Instruction Manual
D200124X012
2500 and 2503 Controllers/Transmitters
June 2017
22
To determine the total weight that must be suspended from the displacer rod to simulate a certain condition of fluid
level or specific gravity, solve the following equation:
W
s
+
W
d
–
ƪ
(0.0361)(V)(SPGR)
ƫ
where:
W
s
= Total suspended weight in pounds (should never be less than 0.5 pounds). For a unit with a horizontal displacer,
make sure the center of gravity of the substitute weight is where it would be on the actual displacer.
Note
For liquid level control only, simulate the lower range limit of the input span by suspending the displacer from the displacer rod.
For other values of input span, remove the displacer and suspend the appropriate weight as determined in the equation above.
W
d
= Weight of the displacer, in pounds (determine by weighing displacer).
0.0361 = Weight of one cubic inch of water (specific gravity = 1.0), in pounds.
V = Volume, in cubic inches, of the portion of the displacer submerged. Or,
V =
(π
/4) (displacer diameter)
2
(length of displacer submerged)
SP GR = Specific gravity of the process fluid at operating temperature.
For interface level measurement, the equation becomes:
W
s
+
W
d
–
ƪ
(0.0361)(V
t
)
ǒ
SPGR
l
Ǔ )
(0.0361)
ǒ
V
h
Ǔǒ
SPGR
h
*
SPGR
l
Ǔ
]
where:
V
t
= Total volume, in cubic inches, of the displacer.
SP GR
l
= Specific gravity of the lighter of the fluids at operating temperature.
V
h
= Volume, in cubic inches, of the portion of the displacer submerged in the heavier of the fluids.
Or,
V =
(π
/4) (displacer diameter)
2
(length of the displacer submerged)
SP GR
h
= Specific gravity of the heavier of the fluids at operating temperature.
Calibration Procedure
WARNING
The following calibration procedures require taking the controller/ transmitter out of service. To avoid personal injury and
property damage caused by an uncontrolled process, provide some temporary means of control for the process before
taking the controller/transmitter out of service.
