Series 1640 Floating Contact Pressure Switch

Brand: Dwyer Instruments, LLC

The unique electric switch design in the Series 1640 is another Dwyer Instrument, Inc. innovation.

The Dwyer® Series 1640 Differential Pressure Switch resembles the Series 1630 switches. However, the Series 1640 is equipped with a single pole, double throw floating contact switch (not snap acting) so it functions as null switch. 

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 Series 1640 switch can serve in the same way to control air velocity and maintain a constant volume of air in a supply duct.

  • Floating "null" switch supports applications requiring two set point actions such as open and close damper control
  • Visible set point indicator simplifies operation and trouble shooting
  • Large diaphragm provides low range accuracy providing precise control


Adjustment Type

  • Factory Set (Pre-Set)
  • Field Adjustable

Approvals & Certifications

  • CE

Electrical Connectors

  • 3 Screw Typical

Electrical Contacts

  • Normally Closed
  • Normally Open

Electrical Rating

  • Inductive: 1 A at 110 Vac, 0.5 A at 220 Vac, 0.5 A at 24 Vdc (De-Rate 70 % to 80 % for Every Slow Pressure Changes)
  • 2.5 A at 110 Vac, 1.5 A at 220 Vac, 1 A at 24 Vdc, 0.5 A at 110 Vac

NPT Connection

  • 1/8” NPT Female

Operating Temperature

  • -34° for Dry Air or Gas to 43° C (-30° to 110° F)

Proof Pressure

  • bar: 1.7
  • kPa: 172.37
  • psig: 25

Set Point - Decreasing

  • Inches WC: 0.01 to 12
  • kPa: 0.005 to 3

Set Point - Increasing

  • Inches WC: 0.01 to 12
  • kPa: 0.005 to 3

Standard Features

  • Weatherproof

Switch Type

  • SPDT

System Pressure

  • bar: 0.68
  • kPa: 68.95
  • psig: 10


  • 4 lb 13 oz. (2.18 kg)

  • Damper Positioning
  • Duct Air Control
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