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> Dwyer null switch pressure 1640-1
Dwyer null switch pressure 1640-1
Model 1640 Floating Contact Null Switch for High and Low Actuation
Dwyer Model 1640 Floating Contact Null Switch
is identicalto Dwyer Series 1630 Large Diaphragm Pressure Switches,except for its electric switch. Model 1640 is equipped with a single pole, double-throw floating contact switch (not snap action),so it functions as a null switch.The drawing above shows the switching action schematically. As the diaphragm moves in response to pressure changes, it moves the floating contact to cause switching action at two preset points, with no switching action between these points. The “high†circuit will be closed when rising pressure differential reaches the preset level; the “low†circuit will be closed when falling pressure differential reaches the preset level.A typical usage for this switch is to position motorized dampers when static pressure in a duct system reaches a desired maximum,and to reposition the dampers when the static pressure falls to a pre-established minimum. By using a pitot tube sensing element, Model 1640 can serve in the same way to control air velocity and maintain a constant volume of air in a supply duct.
