Regulators

Direct operated regulators are the simplest style of regulator. At lower pressures (below 1 psig) they can have very accurate control. At high pressures (up to 500 psig) 105 - 20% is typical. 
In operation, a direct operated pressure regulator senses the downstream pressure through either internal pressure registration or an external control line. this downstream pressure opposes a spring which moves the diaphragm and calve plug to change the size of the flow path through the regulator.