Float Switches
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The Comus Group of Companies The Comus Group of Companies The Comus Group of Companies The Comus Group of Companies Contact Form Most switch actions on our Float Switches can be changed from Normally Open to Normally Closed by refitting and reversing the float on its stem. See individual specifications for details. For cable tether type floats specification on the contact type required (Normally Open or Normally Closed) should be given by the customer, in order for us to supply the correct type for your application. Normally Open and Normally Closed refer to the switches position at rest in a dry tank. Specific Gravity Specific Gravity (SG) is the ratio of an objects density in relation to that of water. Water has a specific gravity of 1 when at sea level. Liquids or substances with a specific gravity lower than 1.0 will float in water. It is important to select the correct float switch and float for your application. For example a float switch with a specific gravity of 0.8 will float well in water but will sink in alcohol which is around 0.72 SG. Our sales office will be pleased to assist you with your application, and establish whether a custom floating magnet is required. The table on the reverse of this catalogue may be used for reference. SPECIFIC GRAVITY Overleaf you will find our most common types of Float Switches available. If you require something different to those shown (longer length vertical or horizontal stem or longer cable length), then simply ask our sales office who will be pleased to help you with your application. Material Selection Stainless Steel: Ideal for high pressures, high temperatures and in corrosive environments such as food equipment, industrial tanks or where durable long ife in general use is required. General Use Plastics: Polypropylene, PVC and Polycarbonate are a good choice for use in acids or food applications, or just for general use. They are generally the most economic option, and can be easily custom moulded with additional features for OEM applications. Multi-Level Float Switches Aside from the Float Switches overleaf, we are also able to offer multi-level float switches where switching at multiple levels is required. These are all fully customizable to your specifications. We are also able to offer Stainless Steel Float kits. These DIY Float kits have been designed to enable easy construction of a prototype or small quantity of switch assemblies and come with housings, Stainless Steel tubes, union connectors, floats, and reed switches. We can also provide an assembly service if required. If you cannot find what you require for your application, please speak to our sales office, who will be pleased to listen to your requirements, and offer you a solution. Float Switches DESCRIPTION Reed Float Switches are designed to fit into tanks or containers containing liquid. They are operated by a magnet fitted into the float assembly and a Reed Switch fitted into the stem of the float body. When the float moves past the Reed Switch inside the float body, the reed contacts operate (open or dose). When the float moves back to its original position the reed switch contacts will also return to their orginal state. In conjunction with a pump, this principle allows control over the liquid level. The cable tether type float switches use either Mercury or a Mercary free contact in place of a Reed Switch, and it is the differential angle of the Tilt Switch inside the float that determines the point at which the contacts wil operate (open or dose). CONTACT PROTECTION Lamp Loads Inductive Loads A reverse voltage is generated by stored energy in an inductive load when reed contacts open. This voltage can reach very high levels and is capable of damaging the contacts. An RC network may be used as shown below to give protection. With lamp load applications it is important to note that cold lamp filaments have a resistance 10 times smaller than already glowing filaments. This means that when being turned-on, the lamp filament experiences a current flow 10 times greater than when already glowing. This high inrush current can be reduced to an acceptable level through the use of a current-limiting resistor. Another possibility is the parallel switching of a resistor across the switch. This allows just enough current to flow to the filament to keep it warm, yet not enough to make it glow. The Comus International group of companies consists of: Side Mounting Vertical Mounting Comus International 454 Allwood Road Clifton New Jersey 07012 U.S.A Tel: (1)973 - 777 - 6900 Fax:(l)973 - 777 - 8405 email: info@comus-intl.com Website: http://www.comus-intl.com Assemtech Europe Limited Unit 7, Rice Bridge Industrial Estate Thorpe - Le - Soken Essex England COI6 0HL Tel: +44 (0)1255 862236 Fax: +44 (0)1255 862014 email: sales@assemtech.co.uk Website: http://www.assemtech.co.uk Comus Belgium BVBA Overhaamlaan 40 B-3700 Tongeren Belgium Tel: +32 (0)12 390400 Fax: +32 (0)12 235754 email: info@comus.be Website: http://www.comus.be Capacitive Loads Unlike inductive loads, capacitive and lamp loads are prone to high inrush currents which can lead to faulty operation and even contact welding.When switching charged capacitors (including cable capacitance) a sudden unloading can occur, the intensity of which is determined by the capacity and length of the connecting leads to the switch. This inrush peak can be reduced by serial resistors. The value is dependent on the particular application but should be as high as possible to ensure that the inrush current is within the allowable limits. Lamp load with parallel or current limiting resistor across the switch Switch Ratings The load switching capacity of most float switches can be significantly increased with the addition of Relay Units, ask our sales office for details. Cable Tether Comus Electronics and Technologies India Private Limited No 26. Crescent Park Street T Nagar Chennai 600 017 India Tel: +91 44 42127124 Fax: +91 44 42127125 email: syed@comus-intl.com venkataraman@comus-intl.com Website: http://www.comusindia.com The above diagram illustrates a resistor/capacitor network for protecting a Reed Switch against high inrush currents. R| and/or R2 are used depending upon circuit conditions. All dimensions are nominal, in millimetres unless otherwise stated. If further information is required, individual datasheets are available on our websites, and on CD. As part of the groups policy of continued product improvement, specifications may change without notice. Our sales office will be pleased to help you with the latest information on our products. We also have a large network of worldwide agents. These can be seen on any of our websites, or on our company profile brochure. All dimensions are nominal, in millimetres unless otherwise stated. If further information is required, individual datasheets are available on our websites, and on CD. As part of the groups policy of continued product improvement, specifications may change without notice. Our sales office will be pleased to help you with the latest information on our products.