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Proximity Sensors/Operating Principle/Type |
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Outline |
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A proximity sensor can detect metal targets approaching the sensor, without physical contact with the target. Proximity sensors are roughly classified into the following three types according to the operating principle: the high-frequency oscillation type using electromagnetic induction, the magnetic type using a magnet, and the capacitance type using the change of capacitance.
KEYENCE proximity sensors are of the high-frequency oscillation type.
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Features |
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Non-contact detection, eliminating damage to sensor head and target. |
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Non-contact output, ensuring long service life. |
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Stable detection even in harsh environments exposed to water or oil splash. |
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High response speed. |
Operating Principle of High-frequency Oscillation Type Proximity Sensor |
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Operating principle of general sensor |
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A high-frequency magnetic field is generated by coil L in
the oscillation circuit. When a target approaches the
magnetic field, an induction current (eddy current) flows
in the target due to electromagnetic induction. As the
target approaches the sensor, the induction current flow
increases, which causes the load on the oscillation
circuit to increase. Then, oscillation attenuates or stops.
The sensor detects this change in the oscillation status
with the amplitude detecting circuit, and outputs a
detection signal.
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Aluminum Proximity Sensor |
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| Generally, the frequency of high-frequency, oscillation type proximity sensors tend to change when a nonferrous metal is placed near it. The aluminum proximity sensor detects any changes in oscillating frequency. |
Type |
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Classification by configuration |
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Standard configuration |
Features |
| Self-contained proximity sensor |
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Readily operative by adding DC power supply. |
| Separate/In-cable amplifier |
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Compact sensor head
Long-detecting distance |
Glossary |
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| Shielded type |
Non-shield type |
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The sensing coil is encased in a metal-shielding.
This type is less affected by surrounding metal, and can be embedded in a metal base. |
The sensing coil is not metal-shielded.
This type provides a longer detecting distance, compared to a shielded type of the same size.
This type is easily affected by surrounding meta, and therefore no object other than the target must be present around the tip of the sensor head. |
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