Sensors Products Page 15 Applications

15 hamlin.com littelfuse.com When provided with a float magnet, reed sensors can function as fluid-level sensors. For example, in a dishwasher, a float-type level sensor is used to detect if the water level inside of the water collection pan has reached the fill limit. The float sensor consists of a reed switch mounted within a shaft and a permanent magnet provided within a float housing. The shaft is vertically mounted within the water collection pan so that the reed switch is positioned at the water fill limit of the pan. As the water level rises, the magnet within the float travels up the shaft to the point where it comes into the proximity of the reed switch. The reed switch senses the presence of the magnet and signals the dishwasher's ECU that the water level has reached its fill limit. Level sensors incorporating reed switch technology are low-cost solutions for any application where there is a need to detect the amount of liquid in a tank or pan. They are commonly used in white goods and appliances. LEVEL SENSING- Dishwasher Water Level S N ECU Cold Water Valve Hot Water Valve User Interface Reed Sensor Floating Magnet Pump Control Temp Sensor Figure 8-Float sensor detecting water level in a dishwasher to operate the switch actuation hermetically sealed capsule that is immune to moisture, dust and dirt adequate for use in hot and cold temperatures against mechanical stresses and vibration of open/close operations Similar Applications: Dish washers, washing machines, air conditioners, dehumidifiers and coffee brewers A flow switch utilizes a reed switch to detect the motion of a valve, paddle wheel or piston that is fitted with a permanent magnet. For example, in some tankless water heater units, the flow sensor contains a permanent magnet that is fixed to a piston that moves when there is water pressure present in the system. As the water pressure increases, the piston movement brings the magnet into the proximity of the reed switch. This causes the reed switch to close and signals the presence of water flow. A flow sensor utilizes a turbine with an attached magnet that rotates by a fixed reed switch or Hall effect sensor. The speed at which the turbine rotates is proportional to the flow rate of the fluid. Reed sensors are highly effective solutions for flow-sensing applications where there is a need to detect the presence of liquid or gas flow in a system. Common uses include water or gas flow in the similar applications listed. FLOW SWITCH- Tankless Water Heater User Interface Power Circuit ECU Outlet Inlet Water Flow Ignition Circuit Reed Sensor N S N S Figure 9-Flow detection in a tankless water heater to operate the switch actuation adequate for use in hot and cold temperatures hermetically sealed capsule that is immune to moisture, dust and dirt additional protection against mechanical stresses of open/close operations Similar Applications: Dish washers, washing machines, hot tubs and utility gas meters Features and Benefits: Suggested Products: Features and Benefits: Suggested Products:

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