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How material,size or thickness of detected object affects sensing distance?

Proximity sensor refers to a general term. It is designed to replace the contact detection like limit switches, for the purpose of detecting without touching the object. It works by converting the movement and presence information of the detected object into electrical signals. With characteristics like long duration, reliable operation, high repeat positioning accuracy, no mechanical wear and tear, no sparks, no noise, and strong vibration resistance, it can be used as limit, counting, positioning control and automatic protection in automatic control system.

For the selection of proximity sensors, engineers need to select the models with appropriate range based on the sensing distance requirements. Here, detected objects in different materials, sizes and different thickness will have an impact on the sensing distance of proximity sensor. Let’s share the related information to you in this post.

Part 1 Material

①Attenuation coefficient

The core of the inductive proximity sensors are oscillators and amplifiers that detect objects made of metal.

Generally, the standard detection object on the sensor is iron, and the attenuation factor varies for different metal. For example, stainless steel, aluminum alloy, aluminum, copper, etc. will have different attenuation levels.

It performs as below:

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②Relative Permittivity of Capacitance

Due to the characteristics of capacitive proximity sensor,it can not only detect metal, but also can detect non-metallic objects such as plastic, glass, water, oil and other substances accordingly. When we detect non-metallic objects, the corresponding detection distance is affected by the conductivity, permittivity, volume absorption and other parameters of the detected objects. In particular, the sensing distance and sensitivity are different for those objects with various permittivity. The greater the permittivity of the material is, the greater the sensing distance can be obtained.

The permittivity presents of common materials are as follows:

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Part 2 Thickness

The thickness of magnetic metal (like iron, nickel and etc.) should be more than 1mm.
The foil with thickness less than 0.01mm can get the same sensing distance as that of the magnetic body. In addition, extremely thin materials such as vaporized film and non-conductive objects cannot be detected.
Influence of electroplating: when the object is platted, the detection distance will change. (See the table below)

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Effect of electroplating

(Reference value: % detection distance relative to no plating)

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Part 3 Size

 

Generally speaking, when the size of the detected object is smaller than the standard detected object, the sensing distance will become shorter.
Please follow the chart below to design for objects larger than the standard one.
When the size of the detected object is smaller than the standard one, please make the setting distance with sufficient space.

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+86 0755-23337227

+86 0755-27920807

info@akusense.com

4F-5F, Building A, Tiange Technology Park, No.2 of Luozu Industrial Avenue, Shiyan Street, Baoan District, Shenzhen

Copyright (C) 2021 AKusense All Rights Reserved. Brand Planning: CTM
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