Dr David Westmoreland
Technical Sales Engineer
+44 (0)1372 378822

Light Meters

Full range of light meters, radiometers and photometers

Light Meters

International Light Technologies offer a full range of light meters from economical lux/foot candle light meters to calibrated, NIST-traceable radiometers and photometers with a comprehensive selection of light detectors for measuring a variety of visible, UV, and infrared light sources such as lamps, LEDs, and lasers.

ILT Light Meters, Radiometers and Photometers can be configured with almost any one of the large selection of application-specific light sensors (light detectors), except belt radiometers (ILT400 and 490) which are self-contained and have specific spectral response models available.

Contact: Dr David Westmoreland
Technical Sales Engineer
+44 (0)1372 378822


  • Easy-to-use high performance instruments
  • Perfect for use as photometers, intensity meters, curing meters, power meters and flash meters
  • Calibration service for all meters and detectors
  • We offer a comprehensive consultation service to determine light measurement needs
  • Models

    ILT5000 Research Radiometer

    The ILT5000 is the ILT1700 for the 21st Century.  Improvements on the industry standard ILT1700 include rapid optical measurements (1-100hz), a broader dynamic range (100fA to 1mA), Datalight III for PC and Mac, plus built-in wireless, data storage, and rechargeable batteries.

    The ILT5000 is backwards compatible with the ILT1700 sensor configurations, as well as all of ILT's sensor accessories including filters, optics, integrating spheres and ISO 17025/NIST traceable calibrations.

    ILT5000 optical measurement systems typically consist of the ILT5000 light meter, a sensor, filter, optic and calibration to allow direct reading in the appropriate empirical units including lux, foot-candles, candela, lumens, watts, W/cm2, cd/m2, foot-lamberts, nits, etc.


    Measurement systems:

    The ILT5000 meter requires a sensor to measure light. Sensors are available to measure from 185 nm out to 40 micron and are supported with a vast array of accessory including bandpass filter, cosine receptors, integrating sphere, and numerous types of calibration.

    ILT1000 Light Meter Monitor & Data Logger

    The most versatile UV, VIS and IR data logging optometer available on the market today.   System configurations are based on the industry standard ILT1700 Research Radiometer/Photometer detectors, filter/optics and calibrations.

    The ILT1000 was designed with OEM and custom configurations in mind and can easily accommodate most solid state detectors, bypass filters and a vast selection of input optics. Integrating one or more ILT1000's into your system is easy, please contact us for more details.

    The ILT1000 is capable of measuring 8 decades of light intensity (i.e. nW/cm2,w/cm2) and providing direct readout in W, W/cm², Lux, Fc, Lumens, cd/m², cd, W/sr, W/sr/cm² and more.

    On board data storage allows continuous monitoring at customer specified sampling rates using the “set it and forget it” data logging.

    Applications include Camera/Phone flash photometry, Beacon-exit sign-aerospace effective candela measurements, Audience scanning/laser light show exposure, Germicidal, Pharmaceutical/cosmetics, Semiconductor, Lithography, Process Monitoring, Curing, Plant Photobiology, Thin Film Deposition, Ribbon Clarity/Glass Production and Liquid Turbidity, and Transmission Measurements.

    ILT2400 Hand-Held Light Meter & Optometer

    The ILT2400 is the most advanced hand held light meter and optometer on the market today.  ILT’s Accuspan software automatically sets the averaging while rapidly measuring over 8 decades of light intensities.  The internal software allows customers to capture a peak as brief as 100μS and to store up to 16 readings per second. The colour display works in both landscape and portrait mode.

    The ILT2400 supports numerous light measurement applications including Audience Scanning Laser Safety, General Purpose Light Measurements, Research, Sterilisation/UVGI, Solar, Photoresist – lithography, Optical Radiation Hazard, Phototherapy, Photo-Degradation, PPF & PPFD Plant Studies, and more.

    Measurement systems:

    The ILT2400 meter requires a sensor to measure light. Sensors are available to measure from 185 nm out to 40 micron and are supported with a vast array of accessory including bandpass filter, cosine receptors, integrating sphere, and numerous types of calibration.

    ILT6000 Rack Mount Multi System Radiometer

    Each ILT6000 rack mount kit includes 2 units, expandable to 10 units per rack (A6000 add on kit sold separately)

    Stand-alone or mount in standard 19” rack

    Run multiple systems simultaneously allowing measurements From 2 to 100 of units

    10 decade dynamic range of optical analysis

    Built in wireless (ILT6000A wired version)

    DataLight III software for Windows (7, 8, 10) and Mac IOS

    Labview compatible

    NIST-Traceable/ISO17025 accredited calibration and certificate

    ILT1400 Belt Radiometer

    The ILT400 Belt Radiometer is equipped with a solid-state detector for excellent long term stability and reduced cost over traditional vacuum phototubes. The ILT400 all-in-one Belt Radiometer, comes in three versions: ILT400UVA measures UVA from 315 – 390 nm, and the ILT400BAV is designed for broadband covering 275 – 485 nm.

    The ILT400 works with many UV lamp options from UV LEDs, Iron doped, H and D type UV lamps, as well as standard UV bulbs, but is not recommended for flashing or pulsed UV lamps.

    ILT490 Belt Radiometer

    The ILT490 versions contain the same vacuum phototube and filtration as the original IL390/IL290 to allow easy upgrades for existing ILT customers, assuring the same UV spectrum is measured.

    The ILT490 all-in-one Belt Radiometer comes in two versions: the ILT490 broadband UV for 250-400 nm, and the ILT490C UVC for 205-345 nm.

    The ILT490 works with many UV lamp options from Iron doped, H and D type UV lamps, as well as standard UV sources, but is not recommended for flashing or pulsed UV lamps. The ILT490 series has an auto shut off feature that stops measurement once less than the minimum exposure level is measured for 5 consecutive seconds.

    For customers needing long term integration, ILT offers a special version of code that does not have auto shut off (ILT490ON, ILT490CON). The “ON” code disables the profiling mode, allows long term measurement and displays the peak irradiance as well as  total integrated exposure.

    ILT70 Series Light Meters

    Simple, NIST-traceable, hand-held light meters/radiometers designed for routine use that can be customised with application specific detectors, labelling, graphics, and colours for OEMs and resellers.

    Developed to offer OEMs and resellers a versatile instrument, ILT70 Series Light Meters / Radiometers are available in standard models to measure UVA (Model ILT72CE), UVB (Model ILT73CE - broadband or narrowband), bilirubin (Model ILT74CE - irradiance and band irradiance units), and germicidal (Model ILT77CE).

    Custom sensors can also be designed for measurements between the spectral ranges of 200 and 1100 nm with readout in units of W/cm2, W/cm2/nm, W, lux, cd/m2, as well as other empirical units.

    ILT70 Series Light Meters / Radiometers can be further customised with a variety of feature sets including a hold function, exposure reading, and automatic shut-off.  Featuring a 4½ digit LCD that provides a direct readout, this rugged light meter/radiometer has a low-battery indicator and protective rubber boot available in several colours

    ILT Light Detectors

    ILT detectors are designed to emit low levels of current in the pico-amp to milli-amp range which is then converted to calibrated optical units such as lux, W, W/cm2... when used with ILT light meters. Detector assemblies typically include a sensor, filter, optic and calibration.


    Example of a calibrated detector assembly for lux: "SED033/Y/W" includes the “SED033” 33mm² silicon photodiode detector, the “Y” photopic correction filter with the “W” Diffuser and calibration.

    (Note: “/U” indicates an uncalibrated sensor).


    The SED and SPM type optical detector housings are made of black anodized aluminium, with female filter threads (1¼-24), a tripod mount (¼-20), and two end mounts (#8-32). Only these housings allow for filter selection/swapping and underwater modification. All underwater modified detectors (SUD) require the W wide-eye diffuser in addition to any other filters and come special order in 10, 50 or 100 foot lengths.


    These four versions do not have removable, swappable filters and cannot be made waterproof:

    The SCD type optical detectors are in a 42 x 19 x 14 mm housing.

    The SSD type optical detectors are ultra-low profile (31 x 41 x 4.3 mm) detectors for UV measurements.

    The XSD type optical detectors are in a 15 x 42 mm dia. housing with M6X1 tapped hole for mounting.

    SPD type detectors are in a 121 x 19 mm dia. pen style housing.

    ILT Optical Filters

    Optical filters are often used to attenuate certain wavelengths of light and produce an overall desired detector response.

    Interference filters rely on harmonic interference between waves to provide very narrow passbands. Thin metal films are spaced half the desired wavelength apart by a dielectric spacer.  Interference filters are capable of bandwidths less than 10 nm.

    Absorptive filters typically consist of glass that has been doped with a concentration of dye that absorbs particular colours. Since spectral transmission varies logarithmically with thickness, the band pass can be reduced by thickening the filter.

    Multiple colour filters can be layered to match a desired function, such as the CIE photopic response, which defines the eye's sensitivity to colour. The combined spectral response is the product of the filter's transmission and the spectral responsivity of the detector doped with a concentration of dye that absorbs particular colours. Since spectral transmission varies logarithmically with thickness, the band pass can be reduced by thickening the filter.

    ILT's optical filters are the building blocks that allow a myriad of applications. Mounted in threaded (1 1/4-24 thread) black anodized rings, all filters may be repeatedly interchanged on any SED, SEL, and SHD detector. Unmounted filters and empty filter rings are also available.

    ILT can also create weighted measurement functions for applications such as the new UV Actinic Hazard standard, where UV exposure at a critical wavelength has a proportionally greater effect (as defined by ACGIH, NIOSH) than exposure at nearby wavelengths. ILT weights the sensitivity at each wavelength using thin film techniques or composite absorptive layering to accurately indicate exposure levels in a single measurement.

    ILT Input Optics

    Light measurement units are defined around very specific spatial responses. A carefully designed input optics system is essential if measurement accuracy is to be achieved.  Two laws of geometrical optics apply directly to radiometry and photometry: the inverse square law and the cosine law.

    The inverse square law defines the relationship between irradiance from a point source and the distance to the measurement surface. It states that the intensity per unit area varies in inverse proportion to the square of the distance between the source and surface.

    In other words, if you measure 16 W/cm² at 1 meter, you will measure 4 W/cm² at 2 meters, and can calculate the irradiance at any other distance. A well defined measurement plane and approximate point source are required for valid interpolations.

    In radiance measurements (W/cm²/sr), where a detector with a narrow viewing angle looks at a much larger, uniform area source, the area of the source that the detector sees increases as the detector moves farther away, counteracting the effects of the inverse square law and making the reading independent of distance.

    Radiance measurements are useful for characterising large area sources such as CRT's and backlit displays, or for diffuse, uniformly illuminated surfaces.  The cosine law refers to the relationship between the irradiance on a surface and the incident angle. The intensity falls off in proportion to the cosine of the reflected angle, since the effective surface area is reduced as the angle increases.

    Irradiance and Illuminance detectors, especially those with filters that restrict off-angle light, require cosine correction to properly quantify light coming from all angles. Inaccurate cosine response is one of the biggest sources of error in full immersion applications.

    There are many applications in light measurement that require specialized input optics. For example, intense laser beams must be diffused so that the narrow beam does not locally saturate the receiver. Many high intensity ultraviolet sources require temperature resistant remote optics that offer cosine spatial responses and side viewing.

    ILT350 Illuminance Spectrophotometer

    The hand-held ILT350 Illuminance Spectrophotometer was designed for portability, quality and ease of use. The housing design is ergonomic and light weight yet packed with features such as a built in full colour display. Extensive data capture and analysis software, rechargeable battery and internal data storage. The menu buttons are intuitive and easy to use.

    The built-in 12 mm diameter cosine receptor is protected by a magnetic rubber cap that remains attached to prevent loss or damage. The toggle buttons allows the user to easily scroll up and down to view not only lux & foot candles, but also spectrum, CRI, CCT, tri-stimulus values, and more.

    The ILT350 has three measurement speeds including Fast (0.5 s), Slow (2.5 s) and Auto (0.5 – 27 s) depending on light intensities (20 lux to 100K lux). The spectral resolution is approximately 10 nm with an accuracy of ±3 nm. Relative spectral distribution data is exported in 1 nm increments using the light meter software.

    The internal memory can store up to 100 files and export data into Excel/Work formats.


    Applications include:

    Automotive Lighting

    Commercial and residential lighting designs and upgrades

    Display booth, colour and spectrum

    Comparison of traditional sources to LEDs

    Light efficiency testing

    Supplier info:

    For even more information, why not visit our suppliers website.





    © Quantum Design UK and Ireland Ltd 2018 - Website designed by Treefrog Design