Different techniques for measuring crustal deformation are now being tested at Pi¿on Flat Geophysical Observatory in southern California. As part of this comparison, we have analyzed five months of data from four different tiltmeters: three bodies borehole instruments, two 4.5 m and one 26 m deep; and a long-base (535 m) instrument at the surface. For periods from 1 hour to ten days, the signals from the deep borehole and long-base instruments show comparable noise levels; the shallow instruments are much noisier. Tidal analyses give results for the different sensors which agree to within the errors, which are several percent.