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Floating Contact Null Switch for High and Low Actuation

Series 1640

The unique electric switch design in the 1640 is another Dwyer Instrument, Inc. innovation. The Dwyer® Model 1640 Differential Pressure Switch resembles the Series 1630 switches. However, the Model 1640 is equipped with a single pole, double throw floating contact switch (not snap acting) so it functions as a null switch. Drawing 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 example of usage is to position motorized dampers when static pressure in a duct system reaches a desired maximum and reposition the dampers when the static pressure falls to a pre-established minimum. By using a Pitot tube sensing element the Model 1640 switch can serve in the same way to control air velocity and maintain a constant volume of air in a supply duct.

  • Service: Air and non-combustible, compatible gases
  • Wetted Materials: Consult factory
  • Temperature Limits: -30 to 110°F (-34.4 to 43.3°C)
  • Pressure Limits: 10 psig (68.95 kPa) continuous, 25 psig (172.4 kPa) surge
  • Switch Type: Single-pole double throw (SPDT) floating contact (not snap action)
  • Electrical Rating: Non-inductive: 2.5 A @ 110 VAC, 1.5 A @ 220 VAC, 1 A @ 24 VDC, 0.5 A @ 110 VAC; Inductive: 1 A @ 110 VAC, 0.5 A @ 220 VAC, 0.5 A @ 24 VDC. (De-rate 70-80% for very slow pressure changes.)
  • Electrical Connections: 3 screw type, common, normally open and normally closed
  • Process Connections: 1/8" female NPT
  • Mounting Orientation: Diaphragm in vertical position. Consult factory for other position orientations
  • Set Point Adjustment: Screw type
  • Weight: 4 lb 13 oz (2.18 kg)
  • Agency Approvals: CE.




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