Introduction

The series SW 505 Capacitive Proximity Switches are designed for sensing wide range of materials. These switches give a superior performance for detection of various non-metallic objects where Inductive type switches can not function.

The major applications of Capacitive Switches include sensing of

• Liquid level
• Plastic granules & parts
• Sand / Bulk Material Level
• Food / Grain / Confectionery
• Paper & rubber
• Glass bottles / Tins in packaging

Working Principle

The switch works on the principle of resonant oscillator circuit. A pair of brass/copper disc from 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 tabular 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

Effect of Ambient Conditions on Sensitivity

The sensing distance is affected by change in ambient temperature, humidity, size and material of the object.

General Specifications

Operating Temperature	:	55°C Max.
Response Time	:	2 to 5 milliseconds
Hysteresis	:	3% to 15% of actuating point
Protection Grade	:	IP-67
Quiescent Current	:	1) DC - 8 mA Max. 2) AC - 2 mA Max.
Indication	:	LED for object status
Output	:	1) To drive a Relay 2) PLC Compatible

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.

Protection

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.

Protection

Type	Ordering Code	Supply	Mounting	Dimensions	Sensing Distance
Capacitive	SW 5051 PO D1 BF18 SW 5051 PO D1 BF12 SW 5052 NC D4 BF12 SW 5053 NO D6 BF12 SW 5055 NO A2 BF12 SW 5055 NO A3 BF12	10-30 V DC 10-30 V DC 8.5 V DC 24 V DC 110 V DC 240 V DC	Non Flush Non Flush Non Flush Non Flush Flush Flush	M18 * 85 M18 * 85 M30 * 65 M18 * 85 M24 * 85 M18 * 85	2-10 mm 3-15 mm 3-15 mm 2-10 mm 1-5 mm 2-10 mm