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Sampling of Autocorrelating Powder Flows
Author(s) -
Heiskanen Kari,
Niemelä Oili
Publication year - 1993
Publication title -
particle and particle systems characterization
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.877
H-Index - 56
eISSN - 1521-4117
pISSN - 0934-0866
DOI - 10.1002/ppsc.19930100207
Subject(s) - autocorrelation , sampling (signal processing) , grinding , coherent sampling , statistics , materials science , mathematics , physics , metallurgy , optics , detector
Sampling powder flows in industrial grinding circuits are discussed. Work was done with different types of sampler and with different minerals and sampling objectives. It was found that all the samplers showed marked autocorrelation in sample mass for all the minerals ground. Typical autocorrelation could be found at both high (1 · 10 −3 –15 · 10 −3 Hz) and low (1 · 10 −4 – 4 · 10 −4 Hz) frequencies. Higher frequencies were attributed to powder transport and low frequencies to mill circuit variations. The effects of the found autocorrelation on systematic errors and on industrial sampling schemes are discussed. Systematic sampling produced large errors if operated at sampling intervals that were high‐frequency autocorrelation frequencies or small multiples of these. Low‐frequency autocorrelation was less detrimental to the sampling results.