METHOD AND APPARATUS FOR DEVICE-DEPENDENT CALIBRATION OF RELAYS FOR HIGH ACCURACY OPERATION AT ZERO-CROSSING OF INPUT POWER SIGNAL

摘要

A system and method are provided for ensuring increased accuracy of individual relays (e.g., within a control system comprising a sensor) to close substantially coincidentally with respect to a current zero-crossing of an incoming power supply waveform. To determine timing of contact operation, a microcontroller operates the contacts in response to one of a series of test pulses, and determines the amount of time required for contact operation. The difference between timing of contact operation and zero-crossing is determined and adjusted to offset errors incurred by microcontroller threshold variations and power supply voltage variations. The calibrated value is then provided to the sensor in order to extend sensor life.