Some light measurement applications require the light sensor to be installed within a measurement system or operated remotely. Industrial applications often require integration with PLC systems. Continuous and remote operation requires light measurement sensors to be robust. For such tasks, Gigahertz-Optik offers the compact spectral light sensor CSS-45. It is a precise spectroradiometer covering the wavelength range 360 nm to 830 nm.
Spectroradiometer sensor with outstanding light measurement characteristics
- Individual wavelength and linearity correction guarantee precise measurements of light sources irrespective of intensity and spectral distribution.
- Mathematical bandwidth correction according to CIE 214 for accurate colorimetric measurements.
- Another unique feature of the CSS-45 is its electromechanical shutter which enables the remote-controlled dark adjustment of the sensor. This is essential for temperature-independent and long-term operation of array spectrometers.
- Diffuser with a precise cosine adjustment (f2 ≤ 1.5 %) for measuring the illuminance and irradiance of extended light sources and lighting equipment.
- Wide range of illuminance measurement from 1 lx to 350.000 lx, covering applications from emergency lighting to broad daylight conditions.
Robust and compact
The compact metal housing features an M6 threaded hole and a V-groove around the device for universal attachment of the CSS-45. The dimensions are given in the technical drawing available for download. The housing with its splash-proof electrical connectors meets the requirements of protection class IP62. For IP65 rated protection, a sensor variant with glass dome is required.
Interfaces and Software
The sensor offers both an RS-485 and a USB interface for remote operation. The addressable RS-485 interface allows very long supply lines. Multiple CSS-45 sensors can be operated together under RS-485 control as well as in USB remote operation. In addition to the provided end-user software, a software development kit (SDK) is optionally available for simplified integration of the sensor into user written software.

Schematic draft of CSS-45 sensor
1) Incident light 2) Cosine diffuser 3) electromechanical shutter 4) array spectrometer 5) CPU 6) temperature sensor 7) USB connector 8) RS-485 connector 9) V-groove 10) M6 mounting thread
Numerous metrics for a wide field of measurement applications
The CSS-45 includes an integrated processor. It calculates a comprehensive set of radiometric, photometric and colorimetric quantities from the measured spectral measurement data.
Additional metrics support further applications:
- Horticultural lighting – PAR measurement Photosynthetic Photon Flux Density (PPFD) in μmol/m²s
- Human Centric Lighting – melanopic irradiance and illuminance (CIE S 026:2018), melanopic daylight equivalent illuminance
- Phototherapy – total irradiance for bilirubin, Ebi, in mW/cm2 (IEC 60601-2-50) as well as average spectral irradiance in μW/cm2/nm (American Academy of Pediatrics)
Accessories
- The light sensor CSS-45 can be combined with the control unit CSS-D in order to be used as a handheld light meter.
Traceable factory calibration


CSS-45 cosine field of view.



Use of CSS-45 as a handheld instrument by combining it with the control unit CSS-D
General | |||
Short description | Remote spectroradiometric detector for universal use in radiometric and photometric measurement setups. |
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Main features | Remote operation via USB 2.0 or RS 485. Compact, robust, splashproof housing with universal mounting options. Direct output of radiometric, photometric, colorimetric and specialist functions. Precision cosine diffuser. Remote controlled dark level shutter. Application software. |
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Measurement range | 1 lx to 350,000 lx (for white LED), 360 nm to 830 nm. |
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typical applications | Photometric and radiometric setups requiring remote positioning of single or multiple detectors. Use with positioning equipment e.g.for mapping. Industrial monitoring, grow lights, blue light phototherapy, human centric lighting. |
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Calibration | Factory calibration. Traceable to international calibration standards. |
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Product | |||
Input optics | Diffuser window with 10 mm diameter, cosine corrected field of view, f2 ≤ 1.5 % |
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Measured Quantity | Illuminance photopic |
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CSS-45 | Detector head for illuminance and light color. (Class B according DIN 5032-7 or AA according to JIS C 1609-1:2006) |
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Spectral Detector | |||
spectral range | (360 - 830) nm |
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Optical Bandwidth | 10 nm optical bandwidth correction applied according to CIE 214
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Measurement range typ. white LED | (1 - 350,000) lx |
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Repeatability Δx and Δy | ± 0.0002 |
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Δy Δx uncertainty | ± 0.002 (Standard illuminant A) |
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CCT Measurement range | (1700 - 17000) K |
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ΔCCT | ± 50 K (standard illuminant type A) ± 4 % (depending on the LED spectrum) |
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Calibration | |||
Calibration uncertainty | Illuminance (standard illuminant A) ± 3 % Illuminance (typ. LED) ± 4 % (Traceable to national standard. Uncertainty of the standard is included) |
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Miscellaneous | |||
Interface | USB 2.0, RS 485 |
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temperature range | Operation: 10°C to +30°C Storage: -10°C to +50°C |
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Power Supply | 5 VDC by USB (3.5 - 25) VDC by custom plug max. current 500 mA |
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Weight | 130 g, only sensor without cables |
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Dimensions | 45 mm diameter 53 mm height*
* height without WT protection dome
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Housing | Splashproof/Watertight class: CSS-45: IP62 CSS-45-WT: IP65 |
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