A fluorescent lamp sensor system is provided. The fluorescent lamp sensor system includes a plurality of bulbs and a plurality of electrodes coupled to the bulbs. A balanced differential circuit measures changes in electric fields produced by the bulbs in front of the electrodes. The balanced differential circuit includes a symmetric current source associated with alternating the surface potential of the bulbs. A current mode detection circuit detects the current associated with the capacitive effects of the balanced differential circuit. A synchronous detection circuit isolates the capacitive effects of the symmetrical current source from stray signals that differ in either frequency or phase.