CL2 Spectral Irradiance Standard

CL2 spectral irradiance standard

The CL2 is a universal spectral irradiance standard lamp for the calibration of spectroradiometers, lux meters and radiometers. Its mounting bracket is compatible with all optical table and mounting systems. Calibration distance is measured from a simple datum face plate.

The calibration is performed with respect to National Physical Laboratory (NPL Teddington UK) calibrated lamps held by Bentham. Alternatively, direct NPL calibration can be offered.


Measurement type Spectral irradiance at 0.5m distance from datum face
Wavelength range 250-3000nm, 5nm intervals
Peak spectral irradiance 30mW/m2.nm at 800nm
Integrated irradiance 7383 (mW/m2)
Illuminance 1200 lux
Chromaticity coordinates, CIE 1931 & 1976 x = 0.425, y = 0.400

u' = 0.245, v' = 0.520
Correlated colour temperature 3200 K

The CL2 is usually supplied with a 100W quartz halogen lamp. It requires a precision constant current dc power supply at 8.5A.

The CL2 can be supplied with alternative lamps ranging from 10W to 250W. It can also be supplied with spectral radiant intensity calibration, mW/(sr.nm).

Bentham offers 2 variants of a 250W rated constant current p.s.u. for use with calibration lamps, models 605 and 608. The latter includes a current ramping facility for lamp switch on and off.

CL2 spectrum

Plane of Measurement

CL2 plane of measurement


Lamp Rating 10,50 and 250W lamps available
Calibration Ranges UV extension 250-300nm

IR extension 800-3000nm
Calibration Distance Calibration at 200mm from datum face
Alternative Variants CL2_RI Radiant Intensity Standard Calibration performed at one metre distance from plane of filament to provide calibration in radiant intensity ( )

CL2_2856K Illuminant A Calibration performed at reduced lamp current to obtain a CCT of 2856K, illuminance in lux reported