Hitachi OE700 Series, Руководство по эксплуатации

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4 Description of the instrument
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12 Hitachi High-Tech Analytical Science
4.2 Components and operating controls
The instrument consists of three important assemblies:
Excitation Source
A digitally controlled excitation source generates a strong electric discharge between
sample and electrode in the argon-purged spark stand melting a small part of the sample
material out of the surface, evaporating it and exciting it to glow in a plasma. The argon
atmosphere avoids oxidation on the sample surface and causes practically all discharge
energy to be converted at the sample connected as a cathode. The characteristic light
(e.g. blue for ferrous metal) contains the spectral information about the elements and
their contents in the sample.
Optics
The light generated in the spark stand is directed to a diffraction grating and there
dissected into its spectral components. Light with longer wavelengths is deflected
("diffracted") stronger than light with shorter wavelengths. This produces an emission
spectrum of the sample which can be measured using light-sensitive detectors. The
OE700 series uses optical sensors featuring a high sensitivity and long lifetime. The
optical system operates in a medium that ensures transparency even below approx.
200 nm.
The OE700 series has an argon-purged tube as light path ("direct light path").
Readout system
Recording a complete spectrum requires a fast readout system to process large
amounts of data fast. Light intensities obtained from the emission spectrum are
converted to contents using the calibration curves stored in the instrument.
The contents are displayed on the screen and further processed (quality detection,
monitoring of limit values for process control, etc.). The OE700 series uses a special
processor which allows the simultaneous evaluation of up to 16 individual sensors. That
permits very precise analysis by means of DIA (Dynamic Integration Algorithm).