2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/106899Diagnostic diagrams of electron density - excitation for a sample of 613 planetary nebulae are presented. The present extensive sample allows the definition of new statistical limits for the distribution of planetary nebulae in the log [Ha/[SII]] vs log [Ha/[NII]], log [Ha/[SII]] vs [SII] 6717/6731 and log [Ha/[NII]] vs [SII] 6717/6731 planes. The diagrams provide a good representation of the ranges of physical conditions, indicated by these emission line ratios, present in planetary nebulae during different evolutionary stages.6 pages, 7 figures. Accepted for RMAAAstrophysicstext