The exciter has been designed to overcome the restrictions usually encountered with conventional exciters as regards poor signal-to-noise ratio, cross-axis components and non-linear distortion. A tilting tables rests on a special foundation.
An air-borne straight mechanism with a guide length of 1,2 m has been mounted on the tilting table. The electrodynamic drive system has been fixed on top of it. The tube-like magnetic system houses the driving coil. It has been linked by a fastener to the air-borne element of the straight mechanism on the lower side and to the test object mounting table on the upper side.
A magnetic field of constant density has been built up in the air gap over a length of more than 1 m by generation of a magnetic circuit, using two permanent magnets arranged opposite to each other at both ends of the system and a soft magnetic core of variable diameter. The characteristic features of the low-frequency exciter are the frequency range from 0,01 Hz to 20 Hz, the displacement amplitude range from 0,5 µm to 0,5 m, a maximum transverse motion of 0,1 % of the measurand at displacement amplitudes >5 mm, and an acceleration distortion of less than 1 %.
Low-frequency acceleration exciter