DESCRIPTION
Capacitive sensors are used to detect metallic and non-metallic objects (liquid, plastic, wooden materials and so on). These capacitive sensors have a normally open or normally closed output selector switch and operate on a wide voltage range, 20 - 250 V AC/DC. This greatly reduces the need to keep multiple sensors in stock. These models are also not polarity sensitive so there is no complicated wiring or a need to reverse wiring to change the output.
Their housing consists of a cylindrical threaded metal or plastic 30 mm diameter case. They are dust and water tight as well as shock and vibration resistant. All models feature LED indication of the output status and short circuit protection up to 50V in DC.
A screw placed on the sensor allows regulation of the operating distance. This sensitivity regulation is useful in applications, such as detection of full containers and non-detection of empty containers.
A waterproof protective housing is available. This housing is made of a non-toxic material (POM) and has a standard 1 1/2" GAS threaded fitting for mounting into a container. This housing permits a sensor to be rapidly removed for testing without the loss of material and protects the sensor from abrasion. The use of the housing can help to eliminate variation in the sensitivity of the sensor due to deposits of material.
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OPERATING PRINCIPLE
Capacitive proximity sensors use the variation of the parasitic capacity that develops between the sensor and the object being detected. When the object is at a preset distance from the sensitive side of the sensor, an electronic circuit inside the sensor begins to oscillate. The rise or fall of such oscillation is identified by a threshold circuit that drives an amplifier for the operation of an external load.
The operating distance of the sensor depends on the actuator shape and size and is strictly linked to the nature of the material (Table 1.).
| Table
1. Sensitivity when different materials are present. Sn = operating
distance. |
| Metal |
~ 1 x Sn |
| Water |
~
1 x Sn |
| Plastic |
~
0.5 x Sn |
| Glass |
~ 0.5 x Sn |
| Wood |
~
0.4 x Sn |
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Data sheet
