ARL 3460 Metals Analyzer
Page 3/17
Technical Description
2
1.
SPECIFICATIONS
1.1
Function principle
The ARL 3460 Metals Analyzer is a simultaneous Quantometer. This means the instrument
measures the intensity of several spectral lines simultaneously in the light emitted by the sample,
when the atoms that compose it are exited by an external energy source. The analysed light is
located approximately into the 150nm to 800nm wavelength range. The whole measuring system
is therefore based on the physical phenomenon that is summarised as follows:
When certain energy is applied to an atom, some of its electrons change their orbit. When these
electrons return to their initial orbit, a precise energy is restored in the form of a light at a
determined wavelength. This is an atomic phenomenon, and consequently it is practically
unaffected by the chemical or crystalline form of the atom. This means the instrument can
determine, for example the quantity of silicon in steel; but will not give information about the form
under this silicon is to be found. The following figure gives a rough representation of this
excitation.
+4
+4
+4
Initial energy E
1
Energy E
2
Return to energy E
1
Supplied
D
E
Emission of photon of
wavelength
l:
E
2
- E
1
= h •
n
= h • —
c
l
Excitation of an atom
A sample containing several different elements will therefore produce light composed of
wavelength specific to each of the elements. By separating these wavelengths by a dispersion
system, the spectrometer can determine which elements are present, the intensity of each of these
wavelengths being a function of the concentration of the considered element. By measuring this
luminous intensity (with a photomultiplier) and by processing this information with a computer, the
instrument can thus determine the concentration of the considered element.
An instrument that allows such analysis is therefore composed of the four following parts:
1)
A source of excitation that supplies energy to the samples.
2)
A dispersion device that discriminates the different wavelengths.
3)
Electronics that measure the luminous intensity of each of the wavelengths.
4)
A computer that processes the measurements and controls the instrument.
1
2
3
4
Excitation
Spectrometer
Electronics
Computer
