Inductive
Proximity sensors find wide application in the field of industrial
instrumentation. These sensors are extremely popular as they are
reliable, robust and have a simple construction. Inductive Proximity
sensors are used to measure speed, detect motion and sense the position of
objects.
The inductive proximity sensor consists of an oscillator, a coil and a detector. The oscillator develops a high frequency signal which is fed to the coil.
The inductive proximity sensor consists of an oscillator, a coil and a detector. The oscillator develops a high frequency signal which is fed to the coil.
The high frequency signal develops a corresponding high
frequency magnetic field at the tip of the sensor. When a metallic object
comes in front of the sensor, eddy currents are induced in the object.
This acts as a load on the oscillator and the amplitude of the high frequency
output drops. This drop in the voltage is detected by the detector unit
which causes the switching on or off of a transistor. This results in a
change of voltage level which is interpreted as a digital signal 0 or 1.
The inductive proximity principle can also be applied to
speed sensors. In speed measurement, the inductive proximity sensor is
placed near the rim of a rotating object. The rotating object has a number of
teeth along its rim. When a tooth passes near the inductive proximity
sensor, a pulse is produced.
This sequence of pulses can be converted into an analog signal can be measured as the speed of the device.
This sequence of pulses can be converted into an analog signal can be measured as the speed of the device.
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