I have a 1949 edition of the GE Manual of Electric Instruments Construction and Operating Principles which describes a 4 quadrant power factor meter of the polarized vane type it works like a miniature synchronous motor with a polyphase rotating field like a motor energized with the phase voltages and the rotor magnetized by one selected phase current the angle of the rotor directly represents the angle between voltage and current The book describes but sadly doesn t give a picture of a 360 degree 4 quadrant scale said to be useful for tie lines where the source and load ends can interchange The GE manual says to use a wattmeter and varmeter for any critical measurements because a single current coil power factor meter produces meaningless results in an unbalanced system