability On White Ref	Less than 0.2% variation at 50% R
Inter-instrument agreement for Reflectance (CIELAB)	Better than 0.2
Operating temperature	10°C-40°C
Operating power	12V / 15W (line power adaptor is included)
Communication Interface	USB
Software interface	Windows 7 / 10
Product dimensions	38mm x 25cm x 32cm
Product weight	8 kg

Lowering our need for energy and reducing our carbon footprint are crucial objectives for our future. Houses must be as energetically autonomouns as possible, which has to be achieved with a well engineered energy balance, and good thermal insulation. Solar radiation participates to this energy balance. In some situations, such as in cold countries, one may want the solar radiation to be absorbed as much as possible to help heating the building. In warm countries, converesely, a highly reflective surface is preferable.

However, is the a reflectivity measurement in the visible range of the solar spectrum sufficient to asses the overall reflectivity of a surface?

 

As illustrated in the graph below, more than half of the enegy of the solar spectrum lies in the near-infrared (NIR) between 700 and 2500nm. This radiation participates to the heating, and must therefore be taken into account.

In order to give a standard comparison between the reflectivity of different surfaces, that takes into account the whole solar spectrum, a standard parameter called Total Solar Reflectance (TSR) has been introduced. Essentially, the TSR is a reflectivity ponderated by a standardized solar spectrum (see ASTM ® norms G173 and E903):

The following figure illustrates the VIS-NIR reflectivity spectrum of two different paints. Their reflectivity of both paints is the same in the visible range, but it is considerably different in the NIR range. Hence, although these two paints would look identical to the human eye, one of them will absorb more solar radiation than the other.

The ARCspectro VIS-NIR was expressely developed to measure the TSR. It does cover the whole spectral range from 360 to 2500nm, and it is a fast, reliable, easy to use and comparatively low-priced instrument.

Here is a selection of articles discussing this topic more in details:

• Article from BASF (Link)
• Article from Chromaflo Technologies (Link)

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