Abstract: A sensor system for detecting a vehicle on a driving surface includes a sealed casing, an integrated circuit vehicle detector, an integrated circuit transmitter and controller, and a battery. The sealed casing has a top surface and defines a cavity therein. The integrated circuit vehicle detector is disposed within the cavity and is configured to generate a vehicle present electrical signal when the vehicle is within a predetermined distance from the sensor system. The integrated circuit transmitter and controller is disposed within the cavity and is in communication with the integrated circuit vehicle detector. The integrated circuit transmitter and controller is configured to generate a vehicle present radio frequency signal in response to the vehicle present electrical signal. The battery is disposed within the cavity and is electrically coupled to the integrated circuit vehicle detector and the integrated circuit transmitter and controller.

Abstract: A capacitance measurement circuit and probe includes a drive circuit couplable to a constant-current source, a threshold detector, a probe capacitor, and a reference capacitor. The circuit includes a plurality of switches being actuatable to alternately couple the current source to the probe capacitor and to the reference capacitor. The drive circuit is configured to alternately generate a signal of linear ramp waveform having a slope that is proportional to the magnitude of capacitance of the probe capacitor and of the reference capacitor. The voltage differential between the probe capacitor and reference capacitor are actively nulled to nominally eliminate a parasitic capacitance therebetween.

Abstract: A capacitance measurement circuit and probe includes a drive circuit couplable to a constant-current source, a threshold detector, a probe capacitor, and a reference capacitor. The circuit includes a plurality of switches being actuatable to alternately couple the current source to the probe capacitor and to the reference capacitor. The drive circuit is configured to alternately generate a signal of linear ramp waveform having a slope that is proportional to the magnitude of capacitance of the probe capacitor and of the reference capacitor. The voltage differential between the probe capacitor and reference capacitor are actively nulled to nominally eliminate a parasitic capacitance therebetween.