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(Abridged) Planetary nebulae (PNe) around Wolf-Rayet [WR] central stars([WR]PNe) constitute a particular photoionized nebula class that representsabout 10% of the PNe with classified central stars. We analyse deephigh-resolution spectrophotometric data of 12 [WR]PNe. This sample representsthe most extensive analysed so far, at such high spectral resolution. We aim toselect the optimal physical conditions in the PNe to be used in ionic abundancecalculations that will be presented in a forthcoming paper. We acquired spectraat LCO with the 6.5-m telescope and the MIKE spectrograph, covering awavelength range from 3350 to 9400 A. The spectra were exposed deep enough todetect, with signal-to-noise ratio higher than three, the weak ORLs of OII,CII, and other species. We detect and identify about 2980 emission lines,which, to date, is the most complete set of spectrophotometric data publishedfor this type of objects. From our deep data, numerous diagnostic line ratiosfor Te and Ne are determined from CELs, ORLs, and continuum measurements.Densities are closely described by the average of all determined values forobjects with ne<10^4 cm-3, and by ne([Cl III]) for the densest objects. For Te,we adopt a three-zone ionization scheme, where the low ionization zone ischaracterized by Te([NII]), the medium ionization zone by Te([OIII]) and thehighest ionization one by Te([ArIV]) when available. We compute Te from the HIPaschen discontinuity and from HeI lines. We do not find evidences of thepresence of low-temperature, high-density clumps in our [WR]PNe from theanalysis of faint O II and N II plasma diagnostics. The behaviour ofTe([OIII])/Te([NII]) being very low for high ionization degrees can bereproduced by a set of combined matter-bounded and radiation-bounded models,however, for the lowest temperature ratios, too high metallicity seem required.

Analysis of chemical abundances in planetary nebulae with [WC] central stars. I. Line intensities and physical conditions