2. Performance Indicators Definitions
1) Optical system: usually refers to the formal structure of the optical system, at present, domestic and international
institutions often used as a photometer industry type and CT auto collimation two structures;
2) Wavelength range: means for wavelength photometer can difference between maximum and minimum values of
the test;
3) Wavelength accuracy means the actual wavelength difference between the real wavelength and the setting
wavelength. Each wavelength photometer to be in a lot of points to check wavelength accuracy; spectrophotometer
wavelength accuracy is an important technical indicators, it qualitative, quantitative and structural analysis of the
impact is enormous. Way to check wavelength accuracy of many spectral lines as a standard filter praseodymium,
neodymium, holmium oxide filter, holmium oxide wavelength standard solution, deuterium lamp or low pressure
mercury lamp emission and interference filters and so on.
4) Wavelength repeatability: Wavelength Repeatability is the ability of the instrument to return the original
wavelength. It reflects the wavelength drive mechanism and the stability of the whole instrument;
5) Spectral bandwidth (sensitivity, resolution): refers to a peak spectral bands when the slit on the detector
detected through a monochromator energy half-width, expressed in nm wavelength, from another perspective to
understand this concept will more user-friendly: first, the monochromator exit slit represents not just the physical
size or geometry, it also represents the optical sense, this is the spectral bandwidth, we know that the light from the
failure of a single monochromator wavelength, but at a narrow wavelength spectral band are arranged in the order,
the number of spectral wavelength band comprises, represented by the spectral bandwidth. Spectral bandwidth is a
direct response to the quality level of monochromatic light from the monochromator out. The index with the
instrument resolution and sensitivity are similar, but different, they react photometer performance quality from
different sides. Resolution refers to the size of the instrument to distinguish two adjacent wavelengths ability
Sensitivity is measured at low concentrations do, when the concentration changes by one unit to the detector signal
caused by the change amount, it is subject to a calibration curve (standard curve as the horizontal axis, the
absorbance on the vertical axis) and a precision instrument itself restrictions. Two measurement precision of the
method is the same, the greater the sensitivity calibration curve slope, while the slope equal, the higher the
sensitivity, the better precision. It is noted that, in order to obtain accurate test results, the natural bandwidth of the
spectral bandwidth of the instrument (Spectral Bandwidth referred SBW) and the analysis of samples (Natural
Bandwidth referred NBW) ratio should be less than 0.1, more than 99.5% can be obtained so that the measurement
accuracy.
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