Questions: Level instruments, advanced c 2002-2003 Tony R. Kuphaldt Copyright ° • Learning Objectives: • How to calculate differential pressure transmitter range values for level measurement scenarios with elevated or suppressed transmitters. • How to develop calibration tables for any level measurement scenario, given an allowable percentage of span error. • How to calculate differential pressure transmitter range values for level measurement scenarios with wet legs. • Identify the potential problem associated with locating a liquid pressure transmitter above the process connection. • How to calculate differential pressure transmitter range values for level measurement scenarios with remote seals. • How to calculate differential pressure transmitter range values for level measurement scenarios with gas and liquid purge. • Develop calibration tables for displacer-based level transmitters. • How to calculate differential pressure transmitter range values for level measurement scenarios with interfaces of two different liquids. • Identify volume measurement nonlinearities caused by vessel shape.
Question 1 Determine the lower and upper range-values for the differential pressure transmitter being used here to measure water level, in pressure units of inches water column (”W.C.). Assume a measured variable span of 40 feet:
100%
Measurement span = 40 ft Water H
L
0%
Question 2 Determine the LRV and URV points for a transmitter measuring water level in the same vessel, but this time located 10 feet beneath the vessel: 1