Pressure controllers are used to control positive or negative (vacuum) pressure. Inputs from pressure sensors are received, regulated and produce  output control signals. Pressure regulators employ a variety of control types. Controlling the limits by cutting off power to a load circuit when pressure rises above or decreases below a preset point protects the equipment from damage. Non-linear control techniques like adaptive gain, dead-time compensation, and feed-forward control are used for advanced controls. Linear controls use proportional, integral, and derivative (PID), proportional and integral (PI), proportional and derivative (PD), or proportional (P) control.

Barometric pressure is simply atmospheric pressure.