Abstract Voltage sensing apparatus for detecting a change in an AC voltage across a line and actuating an alarm when the change occurs. In a preferred embodiment of the invention, the alternating current voltage across the line is converted into a train of square wave pulses, each of which has a pulse width which is a function of the amplitude of the alternating current voltage. A pulse width detector means receives the train of pulses and triggers an alarm means when the pulse width of any one of the pulses in the train varies with respect to a predetermined pulse width. The apparatus is particularly useful in a three-phase system to determine if the voltage across any one of three lines in the three-phase system drops below a reference voltage level.
Apparatus for determining if an alternating voltage from an electrical source applied across a line is less than a reference voltage level, said apparatus comprising: a. an actuable alarm, and b. alarm actuating means coupled to said alternating voltage source and said alarm including: i. means for producing a square wave pulse the width of which varies inversely as the function of the amplitude of said alternating voltage, and ii. pulse width detector means responsive to the pulse width of said square wave being greater than a predetermined width for actuating said alarm.
Claim 2
Dependent Claim
93 words
Apparatus for determining if an alternating voltage from an electrical source applied across a line is less than a reference voltage level, said apparatus comprising: a. an actuable alarm, and b. alarm actuating means coupled to said alternating voltage source and said alarm including: i. means for producing a square wave pulse the width of which varies inversely as the function of the amplitude of said alternating voltage, and ii. pulse width detector means responsive to the pulse width of said square wave being greater than a predetermined width for actuating said alarm.
Claim 3
Dependent Claim
32 words
The invention as set forth in claim 1 further including optical coupler means disposed between said square wave producing means and said pulse width detector means for providing complete electrical isolation therebetween.