A highly desirable tool for mammalian cell culture based protein and virus production processes is a reliable on-line monitoring technique for cell concentration. Currently, various techniques are used including turbidity measurements, oxygen uptake rate (OUR), and dielectric spectroscopy. However, difficulties in differentiating viable from dead cells make turbidity difficult to use for accurate measurement, and OUR analysis can be difficult for mammalian culture due to much lower uptake rates than fermentation, especially at low cell densities and smaller scales. Dielectric spectroscopy, also known as capacitance, is a technology that has been studied extensively due to its ability to accurately track viable cell density based on the integrity of the nonconducting lipid bilayer membrane and allows measurements without significant process disturbance. However, capacitance is still a developing technology and shifts in cellular structure, changes in cell size, and mixing conditions can all affect reproducibility. In our work we seek to evaluate capacitance equipment from two vendors, as well as identify how variations could be minimized or corrected, in various cell lines. In addition, we discuss using on-line monitoring to control a bioreactor through SCADA-based automated passaging to provide a cell source for laboratory experiments. With this system we were able to fully automate a single bioreactor for multiple cell passages (>10) and generate a good correlation with off-line measurements of cell count.