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Averaged LED intensity

In an attempt to bring some conformity to the data presented in LED manufacturers’ literature, the CIE introduced the new term  ‘Averaged LED Intensity ‘ For this purpose CIE 127 defines measurement distance and the area over which it is to be performed.  The commonly used ‘Condition-B’ specifies a measurement distance of 100mm and a sensor area of 100 mm² which must have extremely high uniformity over its entire area. The BTS2048-VL with the CP-ILED-B-IS-1.0-HL input lens is ideal for measurement of the “averaged LED intensity ILED-B”.

The BTS2048-VL light meter

The high-quality BTS2048-VL CCD based spectroradiometer is internationally recognized as a high-end product. It is one of the most compact spectroradiometers on the market which enables direct system integration in many applications without the need for the expensive, and potentially measurement degrading, light guides. Among its characteristic features a diffuser window which permits direct mounting onto integrating spheres for measuring luminous flux. More detailed information about the BTS2048-VL, which is also available with thermo-electric cooling in the BTS2048-VL-TEC version, can be found in the respective data sheets.

Use of the BTS2048-VL for front-end and back-end LED binning

The BTS2048-VL is ideally suited for use in industrial LED binning. In particular, it can be used to perform time-synchronized, pulsed measurements of LEDs as stipulated by CIE S025 or DIN 5032-9. This is necessary when one wants to account for thermal effects in measurements. The instantaneous, electronic zero setting of all pixels (electronic shutter) of the CCD sensor in conjunction with its trigger interface, results in perfect synchronization between the BTS2048-VL’s measurement and the LED current supply. The device has an exceptionally wide dynamic range with a minimum integration time of just 2 µs. This is 1000 times shorter than in conventional devices (typically milliseconds). Additionally, the internal OD1 and OD2 filters increase the dynamic range up to 9 orders of magnitude and the Ethernet interface provides rapid data transfer. For users to integrate the device into their system, the BTS2048-VL is supplied with the powerful S-SDK-BTS2048 software development kit that comes with a few helpful examples.

Expanding the BTS2048-VL to a luminous intensity spectroradiometer

Measurement of “averaged LED intensity” in accordance with CIE127 measurement geometry is common in LED binning. The BTS2048-VL can be combined and calibrated with the CP-ILED-B-IS-1.0-HL (ILED B) adapter for luminous intensity, spectrum, color, and color rendering index measurements using the standard CIE average LED intensity condition B geometry. Thanks to its compact design, light weight, and absence of a light guide, the adapter and spectroradiometer form a monolithic module that can be conveniently integrated into complete test systems for front-end and back-end LED binning. It is supplied as a fully calibrated module. The 2pi luminous flux spectroradiometer can be taken from the test system as a complete module for recalibration. Eliminating the need for connecting light guides enables convenient recalibration with low uncertainty.

The CP-ILED-B-IS-1.0-HL adapter for industrial LED binning

The CP-ILED-B-IS-1.0-HL is designed for measurement of the “averaged LED intensity” (ILED-B). Its 100 mm² detector area (11.28 mm diameter) is based on a compact integrating sphere with rugged synthetic coating which ensures the highest possible uniformity of responsivity over the entire reception surface. The integral tube adheres to the specified measurement distance of 100 mm and its inner surface is designed to minimise reflections. The output port of the sphere has an UMPF-1.0-HL connector for attachment to the BTS2048-VL.

Software for system integration

Gigahertz-Optik offers the S-SDK-BTS2048 software development kit for integration of the BTS2048-VL-CP-ILED-B-IS-1.0-HL luminous intensity spectroradiometer with the system software of the user’s LED test systems.


One essential quality feature of photometric devices is their precise and traceable calibration. The BTS2048- VL-CP-ILED-B-IS-1.0-HL is calibrated in Gigahertz-Optik’s DAkkS-accredited (D-K-15047-01-00) calibration laboratory. This accreditation is for the spectral responsivity and spectral irradiance of our laboratory in line with ISO/IEC 17025. Calibration is performed with the spot light source at a 100 mm distance from the reception surface. Every device is delivered with its respective calibration certificate.


The BTS2048-VL-CP-ILED-B-IS-1.0-HL luminous intensity spectroradiometer to measure Averaged LED intensity (CIE127 B) is a compact module that can be integrated in LED test systems.
S-BTS2048 user software
S-SDK-BTS2048 software development kit
Short description

Luminous intensity pectroradiometer as an integration module for LED test systems for front-end and back-end LED binning based on the luminous intensity (averaged LED intensity CIE127 B), spectrum, color, and color rendering index

Main features

Input optics according to CIE 127 B. High-quality CCD sensor spectroradiometer

Measurement range

ILED-B: Integral 0.15 mcd to 420 kcd.

Spectral for typical white LEDs:  15 mcd to 150000 kcd

Spectral radiant intensity: 2E-6 W/(sr nm) to 5E3 W/(sr nm)

Spectral range: 350 nm to 1050 nm

typical applications

Luminous intensity spectroradiometer for integration in LED test systems


Factory calibration. Traceable to international standards


better ± 1% within the active area of 1 cm²




tripod thread

BTS2048-VL with CP-ILED-B-IS-1.0-HL

Luminous intensity ILED-B: ± 4 %

Spectral Radiant intensity ILED-B:

(350 - 399) nm: OD0: ± 7 % OD1: ± 8 % OD2: ± 9 %
(400 - 800) nm: OD0: ± 4 % OD1: ± 4 % OD2: ± 4 %
(801 - 1000) nm: OD0: ± 6 % OD1: ± 6 % OD2: ± 6 %
(1001 - 1050) nm: OD0: ± 7 % OD1: ± 8 % OD2: ± 9 %

Spectral radiant intensity responsivity (350 - 1050) nm


spectral radiant intensity (ILED-B) responsivity range (spectral measurement): (5E-7 - 5E3) W/nm

measurement range ILED-B (integral measurement): (3E-4 - 1E6) cd

spectral range

(350 - 1050) nm

Optical Bandwidth

2 nm

Type Description File-Type Download
Datasheet BTS2048-VL-CP-ILED-B-IS-1.0-HL PDF
BTS2048-Series Brochure Not Just Another Spectrometer PDF
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15298833 CP-ILED-B-IS-1.0-HL

Adapter for the measurement of the Averaged LED Intensity following CIE 127 B regulation. Set-up with integrating sphere for best possible uniformity of the measurement area. Direct mount to measurement  instruments with UMPA-1.0-HL mount.

15298281 BTS2048-VL

Measuring device, hard cover box, users guide, software, calibration certificate.

15298687 BTS2048-VL-TEC

Measuring device, hard cover box, users guide, software, calibration certificate.

15300499 K-BTS2048-VL-I with ILED-B

Calibration of the luminous intensity responsivity of the BTS2048-VL with ILED adapter. Spectral range 350-1050nm. Calibration certificate.

15300769 K-BTS2048-VL-E

Calibration of the illuminance, irradiance responsivity and wavelength of the BTS2048-VL. Spectral range 350-1050nm. Calibration certificate.

15300499 K-BTS2048-VL-I with ILED

Calibration of the luminous intensity responsivity of the BTS2048-VL with ILED adapter. Spectral range 350-1050nm. Calibration certificate.

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