The non-radioactive Sondex Fluid Density Inertial (FDI) tool uses the inertial response characteristics of a vibrating tuning fork to determine the density of the wellbore fluid mixture. The Sondex Fluid Density Radioactive (FDR) tool uses low energy gamma rays to determine the downhole fluid density during a production log. It provides a reliable measurement that is unaffected by well deviation and flow rates. The Sondex Gas Holdup (GHT) tool provides a reliable full-bore measurement of gas volume fraction, independent of flow regime or well deviation.