the temperature difference between the expansion curve 40 and the contraction curve 42 can lead to overshoot situations which creates an advantageous massaging action this massaging action is superimposed on the above described first action of pressure equalization to give a combined action this effect is created by designing the thermal circuit to create a meta stable system in response to the heat source this equation is a familiar property found in the differential equations of heat transfer fluid mechanics and electricity there is a continuously transient time varying response that frequently manifests itself as a sinusoidal output the electrical analog of this type of transient response is found in an electrical oscillator and is based on the rc tank circuits to set the time delays that are used to create and control the oscillations this oscillating property is designed into the polymer sensor causing a constant inflation and deflation of the cells over a slow cycle specifically the thermal properties of the materials and the dimensions used in the polymer control the cycle period and the frequency and amplitude of the oscillations note the difference in the heating and cooling temperatures of the polymers moving between liquid and solid phases because the polymer heats and expands at a higher temperature than it cools and contracts the cells tend to loose slightly too much pressure and reduce to a below equilibrium pressure and core height then after a cooling delay the valve closes and the cell re inflates to a slightly above equilibrium pressure before it is sufficiently heated to repeat the cycle this slow over and under inflation cycle interacts with the degree of.