BTS256-EF – mobile light meter for photopic and scotopic illuminance, EVE factor, luminous color, color rendering index, luminous spectrum and flicker.
The BTS256-EF is a high-quality light meter that is well suited for illuminance and luminous color measurements in all application areas thanks to its compact design, high-quality light sensor and precise cosine field of view function. Another special feature of the device is its ability to perform flicker measurements.
BiTec light sensor for precise light measurements
One of the outstanding properties of this mobile light meter is its BiTec light sensor. This combines the characteristic properties of a silicon photodiode with those of a noise-free CMOS diode array. The BiTec sensor guarantees extremely precise photometric and spectral-radiometric measurement values over a large dynamic range through mutual correction of the measurement signals of both sensors.
Silicon photodiode detector, fast and linear
When taking into account the dynamic range, linearity and speed, silicon photodiodes have always been and are still the ultimate radiation detectors. A silicon photodiode is therefore integrated in the BiTec light sensor of the BTS256-EF light meter. Its matching to the photometric V(λ) responsivity is improved by correction with the spectral measurement data of the diode array. The photodiode is be used to determine the frequency of modulated light and thus evaluate the flicker risk.
Flicker measurement entails identification of a possible AC component of the light signal with a 5kHz bandwidth. Besides the flicker frequency, other flicker parameters i.e. Flicker percent and flicker index are also displayed. The device additionally performs a Fast Fourier Transformation so as to display other frequency components in the signal.
Diode array detector for spectral measurement data
The CMOS diode array of the BiTec Light sensor provides precise measurement data required for the luminous spectrum. This data is then used for calculation of the color values and scotopic illuminance as well as for optimization of the photometric responsivity.
Optimized Signal to Noise Ratio
The noise signal from diode array detectors has significant effect on the signal to noise ratio (SNR) and hence on the quality of the measurement signal as well. A remote controlled aperture in the BiTec light sensor enables online compensation of the dark signals that are dependent on the temperature and integration time.
Pulse Width Modulated (PWM) LED lamps
The fast photodiode of the BiTec light sensor enables the BTS256-EF to automatically synchronize itself to the frequency of lamps operated in PWM mode.
Precise cosine corrected field of view
A cosine corrected field of view is absolutely necessary for illuminance measurement devices. For extended illuminance setups, the cosine goodness-of-fit has significant influence on the measurement uncertainty of the light meter. The BTS256-EF light meter is equipped with a diffuser window that has a 20mm diameter whose cosine matching ensures an f2 ≤ 3% uncertainty which corresponds to the DIN 5036 requirements for the quality class B. Both detectors of the BiTec light sensor are centrally aligned behind the diffuser window and therefore have the same view angle.
DIN quality class A and B luxmeter
Through the cutting-edge Bi-Technology sensor concept, use of modern electronics, online dark signal adjustment and the possibility to perform temperature compensation, the device meets the conditions specified for two of the DIN 5036 quality classes.
- In terms of the f2 uncertainty i.e. ≤ 3%, the device corresponds to the quality class B (DIN 5032 section 7).
- In applications where limitation of the viewing angle is acceptable, the BTS256-E, with its f1’, u, f3 and f4 values, corresponds to the quality class A (DIN 5032 section 7).
Diverse photometric and colorimetric measurands by BTS256-EF
A much broader diversity of measurands as the one offered by conventional light meters is required for verification and testing of LED lamps. The BTS256-E offers fourteen measurands and thereby meets all the requirements for a modern light meter:
- Ep photopic illuminance
- Es scotopic illuminance
- Es/Ep ratio of night and daylight vision
- EVE “Equivalent Visual Efficiency” factor
- Ee irradiance
- Eλ spectral irradiance
- x, y CIE 1931 color coordinates
- u‘, v‘ CIE 1976 color coordinates
- CT color temperature
- Δuv Deviation from the blackbody locus
- λdom dominant wavelength
- λp peak intensity wavelength
- λ0,5 spectral half-width
- Purity color purity
- CRI Ra and R1 to R15 Color Rendering Index
Display modes for standard measurements
The BTS256-EF Bi-Tec sensor luxmeter has several display modes where the necessary measurands for the common photometric measurements are incorporated. The cursor buttons can be used to switch between the displays.
User display modes
The BTS256-EF enables users to individually configure and save display modes. The required measurands can hereby be selected.
Info display for measurement parameters
An incorporated Info Display shows all the relevant measurement parameters.
Easy operation and handling
Three control buttons and the diligently structured menu navigation make the device easy and safe to operate the device. For instance, in the standard measurement mode, the user does not have to manually set the measurement parameters since these are automatically and perfectly adjusted to match the measurement conditions. In the expert mode, the user has access to all measurement parameters.
Many useful extra functions
- If the user wants to distance himself from the device’s field of view, he/she can set a time-delayed measurement.
- The display can automatically be dimmed during the measurement.
- An acoustic signal can be set to mark the end of a measurement.
- A layout created using a PC with the support points for the single measurements can be adopted in the device for measurement of the illuminance distribution. The measurement points can be progressively processed and saved.
- Fast data logger measurement mode where time-clocked readings of the photodiode can be recorded at a maximum measurement rate of up to 100ms.
- A second data logger measurement mode that enables time-clocked recording of all measurands including the spectral measurement data.
- Date and time in real-time can also be set.
The measurement device has a tripod stand socket on the bottom side.
Protective cap with chain
The protective cap for the diffuser window is attached onto the device.
Use without PC
The BTS256-EF has all the necessary functions enabling free operation of the device without having to depend on a computer. Furthermore, the rechargeable batteries have a capacity of more than 8 operation hours. The USB power adapter enables recharging of the device without a PC.
Use with PC
The BTS256-E additionally has a USB2 interface for use with a PC. This enables both data exchange and battery charging.
The S-BTS256-E software included in the device’s price provides all the necessary functions for the measurements, measurement data display and data transfer. The cutting-edge, flexible desktop concept of the software offers the user an individual constellation of the required measurement values. This can be a full screen filled with lux measurement values or a matrix with both numerical and graphical fields. Each desktop constellation can easily be saved for future use.
Software Development Kit
Gigahertz-Optik offers programmers the S-SDK-BTS256-E Software Development Tool. This can be used with LabView from National Instruments, .NET from Microsoft and C/C++. The SDKs simplify integration of the BTS256-E in an internally developed software.