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Float Switch Technology  
 
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Every Madison float switch has a float containing a magnet and a dry reed switch encapsulated within a stem. The float travel in the liquid magnetically actuates the reed switch, providing an "on" or "off" function.
Operation (NO/NC)
Switch operation is determined while the switch is in the dry position with the installation fitting up. normally open (NO) normally closed (nc)
Normally Closed: Switch will open on the rise of liquid and close on the fall of liquid.
Normally Open: Switch will close on the rise of liquid and open on the fall of liquid.
Madison switches are supplied in the normally closed (NC) position, unless otherwise specified.

Reed Contact Protection

Every Madison float switch contains a dry reed switch encapsulated within a stem. Reed switches are highly reliable and able to deliver more than 5 million switching cycles when operated at their rated electrical load. To ensure many years of operation, it is important to consider the electrical load conditions to which the switch will be subjected.

All reed switches are rated for resistive loads or steady state current. Devices such as motors, solenoids, coils, strobes or tungsten lights are capable of producing a capacitive or inductive electrical load. When power is applied or removed, these devices can produce a current spike that is four to ten times the steady state current. The resulting exposure to high current can burn the reed switch contacts or fuse the reeds together, causing a shortened switch life or failure.

We recommend that a circuit be used to protect a reed switch from current overload caused by a capacitive or inductive device. The commonly-used circuits shown below will allow the switch to function while preventing high current from damaging the reed switch contacts.

Reed Protection DC Contact Protection/Load Drain Lamp Loads
  Note: For AC loads, the diode can be replaced with a varistor. R = Current limiting resistor
("R" should be selected to give "Is" less than the rated carrying current.)
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