What is plane separation, cross effect, influence?

In two plane dynamic balancing machines, the results are indicated in two correction planes. When a correction is made on one plane, the effect of the unbalance compensation on the second plane, is defined as plane separation or cross effect or influence.
Normally, the plane separation will be well below 3 %. In computer based hard bearing dynamic balancing machines, the plane separation is achieved mathematically. So users tend to get better levels of plane separation on computerized hard bearing dynamic balancing machines and that is not the case with soft bearing machines wherein unbalance signals are electronically mixed and modulated for indicating the results.