Irradiance and Radiometry

Radiometry measures optical radiation, including the visible portion of radiant energy. Irradiance is a parameter of radiometry. It describes the amount of radiant power impinging on a surface per unit area. These measurements can be conducted in the UV, VIS, and NIR wavelength ranges.
Avantes works with various irradiance applications, ranging from pulsed solar simulator characterization to free space measurements of radiant sources such as street lights.

Configuring a Setup

The AvaSpec line of instruments provides exceptional resolution and stray-light rejection to ensure the accuracy of these measurements. Typical system configurations involve one or more spectrometers configured for the appropriate range of 200-400 nm for UV irradiance, 360-1100 nm for VIS irradiance, and 1100-2500 nm for NIR irradiance. While broadband configurations covering 200-1100 nm are feasible with one spectrometer, optimal performance is achieved through dedicated UV (200-400 nm) and VIS/NIR (400-1100 nm) channels in a dual-channel setup. The most commonly used spectrometer for these measurements is the AvaSpec-ULS2048CL-EVO because of its versatility and high resolution.

The spectrometer or group of spectrometers is connected via fiber-optic cable to a diffuser with a known surface area. The entire system is calibrated against a NIST-traceable source. Avantes offers a variety of cosine diffusers and integrating spheres for irradiance applications. The calibrated system is shipped as an integrated system (connected together) and should remain in this configuration to ensure the calibration’s integrity. FC/PC connectors are recommended in lieu of the standard SMA, which enables repeatable disconnection and re-insertion of the fiber optics so that the system can be disconnected for transportation.

Customers who wish to conduct their calibrations may consider one of Avantes’ intensity calibration sources. The AvaLight-HAL-CAL-Mini is available for VIS/NIR wavelengths (360-2500 nm), and the AvaLight-DH-CAL is available for UV/VIS wavelengths (200-1100 nm).

The Avantes AvaSoft-IRRAD software module enables irradiance parameter measurements such as radiometric quantities – µWatt/cm2, µJoule/cm2, µWatt or µJoule, photometric quantities Lux or Lumen, color coordinates X, Y, Z, x, y, z, u, v, color rendering index and color temperature, and a number of photons µMol/s•m2, µMol/m2, µMol/s, and µMol. AvaSoft-IRRAD software also facilitates the performance of irradiance intensity calibrations.


Avantes has developed a bundle, especially for irradiance measurements. This bundle includes everything you need to get started with your irradiance measurements. 

These are some of the products mentioned above. Contact one of our sales engineers for advice to find the perfect setup for your specific application.

Application Examples

Below are detailed application notes on various uses of irradiance spectroscopy in different applications and industries.

Why choose Avantes for your irradiance application?

  • High resolution and stray light rejection to ensure accuracy
  • Assortment of calibrated accessories and light sources
  • Software package especially designed for optimum irradiance measurements
  • Extensive knowledge and experience with various irradiance applications

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