definitions (glossary)

we have provided definitions to commonly used terms on edaphic.com.au in the list below. If you see any mistakes, obvious omissions, or want to leave any comments please contact us.

 

  • absorbance: the ability of a layer or substance to draw in (absorb) light.
  • candela: SI unit of luminous intensity.
  • CCD spectrometer: Rainbow Light Technology’s unique spectrometer technology which converts photons into electrons for further computational analysis.
  • CCT: correlated colour temperature.
  • chromaticitycolour quality (the quality of colour), independent of brightness (luminence).
  • CIE 1931: a method for defining colour, developed in the 1930’s by the International Commission on Illumination (usually abbreviated CIE for its French name, Commission internationale de l’éclairage). The CIE 1931 quantifies the links between actual physical wavelengths of the electromagnetic spectrum and colour as perceived by humans in the visible part of the electromagnetic spectrum.
  • CRI: colour rendering index or colour rendition index. A scale or quantitative measure of the ability of a light source to reveal the actual or real colours of objects when compared with an ideal light source. The maximum CRI value is 100 which represents no colour differences between the measured and ideal light source. Typical LEDs have values greater than 80.
  • dielectric permitivitythe ability of a substance to hold electrical charge. In soil science, the dielectric permitivity (ε) relates to how much water is present in a volume of soil or substrate. A value of 1 represents air and a value of 80 is pure water. Dry soil typically has a value around 5 and saturated soil has a value around 50 to 60.
  • diode: a semi-conductor device, typically allowing the flow of current in one direction only, with two terminals.
  • ECE Standard: Economic Commission for Europe set standards for LED lighting in vehicles, among other activities. ECE Standards applies to countries that have signed the 1958 agreement on uniform technical prescriptions for wheeled vehicles.
  • emittance: the energy radiated by the surface of a body per second per unit area.
  • emissivity: the effectiveness of a material, such as a surface, organic matter (plant tissue such as a leaf), or any other body, in releasing (emitting) energy as thermal radiation.
  • FWHM: full width at half maximum.
  • LED: light-emitting diode (when a voltage is applied to a semi-conductor diode, the diode glows and emits light).
  • LED bins: chromaticity bins.
  • lumen (lm): SI unit of luminous flux (or flow). One lumen is equal to the amount of light emitted per second in  unit solid angle of one steridian from a uniform source of one candela.
  • luminous: producing or seeming to produce light.
  • luminous flux: a measure of the perceived power of light. Lumen (lm) is the SI unit of luminous flux. The human eye is sensitive to various wavelengths of light and luminous flux is adjusted to reflect this.
  • MacAdam, David: a 20th century physicist who foundered a method to categorise different colours.
  • MacAdam Ellipse: all colours which are contained in an ellipse within the chromaticity diagram which are indistinguishable from colours outside of that ellipse.
  • Megafauna: Often referred to the large mammals that are now extinct that lived during the Pleistocene and Holocene
  • MEMS (microelectromechanical systems): the technology of very small devices. Optical MEMS are an evolution of traditional optical spectrometers which allows them to be cheaper, smaller, and easier to use.
  • PPF (photosynthetic photon flux): the rate of solar radiation in the wavebands between 400 and 700nm (PAR or VIS) contacting a surface usually expressed as υmol m-² s-¹.
  • reflectance: the proportion of incident light which falls on a surface and is reflected.
  • SAE Standards: Society of Automative Engineers Standards is an automotive and aerospace standards setting body. SAE sets standards for LED performance in cars and aeroplanes and is based in the USA.
  • solid state lighting (SSL)the family of light sources known as LED (light emitting diodes) as opposed to other light sources such as electrical filaments, plasma (fluorescent lamps) and gas.
  • TDR (time domain reflectometry): a soil moisture measurement technique based on measuring the dielectric permitivity of a soil through timing an electrical pulse along a known length of rod. In dry soils the electrical pulse travels relatively quicker than wet soils where moisture slows the rate of propagation.
  • transmittance: the proportion of light which passes through a body or surface without being absorbed.