Spectrometer in Paschen-Runge mounting

Belec spectrometer in Paschen-Runge mounting

For example the Belec spectrometers are spark emission spectrometers for rapid analyses of metals. An electrical discharge is generated. The test material is "sparked". Between an electrode and the test sample, positioned in a sparking stand or a probe, will generated a discharge via the spark generator. Thereby the material of the test sample is converted into a gaseous state. The atoms of the elements in the material are shifted to a higher state of energy. On returning to the normal state they emit the light with the characteristic wavelengths of the elements. This light reaches the entrance of a spectrometer directly (vario lab) or via a fibre optic (port). There is a narrow entrance slit (20µm), through which the light falls on the surface of an optical grating. This grating is concave and aluminium plated with 60 (vario lab) or 30 (port) mm Ø diameter and with 3600 groves per millimetre. Due to the large number of lines of the grating, the light is diffracted so much, that it gets resolved into individual wavelengths. These lines are images of the light falling through the entrance slit. A nearly linear spectrum is produced.

The chosen spectral lines for the analysis of specific elements are directed onto a light sensitive receiver (photo tube) via a 50 micron exit slit. The light which falls onto the photomultipliertube is directly related to the concentration of that element within the sample. The pulses generated proportional to the output current of the photo tube are counted and a computer calculates and displays the results in % or ppm on the screen. All analyses can be stored continuously and or printed out.