Connect PQ1 inputs to the AC line that feeds your system, and connect its relay contacts to your control computer's digital inputs. Your software will know every time there is a sag, dip, swell, or impulse on the mains. Ultra-low cost, high-value.
Power Standards Lab
980 Atlantic Ave.
Alameda, California 94501
US: 1.888.SEMI.F47 or 1.888.736.4347