and barium sulphate coated integrating spheres are often used to ensure accurate UV measurement. Monochromator To perform spectral analysis of a source, monochromatic light at every wavelength would be needed to create a spectrum response of the illuminant. A monochromator is used to sample wavelengths from the source and essentially produce a monochromatic signal. It is essentially a variable filter, selectively separating and transmitting a specific wavelength or band of wavelengths from the full spectrum of measured light and excluding any light that falls outside that region. A typical monochromator achieves this through the use of entrance and exit slits, collimating and focus optics, and a wavelength-dispersing element such as a diffraction grating or prism. Modern monochromators are manufactured with diffraction gratings, and diffraction gratings are used almost exclusively in spectroradiometric applications. Diffraction gratings are preferable due to their versatility, low attenuation, extensive wavelength range, lower cost, and more constant dispersion. Single or double monochromators can be used depending on application, with double monochromators generally providing more precision due to the additional dispersion and baffling between gratings. Detectors The detector used in a spectroradiometer is determined by the wavelength over which the light is being measured, as well as the required dynamic range and sensitivity of the measurements. Basic spectroradiometer detector technologies generally fall into one of three groups: photoemissive detectors (e.g. photomultiplier tubes), semiconductor devices (e.g. silicon), or thermal detectors (e.g. thermopile). The spectral response of a given detector is determined by its core materials. For example, photocathodes found in photomultiplier tubes can be manufactured from certain elements to be solar-blind – sensitive to UV and non-responsive to light in the visible or IR. CCD (Charge Coupled Device) arrays typically one dimensional (linear) or two dimensional (area) arrays of thousands or millions of individual detector elements (also known as pixels) and CMOS sensors. They include a silicon or InGaAs based multichannel array detector capable of measuring UV, visible and near-infra light. CMOS (Complementary Metal Oxide Semiconductor) sensors differs from a CCD in that they add an amplifier to each photodiode. This is called an active pixel sensor because the amplifier is part of the pixel. Transistor switches connect each photodiode to the intrapixel amplifier at the time of readout. Control and logging system The logging system is often simply a personal computer. In initial signal processing, the signal often needs to be amplified and converted for use with the