What are soft bearing dynamic balancing machines and hard bearing dynamic balancing machines?

Few decades back, when balancing machines were introduced, the cradle on which the rollers were supported needed to be moved to measure the vibration levels due to unbalance. With the advent of technology and introduction of quartz transducers to measure force, it is no longer required for the cradles to oscillate to measure vibration. The machines which continued to have oscillating cradles and electro dynamic pickups to measure vibration were classified as soft bearing machines.
The machines which had rigid cradles devoid of any movement and measure force using piezo or other pickups are classified as hard bearing dynamic balancing machines. The basic design philosophy of hard bearing dynamic balancing machines is measuring force and the advancement of computational mathematics using microprocessors has enabled introduction of balancing machines whose calibrations are valid for the complete range of speeds, weights and quality requirements.
The algorithm used facilitates permanent calibration and host of other features for day to day use and extreme reliability.