Valve position monitor and control system

A valve position monitor and control circuit for an electrically operated valve unit including at least two movable elements representative of the open or closed position of at least two valves of the valve unit, said circuit comprising:

• detection means positionable with respect to each of the movable elements of the valve unit to provide output signals representative of the position of the valves;
• valve actuation circuit means for providing command control signals for application to the valve unit to operate the electrically actuated valves of the valve unit,
• comparator circuit means coupled to said detection means and to said valve actuation circuit means for comparing the command control signals with signals from said detection means to determine if the valves are in the position commanded and to provide electrical output signals representative of such determination;
• circuit means couples to said comparator circuit and to said valve actuation circuit means to deactivate said valve actuation circuit means when the actual position of a valve does not correspond to a commanded position, wherein said circuit means includes a delay circuit means coupled to said comparator for delaying the electrical signals therefrom for a predetermined time to permit a valve to respond to a valve control signal from said actuator circuit means;
• and
• wherein said comparator has two output terminals and said circuit means further includes first and second pairs of solid state switches one of the switches of each pair having a control input terminal coupled to one output terminal of said comparator and the other of the switches of each pair having a control input terminal coupled to the remaining output terminal of said comparator, said valve actuation circuit means includes two control relays, wherein one pair of said solid state switches is coupled to one of said control relays and the other pair of said solid state switches is coupled to the remaining control relay to selectively apply power to said relays in response to signals from said comparator.