WISE CONTROL INC : Indicating type differential pressure switch with bellows element_P640 series(P641, P642)
Differential switch type A 4P 40A 30ma
Dwyer ADPS-03-2-N Series ADPS HVAC Adjustable Differential Pressure Switch, Set Point Range 0.20 to 2.00"WC, M20 Connection : Amazon.ca: Industrial & Scientific