Radiometers

Radiometry is the measurement of radiation in the electromagnetic spectrum. This includes ultraviolet (UV), visible and infrared (IR) light.

Electromagnetic radiation is characterised by its frequency of oscillation. The frequency determines the "colour" of the radiation. The speed of light is a constant, and frequency is related to wavelength by the relationship c=fλ: Where c = velocity of light; f = frequency of oscillation; & λ = wavelength of light.

The preferred units of measurement for wavelength are nm or µm, (nanometers or micrometers/"microns").

The visible region of the electromagnetic spectrum can be divided into the basic colours of the rainbow: red, orange, yellow, green, blue, indigo and violet. Red light has the longest wavelength in the visible region (770 nm). Violet has the shortest (380nm).

Ultraviolet light is shorter in wavelength than visible light. It extends from 10nm to 380nm. And like the colours of the visible region, UV can be subdivided into smaller regions. The UVA region ranges from 380nm down to 340nm and is the least harmful of UV radiation. The vacuum-ultraviolet (VUV) and UVC regions are shorter and are important to the study of cancer. Infrared light extends from 770 nm to 100 microns. Its regions are known as near-IR, mid-IR and far-IR.

Measurements of optical radiation require specific methods to obtain accurate measurements. UDT supplies calibrated detector/filter combinations that cover from 200-1800 nm (0.2 to 1.8 mm). To obtain accurate measurements, one must understand the light source (i.e. laser, lamp, LED); the optical medium (i.e. air, water, optics); and the particular response characteristics of the detector.

Radiometric Sensor Heads & Minispheres
This range of sensor heads and minispheres is designed for use for a wide range of different applications. Different sensor materials are used; Silicon, Germanium and InGaAs. These three materials jointly provide coverage of wavelengths from 200nm through to 1800nm. In addition to this, detectors are available in different sizes, and with filters pre-fitted to flatten response.

Sensor head or Minisphere?
Sensor heads provide the highest sensitivity. They are prone to saturation if used with a source of high power density. It then becomes necessary to use a minisphere, which provides higher power handling capability as it reduces the effective power density seen by the detector.