LUXIMETRO PORTATILE per misure Lux, CRI, T colore su Led e lampade

BTS256-E mobile light meter for photopic and scotopic illuminance, EVE factor,
luminous color, color rendering and luminous spectrum.

BTS256-E  Luxmeter mobile per illuminanza Fotopica e Scotopica, "Visual Efficiency” factor,
T° colore, CRI color rendering, spettro luminoso

Nuove tecnologie per misurare sul campo parametri luminosi

Come le lampadine a incandescenza stanno per essere sostituitie da nuovi progressi tecnologici, fotometri tradizionali e Luximetri devono aprire la strada a nuove tecniche di misura. La nuova tecnologia di misurazione deve essere idonea alle eccezionali caratteristiche di luci a LED e di altre lampadine a risparmio energetico, nonché essere in grado di eseguire il rendering del colore, la temperatura colore  e misure dello spettro luminoso, oltre alle misure di illuminamento.

14 differenti MISURE

Per misurare intensità luminosa, colore e spettro di emissione uno strumento deve possedere questi 14 parametri:
  • Ep photopic illuminance
  • Es scotopic illuminance
  • Es/Ep ratio of scotopic and photopic vision
  • EVE “equivalent Visual Efficiency” factor
  • Ee irradiance
  • Eλ spectral irradiance
  • x, y CIE 1931 color coordinate
  • u‘, v‘ CIE 1976 color coordinate
  • CT color temperature
  • Δuv deviation from the blackbody locus
  • λdom dominant wavelength
  • λp peak intensity wavelength
  • λ0,5 spectral half-width
  • CRI Ra and R1 to R15 color rendering index
Clear display of the measurement readings

In order to guarantee the user a constant comprehensive view of the measurement, the high resolution of the BTS256-E Bi-Tec sensor luxmeter‘s display enables the user to choose between 11 standard measurand configurations as well as five extra user displays that allow user customization. Switching between the different displays is done with the cursor buttons. An additional Info-Display shows the measurement parameter currently being used for the measurement

Accurate measurement data using the Bi-technology sensor

The BTS256-E light meter is equipped with a BTS256 Bi-technology light sensor from Gigahertz-Optik. The employment of two different light detectors blends in both of their characteristic features and hence helps avoid typical constraints. This cutting-edge technology allows, for the first time, the modeling of compact light meters whose measurement records match up to those of laboratory instruments.

Si-photodiode with photometric correction filter

The traditional light detector with silicon diodes and a photometric correction filter is, with regards to the dynamic range, linearity and speed, still the ultimate sensor. The only thing it lacks is the ability to perform color measurements and a perfect adjustment to the target function. This is why the Gigahertz Optik Bi-tech sensors are equipped with an extra diode array detector besides the classical semiconductor photodiode.

256 pixels diode array spectral radiometer

The BTS256 light sensor‘s CMOS diode array provides precise luminous spectrum measurement data. The spectral data is used for luminous value and scotopic illuminance calculations.

Automatic dark signal adjustment

A dark signal aperture in front of the photodiode and diode array is ideal for the dark signals dependent on the online compensation of the measurement time and hence enabling an optimum signal-to-noise ratio.

Bi-directional tuning of the measurement values

The measurement data from the two different detectors enables a mutual support. As a result, the photodiode‘s measurement values improve the linearity of the diode array whereas the diode array‘s measurement values lead to a better goodness-of-fit of the photodiode.

Modulated light measurement (PWM)

The fast photodiode additionally enables the necessary device synchronization while performing measurements of pulse width modulated (PWM) light.

The cosine adjusted field of view

The measurement geometry of the input optics has a huge influence on the quality of the measurement values. This should thus ensure a cosine corrected field of view that is as accurate as possible. Only then is the precise measurement of light from different angles of incidence, such as in general and street lighting, possible. Despite its large 20mm large diameter, the cosine adjustment of the BTS256-E corresponds to the DIN 5036 Quality Class B with f2 ≤ 3%.

DIN Quality Class B and A Luxmeter

Based on its cutting-edge bi-technology sensor concept, the use of the newest electronics, the online dark signal adjustment and the possibility of temperature compensation, the DIN 5036 Quality Classes evaluation criteria is not longer suited to the BTS256 concept. Taking the ≤ 3% f2 error into consideration, the BTS256-E corresponds to the Quality Class B (DIN 5032 part 7). In an application where the field of view is limited, the BTS256-E corresponds to the Quality Class A (DIN 5032 part 7) due to its f1, f3 and f4 values.

In addition to its high-quality technical properties, the BTS256-E offers many other useful functions and attributes that facilitate the extraordinary mobile use of the device.

Easy operation and handling

Thanks to 3 function keys and the diligently structured menu navigation, the device can easily and safely be operated. In the Standard measurement mode, the user is relieved from having to manually set up the corresponding measurement parameters as the device automatically adjusts itself depending on the measurement conditions. In the Expert measurement mode, the experienced user has access to the measurement parameters.

Many useful extra functions
  • If the user would like to get out of the field of view when performing the measurement, he can opt for the time delay measurement.
  • The display can be automatically switched off during the measurement.
  • If desired, the end of the measurement can be indicated using an acoustic signal.
  • In order to measure the illuminance distribution, a computer generated layout with the bases for the single measurements can be used with the device. The measurement points can be sequently executed and saved.
  • Fast data logger measurement mode, which allows clocked measurement values from the photodiode with a measurement rate of up to a maximum of 100ms.
  • A second data logger measurement mode that enables the clocked recording of all measurands including the spectral measurement data.
  • Date and time (real time clock) can be set.
Tripod mount

An integrated tripod socket is available underneath the device.

Attached protection cap

The protection cap for the measuring panel is attached on the device.

Use without PC

The BTS256-E is equipped with all the functions necessary for computer-independent use of the device. The rechargeable batteries have a capacity that can sustain the device for more than eight operation hours. The USB adapter can be used to recharge the battery even without having to use a PC.

Use with PC

The BTS256-E has a USB2 interface for its use with a PC. This enables both data exchange and battery recharging.

User software

The S-BTS256-E software offers all the functions necessary for the measurement, measurement data display and data transfer. The up-to-date, flexible desktop concept of the software offers the user an individual constellation of the required measurement values. This can either be just a full screen lux measurement values‘ display or a matrix containing the numerical and graphical display fields. Each desktop constellation can of course be saved for later use.

Software development kit

Gigahertz-Optik offers self-programmers the S-SDK-BTS256-E Software Development Tool. This can be used with Lab View from National Instruments, NET from Microsoft and C/C++. The SDKs simplify the incorporation of the BTS256-E in a self developed software.
Compact light meter for mobile use

Display with factory configuration

Display with user configuration

Ratio of scotopic and photopic illuminance with EVE factor (IES TM-24-13)

The protocol of the measurement parameters is also part of the data file with measurement data gespeichert

Socket for tripod mount

Hard-top case for safe transport and storage of the BTS256-E and its accessories

Standard display with Illuminance, x,y color coordinates, color temperature and emission spectrum of compact fluorescence lamp (CFL)

User software S-BTS256 with modular configurable desktop set-up

Graphic displays with zoom able size


Lightmeter DIN class B (DIN 5032 part 7)
DIN class A for f1’, u, f3 and f4 (DIN 5032 part 7)
Light sensor Bi-Technology Sensor with a photodiode broadband sensor and a 256 pixel CMOS diode-array. Integrated aperture for automatic dark signal adjustment.
Input optic Diffuser window with 20mm diameter, cosine corrected field of view, F2 Error ≤3%
Broadband Sensor Silicon photodiode with photometric correction filter f1≤6% (f1 A(z) korrigiert ≤3%). Transimpedance amplifier with adjustable integration time (from 100µs to 6s). Seven(7) measurement ranges with offset correction. 16 Bit ADC.
Maximum measurable illuminance value ≥199,999 lx
Noise equivalent illuminance value ≤ 0.01lx
Calibration uncertainty of photopic Illuminance +/-2.2%
Spectral Sensor CMOS diode-array spectral radiometer. Spectral range from 380 to 750nm. Pixel resolution 1.5nm. Optical resolution 10nm.
5.2ms to 30s integration time, manual or automatic control.
Automatic shutter for dark signal measurements with an integration time similar to that of the bright measurement. Shutter on/off response time 100ms
Measurement time by 199,999 lx ≤ 5ms (white light)
Measurement time by 100 lx ≤ 1s (white light)
Scotopic measurement range spectral 1 to >199999 lx
Calibration uncertainty of scotopic Illuminance +/-2.2%
Color measurement range spectral 1 to >199999 lx
Peak wavelength: +/- 1nm
Dominant wavelength: +/- 1nm
Δx, Δy reproduce: Standard illuminant A +/-0.0001, LEDs +/- 0.0002 at 2000cts peak output
Δx, Δy uncertainty : Standard illuminant A +/-0.002, LED +/- 0.004
CCT Measurement range: 1700 to 17000 K
ΔCCT: Standard illuminant A 50K; LED to +/- 4% depending on the LED Spectrum
Color rendering index Ra and R1 to R15
Microprocessor 16Bit, 25ns instruction cycle time
Charging voltage 5VDC, 450mA per USB
Interface USB2; Mini USB Port
Temperature Operation: -10 to +30°C, Storage: -10 to +50°C
160 x 85 x 60mm (LBH)
Transport case Plastic hard-top casing, 333 x 280 x 70mm, 650g


Ordering information

Model Item No.: Description
BTS256-E 102826 BTS256-E, Users guide (G or E), User Software S-BTS256 on CD, USB cable for use with PC and battery charging, USB power adapter (EU, USA or GB), BHO-17 Hard-top casing
S-SDK- BTS256-E 102777 Software Development Kit; Software and users guide on CD
K-BTS256-E-I 301374 Recalibration of the BTS256-E LED-Luxmeter


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