Dwyer Capsuhelic. For differential, positive or negative pressures. These gauges are essentially the same construction and dimensions as the G1920 Magnahelic Gauges, but differ in that they can be used at higher temperatures (200F); they can be used at higher pressures (up to 500 psi.); their accuracy is 3% instead of 2%; and except that the pressure being measured is held within a capsule (diaphragm actuated).