Abstract: An improved microwave pulsed and computer-operated resonance chamber system for obtaining various parameters for a multimode chamber with or without a specimen therein. The system is generally made up of a continuous microwave signal source arrangement for transmitting a series of pulses to the interior of the chamber at one point thereof. A detector for sensing a transient relaxation response curve after each pulse in the chamber where the sensing is effected at a second point in the chamber and where the curve is representative of the relative field strength in the chamber. In one embodiment of the system the carrier frequency of the series of pulses is selectively adjusted so as to alter the multimode characteristics of the chamber in order to provide different transient relaxation response curves by the chamber. In a second and third embodiment of the system, selective rotatable tuning means is provided at a third relatively spaced point in the chamber for altering the mode characteristics thereof.