1640 Floating Contact Null Switch for High and Low Actua...

Visual set point adjustment, adjustable null zone, and functions as a null switch

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$697.00 CAD
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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 a 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.

Caution: For use only with air or compatible gases

• 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


Service Air and non-combustible, compatible gases
Wetted Materials Consult factory
Temperature Limits -30F - 110F (-34.4C - 43.3C)
Pressure Limits 10 PSIG (68.95 kPa) continuous, 25 PSIG (172.4 kPa) surge
Switch Type SPDT
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 in female NPT
Mounting Orientation Diaphragm in vertical position
Set Point Adjustment Screw type
Weight 4 lb 13 oz (2.18 kg)
Agency Approvals CE

• Damper positioning
• Duct air control