Transmitter Calibration Range of a Vessel Level

The following storage vessel holds liquid heptane, a hydrocarbon with an approximate specific gravity of 0.68.

A pressure transmitter located at the bottom infers heptane level by hydrostatic pressure (head).

Determine the calibration range of this pressure transmitter in order to properly translate the range of vessel level (0 to 14 feet) into an output signal of 4 to 20 mA.

Transmitter Calibration Range

Please express the transmitter’s calibration range in units of inches W.C. (inches of water column).

Then, determine the following (assuming the transmitter has been properly calibrated for the application):

Transmitter output signal (mA) at 8 feet of level

Heptane level at 5.7 mA signal output

Answer

Lower range-values (LRV): 0 inches W.C. input = 4 mA output

Upper range-values (URV): 114.24 inches W.C. input = 20 mA output

Transmitter output signal (mA) at 8 feet of level = 13.14 mA

Heptane level at 5.7 mA signal output = 1.4875 feet

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Credits: Tony R. Kuphaldt