TOCS Thermal-Optical-Electrical Characterisation System

TOCS Sphere System

The Labsphere TOCS series of integrating sphere spectroradiometers provides complete thermal, optical and electrical characterisation of LEDs and LED modules in strict accordance with the IESNA standard methods LM-79 & LM-80. A TOCS system is based upon a 20, 40, 65 or 76-inch interior access sphere with provision for both 2pi forward & 4pi total flux measurements.

The amount and colour of light from LEDs varies greatly with both operating current and temperature. A TOCS integrating sphere system is a fully integrated, out-of-the-box spectroradiometer that can characterise the variation of luminous flux (in lumens) and colour (correlated colour temperature in Kelvin) from LED products as a function of temperature and electrical drive level. A TOCS spectroradiometer system saves time and money compared with performing thermal, electrical & optical characterisation tests manually, while the fact that the TOCS is a turn-key test station means no time is wasted integrating a system from disparate components.

Labsphere TOCS Spectroradiometer System

A TOCS system comprises an interior access integrating sphere coupled to a fast CCD spectrometer. The device under test is held on a temperature controlled electrical socket which is placed at the external source port on the sphere for 2pi flux measurements. The system includes a choice of calibration source (external 2pi, internal 2pi or 4pi), auxiliary lamp for correction of sample absorption and power supplies for the calibration and auxiliary lamps.

Users of existing Labsphere and Sphere Optics spectral lamp measurement systems may be able to upgrade their integrating spheres to a TOCS configuration. Please contact Pro-Lite to discuss an upgrade package.

Labsphere TOCS Spectroradiometer System

A TOCS spectroradiometer system is controlled from a Windows® PC using Labsphere;s menu driven TOCS applicstion software. The optical parameters reported include the spectral radiant flux, luminous flux, CIE chromaticity (xy, u'v'), correlated colour temperature (CCT), dominant wavelength, spectral purity and the colour rendering index (Ra, R1-14). The electrical parameters reported are the drive current and voltage, the power consumed, and the luminous efficacy (electrical to optical efficiency), reported in lumens per Watt. The case temperature of the LED or LED module is also recorded. TOCS software runs on both 32 and 64-bit versiopns of Windows XP, Vista or 7 operating systems.

The TOCS system software also provides an interface to a Keithley 2400-series SourceMeter®. The Source Meter drives the device under test under the automatic control of the TOCS software and in turn reports the electrical drive characteristics of the sample. A Keithley Source Meter is not included as standard with a TOCS system, but can be included upon request. This allows for those users with an existing 2400 series SourceMeter who wish to use it with a TOCS system.

TOCS software allows users to control the LED temperature and operating current at specified ranges. This control enables the software to measure and characterise the device under test over a wide range of temperatures. System software can automate procedures for measuring the spectral characteristics and controlling current and temperature. Software simultaneously collects electrical, optical and thermal data which is graphed and viewed on screen, or can be exported to a spreadsheet for further analysis.

At a nominal ambient temperature of 25°C, the temperature of the device under test can be held continously from 10 to 85°C (depending upon the electrical power dissipation of the sample). TOCS software provides for automated measurement of the following parameters:

► ILV @ constant T: step & control I, stabilise T, measure L & V
► VLI @ constant T: step & control V, stabilise T, measure L & I
► TLV @ constant I: step & control T, stabilise T, measure L & V
► TLI @ constant V: step & control T, stabilise T, measure L & I
► ILV/T: perform ILV @ constant T, step T and repeat at each T
► VLI/T: perform VLI @ constant T, step T and repeat at each T

(where L = luminous flux, V = Voltage, I = current and T = temperature)

The TOCS sample holder mounts to the 2pi forward flux measurement port on the integrating sphere. The inside face of the sample holder is painted with Spectraflect diffuse reflectance coating to enhance sphere collection uniformity and provides the electrical connection to the Keithley SourceMeter and the temperature controlled LED socket. The thermoelectric controller allows the case temperature of the LED to be varied continuously from 10 to 85°C (the actual range will depend upon the power dissipation of the device under test).

To meet your exact needs, we can equip the TOCS integrating sphere with ambient air temperature control. We can also supply bespoke, device-specific mounting apertures for the forward 2pi flux measurement port on the sphere.

For full specifications for the TOCS spectroradiometer systems, click here to download the datasheet.