Apparatus and method for establishing a reference signal with an lvdt

Abstract

A system for creating a position reference signal includes a linear variable differential transformer (LVDT), a magnetically permeable core capable of entering and existing the chamber of the LVDT, a positioning means for moving the core in forward and backward directions through a home location in which the core is within said LVDT, and a signal conditioner means for receiving the signals from the secondary windings and outputting a value so that when the core approaches the home location from the forward direction, the value first changes polarity only when the core passes through the home location. Preferably, the value is always positive or always negative when the core is at a location outside of the chamber. A process of creating a reference signal includes moving a magnetically permeable core from outside of a chamber of an LVDT to inside the chamber, creating an output signal from the voltages of the secondary windings of the LVDT, and sending a signal to a control means when the output signal changes from positive to negative after the voltage of one of the secondary windings has peaked for all possible locations of the core.