Method and apparatus for device-dependent calibration of relays for high accuracy operation at zero-crossing of input power signal

Abstract From the Canadian patent

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 , …