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| Introduction |
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Capacitive Sensors:- Capacitive Proximity Switches are offered in the widest range of sizes, with
variety of function options. Capacitive Sensors have unique ability to detect metallic as well as non- metallic objects. The Capacitive Proximity Switches give a superior performance for sensing various non-metallic objects, not detected by Inductive Proximity Switches.
The Capacitive Proximity Switches work on the principle of resonant oscillator circuit. a pair of brass/copper discs form electrode of a capacitor and the object acts as a dielectric media. The change in capacitance value is sensed by a precision integrated circuit. An effective output signal is generated at a preset value of capacitance.
These are offered in tubular threaded housing from size M12 to M60. The enclosures are made of brass, stainless steel or engineering plastics.
Introduction- series-SW 505:- The Series SW 505 Capacitive Proximity Switches are designed for sensing wide range of materials. These switches give a superior performance for detection The Series SW 505 Capacitive Proximity Switches are designed for of various non-metallic objects where Inductive type switches can not function. The major applications of Capacitive Switches include sensing of:- 1) Liquid level. 2) Plastic granules & parts. 3) Sand / Bulk Material Level.
4)Food / Grain / Confectionary. 5) Paper & rubber 6) Glass bottles/ Tins in packaging
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Working Principle:- The switch works on the principle of resonant oscillator circuit. A pair of brass/copper disc form the electrodes of a capacitor & the object acts as a dielectric media. The change in capacitance value, due to presence of object, is sensed by a precision integrated circuit. An effective output signal is generated at a preset value of capacitance.
Construction:- These are offered in tubular threaded housing from size M12 to M80. The enclosures are made of Brass, Stainless Steel or Engineering Plastics. Special shapes, Teflon housings are provided against requirements. Standard models are provided with an integrated 2 meter long cable. Connector type versions are available with built-in male connectors.
Sensing Distance:- The nominal sensing distance of any size of switch is specified with Water as standard object and tested at 25°C.Depending upon the material of the object to be detected, the distance will vary. The sensitivity of the sensor is adjustable with a trimpot provided usually on the rear side of the sensor. Typical Sensing distance chart for a M30 size sensor, for different objects is shown in Fig-1.
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| Sensing Distance for various materials |
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Effect Of Ambient Conditions On Sensitivity:- The sensing distance is affected by change in ambient temperature,
humidity, size and material of the object. |
Common Specifications |
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Operating Temperature |
55°C Max. |
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Response Time |
2 to 5 milliseconds |
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Hysteresis |
3% to 15 % of actuating point |
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Protection Grade |
IP-67 |
| Quiescent Current |
1) DC - 8 mA Max.
2) AC - 2 mA Max. |
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Indication |
LED for object status |
| Output |
1) To drive a Relay
2) PLC Compatible |
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Special Models:- Special High Temperature models of Capacitive switches are available with Operating Temperature upto 150°C max. These switches are provided with a teflon front cap and with suitable teflon cable. These switches are to be used with a specially designed controller/amplifier unit. The permitted operating length between sensor and the controller is maximum 5 meters. NAMUR type switches are available with CMRI-Certificate and approved Power Supply Unit with built-in Zener barrier circuit.
Protections:- All the Capacitive switches are provided with Reverse polarity, Overload, short circuit and false pulse protections. Rugged construction along with IP-67 grade of protection renders these switches to be very useful for liquid level monitoring applications. |
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