Differential pressure gauges measure difference in pressure
These Orange Research differential pressure gauges from Cameron Instruments are designed to measure the difference in pressure between two points in a system and present the resultant differential pressure directly on a single gauge dial. A magnetic movement allows the simultaneous sensing of both pressures while completely isolating the differential pressure gauge function from the pressure chamber without the use of mechanical seals. They can indicate small values of differential pressure even when used at high line pressures. They include reed switches or relays to initiate alarms, activate other equipment, or shut the system down. Two switches are installed when high and low limit control is desired.