Using inductive proximity sensors to measure displacement.

You could try an analog Hall effect sensor - place a magnet so that as the steel moves it channels more magnetic flux though the sensor. If you sketch out the geometry of the shaft movement I can indicate where to place the sensor and magnet.

You can also use a capacitance sensing technique - set up two electrode pads (capacitor plates) near the steel shaft such that as the shaft moves it gets closer to one or both pads - this will effectively reduce the "distance" between the plates an the capacitance between them will increase. This method has the drawback that anything else nearby may affect the reading.

You could try an analog Hall effect sensor - place a magnet so that as the steel moves it channels more magnetic flux though the sensor. If you sketch out the geometry of the shaft movement I can indicate where to place the sensor and magnet.

You can also use a capacitance sensing technique - set up two electrode pads (capacitor plates) near the steel shaft such that as the shaft moves it gets closer to one or both pads - this will effectively reduce the "distance" between the plates an the capacitance between them will increase. This method has the drawback that anything else nearby may affect the reading.

Hello I wanted to ask If I can measure the distance of a metallic indictor plate by the inductive sensor? Can the sensor be used where asphalt is used? I have checked few inductive sesnors which operate at more than 160 degrees centigrade. But what would be the affect of temperature fluctuation in the measurement?

Buried inductive sensors are used at road intersections to detect vehicles in the turning lane. They would need to be built with wire that has high temperature insulation for your application. The signal level would be proportional to the size of the plate, its material, its shape and its distance. Think of a metal detector circuit...

I need to measure the changing distance.So ideally i want the distance to be 0.50 mm but due to wear the distance increases.So the purpose is to measure the distance upto the metallic indiactor , if its 1 mm that measn i have to reduce the gap by 0.50 mm.The inductive sensor will sense the distance and actuate the hydraulic cylinder for adjusting the gap. But this mechanism is all in a screed of the paver whch is heated and also there are hot fumes from the asphalt. Is an inductive sensor here a right option?

For a small distance like that, a capacitance sensor should work well.

What would be the problems of using an inductive sensor in my application? Its just a part of investigation so I would like to know.

Each technology has pros and cons depending on many factors, like materials and geometry. Induction probably involves more complex circuitry. Both are fairly straight forward in theory but both will be difficult to calibrate and both will be take some work to achieve accuracy with.

Thanks for you response on inductive sensors. Can you also give me some information on laser displacement sensors ? If they could be used to measure the gap?