A comparison is made between shaketables driven by piezoelectric crystals and those of conventional design. The general construction of crystal shaketables and the auxiliary equipment necessary for geophone studies are discussed. The theory of geophone motion shows that a measurement of phase shift between the geophone output and the crystal shaketable driving voltage can be used to determine the nature frequency and damping of the moving mass of the geophone. The crystal shaketable gives a simple method for routine testing of geophones both in the laboratory and the field.
