Dwyer 1640-0

Floating contact null switch, range .01-0.2" w.c., adj. null span, .01 min. set, .03 max. set.
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. The Model 1640, however, is equipped with a single pole, double throw floating contact switch (not snap acting) so it functions as a null switch.