Abstract: A stationary plate assembly for a rheometer that selectively provides steady state and dynamic testing of melt viscoelastic characteristics of a material sample. The stationary plate assembly has a stationary sample plate magnetically coupled to its supporting member. Therefore, after the steady state testing is complete, the movable plate, material sample and stationary plate may be moved vertically away from the stationary plate supporting member. Therefore, any spurious, erratic rotations of the movable plate when the rheometer is switched form the steady state test mode to the dynamic test mode will not cause a further working of the material sample.