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Nominated for the Innovation Award Bavaria 2018

BTS2048-UV-S fast BiTec sensor spectroradiometer for high-quality UV measurements

The BTS2048-UV-S is a high-quality spectralradiometer whose compact design and elaborate optical, electronic and mechanical interfaces make it ideal for integration in complex industrial and scientific measurement tasks.

BiTec sensor for high-end light measurement 

One of the outstanding features of this exceptional spectroradiometer is its BiTec sensor. This combines the special properties of a photodiode with those of a back-thinned CCD diode array. Through bilateral correction of measurement signals from both sensors, the BiTec sensor ensures precise radiometric and spectral-radiometric measurement values over a large dynamic range.

High-quality back-thinned CCD detector 

The diode array comprising of 2048 pixels has a utilizable spectral responsivity range between 190 nm and 430 nm. It has a 0.7 nm optical bandwidth and a pixel resolution of 0.13nm/pixel. Due to the back-thinned technology, this CCD chip is substantially more sensitive as compared to conventional front-illuminated CCD chips. Furthermore the CCD is one stage cooled (1TEC).

Flash spectral radiometer 

Another of its features is that the back-thinned CCD detector is equipped with an electronic shutter. This makes the measurement within a light flash possible. Together with the diverse trigger functions, integration times of between 2µs and 60000ms, the powerful micro-processor and the very fast LAN interface (7ms for a complete data file), the BTS2048-UV-S qualifies for a wide range of applications.

Precise spectral radiometry (low straylight)

To facilitate optimum use of the CCD sensor‘s dynamic range and to overcome the problems of most array spectoradiometers in the UV range, there is a remote controlled filter wheel (Open, Closed, optical filters) located in the optical beam path. This filters combined with smart measurement and stray light correction routines enables high quality measurements of the BTS2048-UV-S. Results are compareable with double monochromator results (see figure). However the measurements time is significantly lower. Since for the BTS2048-UV-S a filter wheel with 8 filter positions is implemented a furhter smart measurement routine for stray light reduction is implemented compared to the BTS2048-UV.

Diffuser window instead light guide 

As for the input optics, the BTS2048-UV-S has an incorporated diffuser window with a cosine corrected field of view. The fact that a light guide has not been used improves sensitivity and calibration stability. The f2 adjustment of the cosine corrected field of view to less than 3% makes it possible to use the BTS2048-UV-S for direct measurement in absolute radiometric measurands

  • Irradiance (W/m²)
  • Spectral irradiance (W/(m² nm))
  • Radiant intensity (W/sr)
  • Spectral radiant intensity (W/sr nm)

Radiant power measurement 

In connection with integrating spheres, the BTS2048-UV-S is the optimal light meter for measurement of the radiant power respectively spectral radiant power. The prefixed diffuser window can be positioned in the sphere such that an uninterrupted hemispherical field of view is created. Gigahertz-Optik manufactures a wide range of integrating spheres as well as the necessary accessories e.g. calibration standards.

Ultra fast interfaces 

The BTS2048-UV-S is controlled via a USB 2.0 or Ethernet interface. With regards to the communication speed the ethernet port is superior to the USB2.0 interface. Furthermore, the data preparation occurs in the BTS2048-UV-S to optimize the datatransfer speed. For this purpose, an independent, high-performance microprocessor is incorporated.

User software with flexible desktop structure 

Among the BTS2048-UV-S delivery contents is the S-BTS2048 user software. One of the characteristic features it has to offer is the flexible desktop that can be individually configured by the user. This entails a potpourri from which the user can choose graphical and numerical display windows:

  • Freely definable numerical displays in decimal or scientific representation. Zoom function.
  • Numerical display fields for radiometric, spectral and other measurands.
  • Measurement protocol of the selected measurement parameters.
  • CIE 1931 chromaticity diagram. Zoom function.
  • Spectrum. Zoom function.
  • Data logger. Zoom function.
  • etc.

Traceable calibration 

Calibration of the BTS2048-UV-S, including its accessories, is performed by Gigahertz-Optik calibration laboratory for optical measurands with reference to national and international calibration standards. 


Comparison of a solar measurement of the BTS2048-UV-S and a standard double monochromator. The BTS2048-UV-S achieves about the same quality in a measurement time of a few s compared to about 1.5 min of the double monochromator.
Electronic Shutter reduces the measurement time
Ethernet interface reduces the datatransfer time
S-BTS2048 software for the BTS2048-UV-S
The BTS2048-UV can directly plugged on a integrating sphere (picture shows the constructional identical BTS2048-VL)
typical applications

Lightmeter for spectral Irradiance, Erythema, etc.

Measured Quantity

Spectral irradiance (W/(m² nm)), irradiance (W/m²), peak wavelength, center wavelength, centroid wavelength, Erythema. Option integrating sphere: in addition spectral radiant power (W/nm) and radiant power (W)

Input optics

Diffusor, cosine corrected field of view (f2 ≤ 3 %)

Filter wheel

8 positions (open, closed, optical filters). Use for remote dark current measurement and stray light reduction.


Parallel measurement with diode and array is possible, thereby linearity correction of the array through the diode and online correction of the spectral mismatch of the diode through a*(sz(λ)) respectively F*(sz(λ)).

Calibration uncertainty

Spectral irradiance

(200 - 249) nm: ± 12 %
(250 - 339) nm: ± 7 %
(340 - 399) nm: ± 5 %
(400 - 430) nm: ± 4 %

Spectral irradiance responsivity (200 - 430) nm

Spectral Detector
Integration Time

2 μs - 60 s        *1

spectral range

(190 - 430) nm

Optical Bandwidth

0.8 nm

Pixel resolution

~0.13 nm/Pixel

Number of pixels



Highly sensitive back-thinned CCD chip, one stage cooled (1TEC)


16bit (25 ns instruction cycle time)

Peak wavelength

± 0.05 nm

Band-pass correction

mathematical online band-pass correction is supported


completely linearized chip >99.6%

Stray Light

Out of Bound method < 1E-4           *3

Bandpass method < 1E-5           *3

Base line noise

5 cts     *4


5000        *5

dynamic range

>9 Magnitudes

spectral irradiance responsivity range

(3E-5 - 3E4) W/(m²nm) @325nm        *6*7

typical measurement time

W/m² of a Halogen lampe from (250 - 400) nm

1 4,4 s
10 440 ms
100 44 ms
Measurement modes

Standard measurement mode: 200 nm to 430 nm

Out of Range stray light corrected measurement mode (OoR SLC): 200 nm to 430 nm

Stray light corrected bandpass mode for solar measurements (solar BP SLC): 285 nm to 420 nm

Universal stray light corrected bandpass measurement mode (BP SLC): 245 nm to 420 nm

Integral Detector

Mathematical adjustment of the responsivity to a rectangular function from 220 nm to 360 nm (SMCF on-line correction to the radiometric function with the measured spectral data).*

* 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).

Measurement time

(0.1 - 6000) ms

Measurement range

seven (7) measurement ranges with transcendent offset correction


Irradiance ± 6 %               *10

Measurement range

(5E-3  -  2E5) W/m²       *11


spectral responsivity

responsivity BTS2048 UV

f2 (directional response/cosine error)

cos BTS2048 VL3


32bit for device control,16bit for CCD array control, 8bit for photodiode control


USB V2.0, Ethernet (LAN UDP protocol), RS232, RS485

Data transfer

Standard for 2048 float array values via ethernet 7ms, via USB 2.0 140 ms

Input Interfaces

2x (0 - 25) VDC, 1x optocoupler isolated 5 V / 5 mA

Output Interfaces

2x open collector, max. 25 V, max. 500 mA


Trigger input incorporated (different options, rising/falling edge, delayed, etc.)


User software S-BTS2048
Optional software development kit S-SDK-BTS2048 for user software set-ups based on .dll‘s in C, C++,C# or in LabView.

Power Supply

With power supply: DC Input 5V (±10 %) at 700 mA
With USB bus (500mA) *8


103 mm x 107 mm x 52 mm (Length x Width x Height)


500 g


Tripod and M6 screw threads

Front adapter UMPA-1.0-HL for use with integrating sphere port-frame UMPF-1.0-HL

temperature range

Storage: (-10 to 50) °C

Operation: (10 to 30) °C           *9

temperature range

CCD Chip: ≤ ± 0.25 °C


*1 It is recommended to perform a new dark signal measurement for every change in the integration time

*2 typical value, the uncertainty of the dominant wavelength depends on the spectral distribution of the LED

*3 typical value, measured 100 nm left of the peak of a cold white broadband LED with and deep blue LED peak

*4 *5 typical value measured without averaging for a 4ms measurement time and full scale control of the array. Averaging results in quadratic rise of the S/N
i.e. quadratic fall of the base noise e.g. averaging to a factor 100 improves the S/N by a factor 10

*6 Minimum 500/1 S/N. Maximum at full scale control.

*7 Irradiation only allowed for a short time so as to avoid thermal damage

*8 during USB connection, not all functions are available due to the limited current supply e.g. no Ethernet and TEC cooling

*9 Device required for temperature stabilization in approx. 25min. In measurement is performed in the warm-up phase, or if measurements are performed
under varying temperatures, dark signal measurement is required for each measurement

*10 With a(Z) correction by a Deuterium lamp

*11 By a spectral power distribution of a deuterium lamp, maximum radiation only allowed for a short time so as to avoid thermal damage

Option: 80mm Integrating Sphere (UMBB-80)
spectral responsivity

spectral responsivty sphere 80 mm BTS2048 UV S

Type Description File-Type Download
Datasheet BTS2048-UV-S PDF
BTS2048-Series BTS2048 'Not just another spectrometer' brochure PDF
Produktname Product Image Description Show product
S-BTS2048 Application software for BTS2048 variants.
S-SDK-BTS2048 Software Development Kit for BTS2048 variants.
Article-Nr Modell Description Request / Compare
15298727 BTS2048-UV-S

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

15300809 K-BTS2048-UV-S

Recalibration of the BTS2048-UV-S with calibration certificate

15298474 S-BTS2048

User software for BTS2048 and variants.

15298470 S-SDK-BTS2048

Software development kit with users guide.

15307925 S-T-RECAL-BTS2048

Software module for functional enhancement of S-BTS2048 software. Support of BTS2048 series light meter re-calibration via the user.

15312474 BTS2048-Z03

Trigger cable. For use with LPS-20 power supply.

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