BTS256-E WiFi Light-Color-Spectral Meter

For photopic and scotopic illuminance, S/P Ratio, EVE factor, luminous color, color rendering index and light spectrum with WiFi interface

BTS256-E-LED Luxmeter for LED Measuremnt from Gigahertz-Optic

The BTS256-E WiFi Light Meter is designed for portable high accuracy illuminance and luminous color measurements in all SSL and traditional lighting application areas thanks to its compact design, high-quality light sensor and precise cosine field of view.

A powerful WiFi interface enables long distance wireless remote control of the light meter.

BiTec Light Sensor for More Accurate Light Measurement
One of the key features of the BTS256-E Wifi is its BiTec light sensor. The BTS combines a silicon photodiode with a noise-free CMOS diode array. Through bilateral correction of measurement signals from both sensors, the BiTec sensor ensures extremely accurate photometric and spectral radiometric measurement values over a wide dynamic range.

Fast and Linear Silicon Photodiode Detector Plus Diode Array Detector
BTS256E LED Luxmeter video The traditional light detector employing a silicon diode and a photometric correction filter still provides the best dynamic range, linearity and response time . But it cannot perform color measurements and cannot actively adjust to the target light source's spectral function. This is why the Gigahertz Optik Bi-tech sensor is also equipped with a CMOS diode array detector that works with the filtered photodiode detector. Its precise spectral match to CIE photometric V(λ) spectral curve is optimized by correction using the diode array's measured spectral data.

Optimized Signal to Noise Ratio
The noise component inherent in diode array light detectors has a significant effect on the signal to noise ratio (SNR) and hence on the quality of light measurement. A remote controlled shutter installed into the BiTec light sensor enables online compensation of the dark signals that are dependent on temperature and integration time.

Pulse Width Modulated (PWM) LED Lamps
The fast photodiode in the BiTec light sensor enables the BTS256-E to automatically synchronize itself to the test light frequency operated in PWM mode.

Cosine Corrected Field of View
A cosine corrected field of view is absolutely necessary for accurate illuminance measurements. For extended illuminance sources the exactness of the cosine match has significant influence on the light meter measurement uncertainty. The BTS256-E light meter is equipped with a 20mm diffuser window for a high level cosine match. Both BiTec light sensor detectors are centrally aligned behind the diffuser window ensuring the same viewing angle.

Quality Luxmeter
Through the cutting-edge Bi-Technology sensor concept, state-of-the-art electronics, online dark signal adjustment and the possibility to perform temperature compensation the BTS256-E represents the next generation photometer for all light measurement applications.

Broad Range of Photometric and Colorimetric Measurement Quantities
A much broader diversity of measurands as those offered by conventional light meters is required for verification and testing of LEDs and SSL. The BTS256-E Wifi measures fifteen different quantities for complete characterization of any light source:

  • 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
  • Color purity
  • CRI Ra and R1 to R15 Color Rendering Index

Data Displays for Standard Measurement Mode
Several displays where only the most necessary and common photometric measurements are shown are available. The cursor buttons are used to switch between the displays.

Flexible Expert User Displays
More experienced users can individually configure and save displays allowing any measurement quantity to be selected.

Info Display for Measurement Parameters
An information display is available that shows all relevant measurement and set-up parameters.

Easy Operation and Handling
Three control buttons with well-structured menu navigation make for easy and safe operation. In the standard measurement mode for example, no user selection is required - all common measurement quantities are displayed. In the expert mode the user has access to all measurement parameters.

Many Extra Useful Functions & Features

  • Time delay allows selectable time to move out of detector view before light measurement
  • Automatic display dimmer dims display during light measurement
  • Acoustic signal can be set to mark the end of a light measurement
  • Displays can be enlarged for easy reading across the room
  • Illuminance distribution map can be created using a PC and single measurement points stored in the meter. 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 up to 100ms
  • Second data logger measurement mode that enables time-clocked recording of all measurands including the spectral data
  • Date and real-time can be set
  • ¼-20 tripod stand socket on bottom panel
  • Diffuser window cap with leash
  • Lanyard
  • Splash proof

Use without PC
The BTS256-E WiFi is equipped with all the functions necessary for computer-independent use. The rechargeable batteries provide eight hours of operation. The USB adapter cable can be used to recharge the battery even without a PC.

Use with PC
A USB2 interface is provided for use with a PC enabling data exchange and battery recharging. WiFi interface is also included.

User Software
Supplied S-BTS256-E software offers all the functions necessary for measurement, display of readings and data transfer. The flexible desktop software concept enables the user to select which measurement value windows to display on the desktop. This can either be just a full screen display of lux measurement values or a matrix containing numerical and graphical display fields. Each desktop configuration can be saved for later use.

Software Development Kit
For self-programmers the S-SDK-BTS256-E Software Development Tool option is available. The SDK is compatible with Lab View from National Instruments, NET from Microsoft and C/C++. The SDKs simplify incorporation of the BTS256-E series meters into user based systems.

Who is the BTS256-E WiFi Light-Color-Spectral Meter Designed For?
For large area exterior and facility lighting installations like warehouses where all the features and functions of the BTS256-E are required plus the WiFi option for remote control makes meter reading more practical.

Adobe Reader

Download the BTS256-E LED-Luxmeter Technical Data Sheet pdf file
(23 mb).

To Order The BTS256-E LED-Luxmeter, Call Us Today At 1-978-462-1818.


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
WiFi 2.4GHz, external unscrewable antenna,
Transmission range > 100m within visual contact
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
BTS256E min and max measurable spectral irradiance
Practical Solutions To Real Application Problems

Here's The Problem:
You are a lighting manufacturer that needs light measurement instrumentation capable of light and color qualification of your new Solid State Lighting (SSL).

The instrument must be able to accurately analyze LED and traditional light sources for comparison purposes.

Some of your fixtures are large in size so an integrating sphere would be required to measure total luminous flux. But the integrating sphere solution is out of the question due to the high costs, space requirements and maintenance involved.

Anyway, since your sources are designed for area illumination, for quality control purposes, illuminance measurements are more applicable than total luminous flux measurements in lumens.

Correlated Color Temperature (CCT) is most important to you.

However, the meter should reliably provide absolute as well as other color parameters and spectral data.

Here Are The Requirements:
A simple to operate, accurate light and color meter that can measure any type of light source in the field or in the lab. It must be:

  • field portable
  • battery powered
  • easy to read display
  • allow full remote control by PC for storing data, producing reports & tech spec sheets
  • competitively priced since multiple units will be required by field service personnel or possible use by technical sales department.

Here's The Solution:
For complete color, spectral and absolute analysis of SSL and any other light source the BTS256-E LED Luxmeter is the right tool.

Standard Configuration Display
Standard Configuration Display

User Configured Display
User Configured Display

Ratio of Scotopic and Photopic Illuminance with EVE Factor (IES TM-24-13)
Ratio of Scotopic and Photopic Illuminance with EVE Factor (IES TM-24-13)

Spectral Illuminance and Irradiance

Photopic and Scotopic Illuminance

Color Coordinates

Coloring Rendering Index and Tristimulus Values

Information Display Showing Meter Parameter Settings – Included with Measurement Data File
Information Display Showing Meter Parameter Settings – Included with Measurement Data File

Socket for Tripod Mount
Socket for Tripod Mount

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

Interested in discussing your LED measurement application? Give us a call!

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