Signal extraction from magnetic flowmeters for density measurements

DC type electromagnetic flowmeters generate signals proportional to the rates of flow of fluids in dosed pipes. These signals are processed and filtered suitably for flow measurements. Studies indicate that the generated signals carry secondary information on the characteristics of fluids, For instance, in slurry applications, the secondary information depends on the density of the slurry, the particle size distribution of solids and the types of materials used. The dependence manifests itself by having a frequency component and an amplitude component. A low-cost spectrum analyser is found to be effective in extracting the frequency dependent components. The amplitude variations of the signals can also be extracted using analog or digital techniques. A peak detector based on comparators and A/D conversion principles found to be capable of extracting the amplitude dependent components of the signals. By the use computers, the results obtained form the spectrum analyser and the peak amplitude detector can be correlated to the densities and other characteristics of slurries