Page 9 - Shimadzu PDA-8000

Frequency Distribution Processing

Unlike conventional emission spectrometry that integrates the spectral intensity, Shimadzu's unique PDA method performs
frequency distribution processing on the spectral intensity of each discharge pulse.
For example, when a discharge spot is applied to inclusions such as manganese sulfide (MnS) or aluminum oxide (Al2O3), the
spectral intensity of that element is increased. When the spectral intensity of elements that readily form inclusions is converted
into a frequency distribution, the distribution form is not symmetrical. For these elements that readily form inclusions, accurate
results can be obtained by eliminating the data in the high intensity range from the statistical processing as inclusion data,
using the distribution analysis method. For elements that do not form inclusions, the shape of the frequency distribution is
symmetrical. Accuracy can be improved by selecting a processing method suitable for each element, such as the integration
method that integrates all the spectral intensity, or the partial integration method that divides the spectral intensity.

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Spectral intensity
Measured pulse intensities
transformed into frequencies

Time-series pulse data Time
Frequency distribution is normal Frequency distribution is Frequency distribution is widely dispersed
asymmetrical due to the
formation of an inclusion Frequency

Frequency
Frequency

Spectral intensity Spectral intensity Spectral intensity
Full integration method Distribution analysis method Partial integration method
• Intensity values are the sum of all • Intensity values are the intensities in the • Intensity values are the sum of intensities in the
intensities. specified locations. specified range.

Metallographic Analysis
There are 2 forms of aluminum in steel: aluminum oxide (Al2O3: insoluble Al) existing as particles with diameters about 5
m, and metallic aluminum (soluble Al).
The spectral intensity increases if aluminum oxide exists within the discharge spot.
After converting to a frequency distribution, information on aluminum oxides can be obtained from the part of the
distribution with high spectral intensity.
Speciation Analysis of Aluminum in Steel Discharge including insol Al
insol AI
sol AI insol AI

Frequency

Analysis sample surface (discharge crater) Discharge for sol Al only Spectral intensity

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