Differential pressure regulators and valves are used in applications to maintain a constant (and specific) pressure differential between the outlet (P2) pressure of the regulator and the signal pressure loaded on the diaphragm. The desired differential can be set with a spring and an air sense line can be added to the dome of the regulator to constantly follow the pressure up and down, while always maintaining the same difference in pressure.

Negative bias pressure regulators and valves operate the same way, except the spring is placed into a state of tension instead of compression.