Historical
NFPA/T2.12.1 R1-2002 (R2009)
Hydraulic fluid power - Systems and products - Method of measuring average steady-state pressure [to be used in conjunction with NFPA/T2.12.10]
This standard is limited to the measurement of average steady-state static pressure in a closed conductor that meets the following criteria: must be transmitting hydraulic fluid power; average fluid velocities are less than 25 meters per second (82 ft/sec); average steady-state static pressure is less than 70 Mpa (10,000 psi); inside diameters are greater than 3.0 millimeters (0.120 in); sensor is not flush-mounted with, or an integral part of, the closed fluid conductor wall.
National Fluid Power Association [nfpa-fluid]