The present invention provides a method for approximating zeros of polynomials using an iterative technique and displaying graphical images based on the results of that technique. A first pulley is coupled to and concentric with the shaft. A clamping arrangement is provided for applying a clamping load to the first and second housing parts so as to urge first and second valve surfaces respectively thereof into substantially sealing engagement. One end of the resilient member abuts the shaft and an opposite end of the resilient member abuts the latching member. The diaphragm is exposed to the pressure of the pressure control region. The conductive member is capacitively coupled to the thermal unit but free of direct electrical connection thereto.