The difference in pressure between two points. The difference may be due to frictional pressure resistance of a flowing fluid, blockage, and obstacles, and for some types of flow meters, it can be used to determine flow rate. The differential pressure can be measured using devices such as manometers. A differential pressure cell is widely used to measure the flow rate in pipes in which the differential pressure measured across an orifice is converted to a pneumatic, electrical, or mechanical signal for transmission to a local controller. See dp cell.