The unique electrical switch design in the 1640 series floating contact zero-position switches for high and low actuation is another innovation from Dwyer Instruments. The Dwyer 1640 differential pressure switch is similar to the high-precision large-diaphragm 1630 series switch. However, the 1640 model comes with a single-pole, double-throw floating contact switch (not snap-acting), so it has the function of a deadband switch.  

When the pressure changes, the diaphragm moves, shifting the floating contact to trigger the switch, but movement between the two set points does not trigger any switching. When the differential pressure rises to the set point, the 'high' circuit closes. When the differential pressure falls to the set point, the 'low' circuit closes. The 'low' circuit closes when the differential pressure drops to the preset level.

● The floating "empty" switch supports applications that need two setpoints, like turning the damper control on and off

● The visual setpoint indicator makes operation and troubleshooting easier

● The large diaphragm provides low-range accuracy for precise control