Basics Inductive Sensors
Basic Knowledge of Inductive Sensors
Operation area: |
|
Analogue inductive sensors are working based on to the principle of the inductive oscillating circuit. Contrary to the classical switching sensors, these sensors are processing the drawn energy of the electromagnetic field to a steady and almost linear output signal. Because of the internal wiring, analogue sensors are supplying direct or inverse characteristics with current or voltage output. In industrial applications current values of 4 ... 20 mA and voltage values of 0 ... 10 V are usual. With the development of micro controllers in sensors, there are now multiple variations possible in wiring and signal processing.
Operation area: |
|
Ring sensors are using the physical effect of performance change of a resonant circuit that is created by eddy current losses in conductive materials. Because of this, all conductive objects can be detected. An oscillator inside of the sensor creates a high frequency, electromagnetic alternating field. Because of the rotationally symmetric coil arrangement, an almost homogeneous field is generated. The ferrite core and the housing of the sensor are bunching the flux lines of the alternating field in the centre of the ring. If metal enters in the sensor, eddy currents are created which take energy out of the alternating field. Because of this, a damping is caused as well as a change of the voltage in the oscillator. The electronics inside the sensor are evaluating the voltage change.
Digital ring sensors are classified in static sensors (normal sensitivity) and dynamic sensors (high sensitivity). As long as there is metal inside the sensor area, the static sensor is creating a permanent signal. Only if the metal is removed, the signal falls off. Static sensors detect stationary and moving parts. Dynamic sensors are only creating a short pulse when detecting metal. They only detect metal when they are moving in the sensor area, but they work with a much higher sensitivity.
Analogue ring sensors are generating a permanent signal (like static sensors) that depends on the size and situation of the metal in the sensor. The bigger the metal, the bigger the output signal of the sensor.
Operation area: |
|