I am using a high temperature probe in 85070 Dielectric Probe Kit for measurements of planar solid samples. The flatness of the sample fulfill the requirements given in the manuel (i.e. better than 25 micrometers), as well as the sample diameter (>20mm). However, the probe itself is not flat: the steel part between the coaxial probe center and the outer rim (given in description as "Inconel") is not flat, but would trap some air between the probe and the sample. Has anybody characterise the error that this causes? I understand that the probe is recommended for liquids but the Quick Reference clearly states the "flatness" of the sample, which indicates to me that its use for solids is ok as well.