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Mobile UV spectroradiometer for irradiance and dose for intensive radiation sources in the wavelength range from 200 nm to 525 nm.


Typical applications for high-intensity radiation sources in the ultraviolet and blue spectral range are UV radiation curing, solar simulation, UV sterilization, UV test systems, and UV sewer rehabilitation. For process-based applications with repetitive measurement tasks, broadband radiometers such as the X11 with RCH-116-4 are generally the most effective solution because of their ease of use, value for money, and low re-calibration cost.

Spectroradiometers such as the BTS256-UV are an alternative to broadband radiometers that provide additional information about the spectral distribution of radiation sources. The spectral information is particularly important if the wavelength-dependent aging behavior of broadband UV lamps must be investigated or if the irradiance must be measured in different wavelength ranges. This is also important if sources of differing spectral distribution must be measured. For this purpose, broadband radiometers ideally require separate calibration factors that take these spectral differences into account. This is not necessary with spectroradiometers. In addition, spectroradiometers offer more precise measured values than broadband radiometers. This is due to their spectral sensitivity function which corresponds to a rectangular function in the selected spectral measuring range. For precise measurements in the UV spectral range, very good stray-light rejection is necessary, which is not provided by the array spectrometers typically available on the market.

BTS256-UV spectroradiometers comply with the latest design criteria for radiometric measuring instruments in the field of optical radiation


Short descriptionSpectroradiometer for irradiance and dose of intense UV radiation in the wavelength range 200 nm to 525 nm.
Main features12 mm height. Stainless steel housing enables high temperature operation and intense UV radiation measurement. Electromechanical aperture for offset compensation. Internal stray light suppression. Traceable calibration.
Measurement rangeup to 40,000 mW/cm² , 200 nm to 525 nm.
typical applicationsMeasurement device for process control in UV curing applications both as a process flow meter as well as a mobile handheld measurement device, UV accelerated ageing of drugs, use inside environmental chambers with UV light sources.
CalibrationFactory calibration, traceable to international standards.
SensorBi-technology sensor with a broadband sensor and an array spectroradiometer. Integrated aperture for automatic dark adjustment.


Input opticsdifferent input optics. For example diffuser with 10 mm diameter directly on the device or diffuser with 9 mm diameter on heat-resistant rod.
Spectral Detector
ChipCMOS detector
spectral range(200 – 525) nm
Optical Bandwidth2.8 nm
Data Resolution0.1 nm
Integration Time(5.2 – 30000) ms
ShutterAutomatic aperture for dark signal measurements with the same integration time as the integration time of the measurement. In addition, stray light correction by means of built-in color filter (OoR correction).
Aperture delay = 100ms.
Peak wavelength+/- 0.3 nm
typical measurement timeBTS256-UV-2 and BTS256-UV-3:

typical 360 nm LED with 50 mW/cm² – 65 ms

typical 460 nm LED with 50 mW/cm² – 35 ms



typical 360 nm LED with 50 mW/cm² – 100 ms

typical 460 nm LED with 50 mW/cm² – 45 ms

Integral Detector
Measurement time(0.1 – 6000) ms
temperature rangeThe measured values of the diode are corrected by means of an internal temperature sensor.
FilterMathematical adjustment of the responsivity to a rectangular function from 250 nm to 450 nm (SMCF correction). *


* The spectral responsitivity of the diode does not correspond to a rectangular function (not possible with optical filters). When measuring light sources with a spectrum that deviates from the calibration spectrum of the integral detector (UV LED, peak at 405 nm), the measurement result is corrected using SMCF. The uncertainty of this correction depends on the quality of the measured spectrum (noise) and the size of the correction factor (spectral range). To correctly calculate the SMCF, the entire spectrum of the radiator to be measured must be measured. If the emitter has radiation outside the spectral sensitivity range of the measuring device, this increases the uncertainty of the SMCF.

typical irradianceBlue LED with Peak @405 nm: (2E-3 – 2E3) W/m²
spectral responsivitytypical spectral responsivity BTS256-UV-1 (standard calibration 225 nm to 525 nm):

typical spectral responsivity BTS256-UV-2 and BTS256-UV-3 (standard calibration 200 nm to 525 nm):

Microprocessor16Bit, 25 ns command cycle time
Power Supply5 VDC, 450 mA by USB
InterfaceUSB 2.0 (type mini USB)



Weight275 g
Dimensionsbasic body BTS256-UV-1 und BTS256-UV-3: 148 mm x 92 mm x 13 mm (Länge x Breite x Höhe)

basic body BTS256-UV-2: 148 mm x 92 mm x 12 mm (Länge x Breite x Höhe)

Logger memory100 samples (spectral data), 10000 samples (diode)
temperature rangeOperation: +10°C bis +30°C (The temperature at the measuring head can be higher for a short time)

Storage: -10°C bis +50°C


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