A calibration procedure to obtain solid concentrations from digital images of bulk powders

In this work, different approaches to obtain calibration curves of powder concentration from digital images of bulk materials are reviewed and compared. It is shown here that a logarithmic relation between the grey scale values of the bed images and the powder volume fraction produces a high quality calibration curve without the need of fitting constants. This conclusion is valid both for our experimental data and other previously published that have used polynomial equations to define calibration curves.