Capacitive proximity sensors are triggered by a change in the surrounding dielectric.  The transducer of a capacitive sensor is configured to act as the plate of a capacitor.  The dielectric property of any object present in the sensing field increases the capacitance of the transducer circuit and, in turn, changes the frequency of an oscillator circuit.  A detector circuit senses this change in frequency, and signals the output to change state.
 

• CQ28
• CM18
• CM30
• CQ35
• CM30AC
• CM18PTFE