	Displacement Sensors

Inductive (eddy current) displacement

Operating Principle

Inductive displacement sensors utilize a high-frequency magnetic field which is generated by passing a high frequency current through the sensor head coil. When a metal target is present in the magnetic field, electromagnetic induction causes an eddy current perpendicular to the magnetic flux passage to flow on the surface of the target. This changes the impedance of the sensor head coil.
Inductive displacement sensors measure the distance between the sensor head and target, based on this change in oscillation status.

How inductive (eddy current) sensors work

KEYENCE inductive displacement sensors utilize two variations of this operating principle.

EX-500 Series

As the target comes closer to the sensor head, the oscillation amplitude becomes smaller and the phase difference from the reference waveform becomes larger. By detecting changes in the amplitude and phase, the sensor can obtain a value approximately proportional to the change in the distance between the sensor head and target.

Amplitude and phase variations with distance

Based on the target material, values are digitally processed and corrected using a high accuracy linearizer circuit. The linear output is proportional to the distance between the sensor head and target.

[EX-200 Series

As the target approaches the sensor, the eddy current increases and oscillation amplitude becomes smaller. The oscillation amplitude is rectified and amplitude variations are converted to DC voltage variations. With its linearization circuit, the EX-200 Series corrects the output voltage-distance characteristic in order to optimize linearity.

Linearization of analog output voltage

Effective Use

Measures to waterproof the sensor head

Inductive displacement sensor measures the distance between the sensor head and target using a magnetic field, so sensor operation is unaffected by a non-metallic objects. The EX Series sensor is highly water and dust resistant, and is highly resistant to harsh environments. However, the sensor head is not completely waterproof. Therefore, when using the sensor head in a location exposed to water or oil splash, we recommend that the following measures be taken.

Examples of waterproofing methods

About Mutual Interference

If sensors of the same type are placed closely together, the resolution may be affected due to the high-frequency magnetic field of the sensors. This is called mutual interference.

How to prevent mutual interference?

	Use the mutual interference suppression function.(EX-500 series/EX-V series : Keyence)
	Maintain enough distance from other devices to prevent interference. ( See description of the respective model.)
	Combine with a different type sensor. ( EX-200, AS series: Keyence - For more details, please contact us separately. )

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