Purpose

This Reference Material can be used to qualify the Absorbance scale, in the ultra-violet, visible and near-infrared regions of the spectrum (250 nm to 3200 nm) of spectrophotometers with spectral bandwidths not exceeding 6.5 nm.

Description and Discussion

The transmission characteristics of the filter are determinedby the thickness of a metallic coating deposited on a quartz plate. The metallic surface is overlaid by an optically bonded cover plate, to protect it from oxidation, contamination, or physical degradation. We consider the bonded cover plate to be more durable than the overcoating method employed by other suppliers.

The filters are mounted in stress-free black-anodizedaluminium alloy holders, with front and rear sliding coversthat protect the filters when not in use. All individual references and sets are supplied with an empty filter holderfor use as a measurement reference.

The spectrum of these filters is essentially flat from 250 nm to 3200 nm. Absorbance and Transmittance values are certified at 250.0,360.0, 465.0, 546.1, 635, 1100, 1700, 2210, 2500, and 2850 nm.

These filters are based on a NIST SRM series whose values follow a sequence of Transmission rather than Absorbance values. Approximate values available are: 92 %T (0.04 A), 50 %T (0.3 A), 30 %T (0.5 A), 10 %T (1.0 A), 3 %T (1.5 A) and 1 %T (2.0 A)

Instruments to be qualified should have a bandwidth of 5nm or less.

Note: The measurement values given in this document are for guidance only. The Calibration Certificate accompanyingthe Reference Material gives the actual values measured at a bandwidth of 1 nm.

As these filters attenuate the incident radiation partly by reflection, inter-reflections could be generated withinthe sample compartments of some spectrophotometers. This could affect the accuracy of measurements, and it is recommended that potential purchasers contact the manufacturer of their instrument to check its compatibilitywith metal-on-quartz filters.

Typical spectra

NIR-Metal-on-Quartz

 

Catalogue Number

They are available in sets:

  Catalogue Number 

Metal on Quartz NIR Reference Set:
3 & 50 %T (1.5 & 0.3 A) & Blank Holder

RM-NQ35NQ 

Metal on Quartz NIR Reference Set:
10, 30 & 90 %T (1.0, 0.5 & 0.04 A) &Blank Holder

RM-1NQ3NQ9NQ

Metal on Quartz NIR Reference Set:
1, 3 & 50 %T (2.0, 1.5 & 0.3 A) & BlankHolder

RM-NQ1NQ35NQ

 

Or as individual filters:

Nominal Values

Catalogue Number

% Transmittance

Absorbance

92

0.04

RM-9NQ

50

0.3

RM-5NQ

30

0.5

RM-3NQ 

10

1.0

RM-1NQ

3

1.5

RM-NQ3

1

2.0

RM-NQ1

Any combination of filters can be ordered as a set by combining the catalogue numbers as in the examples above. A blank filter holderis supplied with each reference or set of references.