CSLMS Medium Sphere Spectroradiometers

Measure the spectral flux of small to medium lamps and luminaires

Labsphere's CSLMS medium spectroradiometers are based upon 10 & 20-inch (0.25 & 0.5m) interior access integrating spheres and are purpose designed for measuring the luminous flux from small to medium luminaires and lamps. A CDS-series spectrometer controlled from LightMtrX software provides for ease-of-use, instant acquisitions and powerful analysis.

Measure Total & Forward Flux

The CSLMS 1000 can accomodate light sources of up to 100W and up to 3 x 3cm, whereas the CSLMS 2000 is suitable for sources of up to 400W measuring up to 5 x 5cm. Although not specifically designed to accept small tubular lamps or arrays of LEDs, the 10 and 20-inch spheres can be adapted on a custom basis to accomodate linear samples measuring up to 2/3 of the sphere diameter. Each sphere is also fitted with a 2-inch external source port which permits unobstructed mounting of board-mounted or heat-sinked devices for forward and partial flux measurements. A port plug (blanking plate) is supplied to seal the external source port when not in use. This port can be enlarged on a custom basis to accomodate larger samples, for example downlighters.

Accurate & Reproducible Readings

The Labsphere CSLMS-series integrating sphere spectroradiometers fully comply with CIE Publication No. 84, IESNA LM 78, IESNA LM 79 for 4π flux and the ANSI flashlight standard. All of which means that you can count on your CSLMS sphere spectroradiometer to yield accurate, reproducible results.

Not Just Any Sphere - This is a Labsphere Integrating Sphere

The LMS series integrating spheres benefit from Labsphere's 30 years of experience. The LMS-100 (10-inch) and LMS-200 (20-inch) integrating spheres feature convenient, clamshell-type interior access and stand on rugged, bench-top extruded aluminium frames. Both spheres are painted with Labsphere's Spectraflect integrating sphere coating which exhibits high, diffuse reflectance. Each sphere is equipped with a 1-inch port for the optional auxiliary lamp, the 2-inch port for use with externally mounted samples (which can be enlarged on request), and a further 1-inch port for mounting an optional temperature probe. Both spheres feature a 1-inch port adjacent to the south pole for electrical feed-through for the device under test; additionally, the LMS-200 provides for base-up as well as base-down mounting of the device under test so features an additional 1-inch port for electrical feed-through located close to the north pole. Removeable port plugs are supplied for all port openings.

The optical fibre feed to to the CDS-series spectrometer attaches to a ½-inch port on the LMS-100 that is equipped with a cosine diffuser, while the optical fibre connects to a 3-inch satellite sphere on the LMS-200 which provides for an optimal cosine response and reduced angular sensitivity.

The lamp mount is a telescopic design so a quick twist adjusts the position of the lamp. The height-adjustable sample platform features tapped holes and electrical feed-through which allows simple mounting of the device under test in the centre of the sphere for 4π flux measurements. Both spheres feature a lamp mount fitted at south pole position, while the LMS-200 also provides for suspending the lamp post from the north pole so that the test lamp can be held in either a base up or a base down orientation. Fixed baffles give optimal detector screening. The quick-connect internal and external electrical contacts allow for effortless substitution between different samples. Please note that the baffle which screens the detector port is designed to block light from samples mounted in the geometric centre of the sphere; care should therefore be taken when measuring samples that exceed the maximum size recommended and advice sought from Pro-Lite.

Not Just a Sphere Either

At the heart of each CSLMS system is the LMS integrating sphere. In addition, each system is equipped with a socket for the calibration lamp, a CDS-series CCD spectrometer with optical fibre coupling to the sphere, an SCL-series standard lamp of spectral flux and a stabilised power supply for the calibration lamp. The CSLMS LED systems are offered with a choice of CCD spectrometer. The CDS-600 & 610 are uncooled spectrometers with a spectral response from 200-850 and 350-1000nm, respectively, although please note that the calibration range of the spectral flux standard lamp used to calibrate the integrating sphere system limits the overall working range to 350-1000nm. Alternatively, the CDS-1100 & 2100 spectrometers are available which are based upon TE-cooled, back-thinned CCDs with enhanced sensitivities - please contact Pro-Lite for further information on these options. Spectrometer control is from LightMtrX software - which should be ordered separately. The system includes a calibration certificate for the standard lamp, a cable to connect the lamp power supply to the bulkhead connector on the sphere frame (which in turn routes the electrical supply to the sample platform in the centre of the sphere) and a further cable that interfaces to the sphere at one end and is supplied with bare wires at the other to allow the operator to route power to the device under test from their own power supply.

LightMtrX Software for System Control

Each CSLMS spectroradiometer system is designed to be controlled from LightMtrX software. Labsphere's LightMtrX is quite simply the easiest to use software yet released for performing spectroradiometric, photometric and colorimetric measurements of LEDs and other light sources. LightMtrX features user-defined "methods", an auxiliary correction capability and the ability to perform electrical and optical testing in conjunction with a Keithley 2400 series SourceMeter.

Auxiliary Correction for Accurate Measurements

Integrating sphere spectroradiometers are calibrated by substitution. The lamp standard of spectral or luminous flux is placed inside the sphere and the spectroradiometer responsivity determined. The measured responsivity takes account not just of the light emitted from the standard lamp, but also the light absorbed. When a sample is placed within the sphere, the degree of absorption may well be different, particularly so if the the device under test is an LED in a housing with lens, reflector, heat sink or drive electronics attached. The presence of all of this hardware causes the self absorption of the sample to be much higher than from the standard lamp, with the result that the flux from the sample is under recorded.

There is, however, a very simple solution to this error. This is called auxiliary correction and involves the use of a low power, uncalibrated "auxiliary" lamp mounted on the wall of the sphere. This lamp is used to guage the relative absorption of the standard lamp compared with the device under test and to yield a correction factor that can be applied to subsequent readings of the luminous flux for the particular type of sample under test. All of the CSLMS spectroradiometer systems are available with an optional auxiliary correction lamp and companion power supply that can be used to fully correct for self absorption errors.

Moreover, if the sphere is used for forward flux measurements with externally mounted samples, the auxiliary lamp can also solve the problem of readings being too high. With a sample placed at the external source port, light that would have escaped and been lost through this port during the sphere calibration can now reflect back from the device under test and cause an over-estimation of the sample flux. In this case, the auxiliary lamp is used to guage the relative reflectance of the sample compared to the open port and to yield the appropriate correction factor.

Also Measure Intensity & Illuminance

In addition to measuring luminous flux, you can add the capability of measuring luminous intensity and illuminance to your CSLMS spectroradiometer system. Optional sensor heads can be attached to the optical fibre feed to the spectrometer that provide for alternative types of photometric measurements. The E-1000 irradiance sensor is an integrating sphere-based head with a near-perfect cosine response that is used for measurements of the spectral irradiance of light sources. The I-1000 & I-2000 intensity sensor heads provide for measurements of the spectral radiant intensity of individual LEDs in accordance with CIE publication number 127, condition A & B.

Specifications & Ordering Information

1. The external source port is 2 inches as standard. This can be enlarged on a custom basis. IES LM 79-08 recommends
    that the maximum port size is 1/3 that of the sphere diameter.
2. The spectral range of the CDS-600 is 200-850nm and for the CDS-610 it is 350-1000nm. However, the working range
    of the integrating sphere spectroradiometer system is set by the spectral flux standard lamp which is calibrated from
    350-1050nm.