Capacitive
proximity switches also operate contactless and equally respond almost instinctively
when conductive or non-conductive materials in solid, powdery or liquid states
have to be measured. They are particularly convincing in monitoring fill levels
through non-metallic materials such as plastic or glass, and in counting objects
made of various substances.
Highlights
Detection of all materials (e.g. plastic, wood, paper)
Measurement of liquid through plastic tubes or glass pipes
Measurement of aggressive chemicals
Adjustment of the operating distance on the object
Function
The sensing face of a capacitive sensor is formed by two concentrically arranged
metal electrodes that are equivalent to the electrodes of an unwound capacitor.
The electrode surfaces A and B are connected into the feedback branch of a high-frequency
oscillator that is tuned such that it does not oscillate when the surface is free.
When an object approaches the active face of the sensor, it enters the electric
field in front of the electrode surfaces and causes a change in the coupling capacitance.
The oscillator starts to oscillate; the amplitude is recorded by an evaluation
circuit and converted into a switching command.
Switching frequency
The build-up characteristics specific to other pulse/interval conditions may result
in higher switching frequencies than those specified.
Operating distance
The stated values are applicable to a target of metal which is grounded and whose
area corresponds to the sensing face of the proximity switch. The real operating
distance sr for nonconductive targets is dependent on the relative dielectric
constanter and the characteristic value (see characteristic curve).
Capacitive
proximity switches also operate contactless and equally respond almost instinctively
when conductive or non-conductive materials in solid, powdery or liquid states
have to be measured. They are particularly convincing in monitoring fill levels
through non-metallic materials such as plastic or glass, and in counting objects
made of various substances.
Pre sales info
Applications
Overview Proximity Switches