The capacitive sensor is the nearby sensor that detects objects near the field of electrical energy generated by sensors. Simple capacitive sensors may have been commercially available for many years while the non-metalic object has detected an identification location, but is limited to a near-field model normally less than 1cm.
A capacitive sensor acts behave like a simple capacitor. A metal plate in the sensor surface is electrically connected to an internal oscillator circuit, and the target to be detected acts as the second plate of the capacitor. Not like an inductive sensor that generates an electromagnetic field, a capacitive sensor generates an electrostatic field.
External capacitance between the target and the internal sensor plate shows part of the feedback capacitance of the oscillator circuit. As the target arrive to the sensors, the vibrations increase until they reach a threshold and activate the output.
These capacitors are built with conductive measuring electrodes in a dielectric, with excitation voltages on the order of 5 volts and disclosure circuits that can change the capacitance into a voltage, frequency, or pulse width variation. Applications of capacitive sensors are remarkable.
These are some general applications of capacitive sensors
• Pile up controlling
• Level control of solids
• Small vessel pump control
• Pharmaceuticals manufacturing
• Pipe line and vessel leak detection