Application Data*
34-ST-03-64 Page 15
Liquid Level: Closed Tank Determine the minimum and maximum pressure differentials to be measured (Figure 18).
PMin = (SGp x a) – (SGf x d)
=LRV when HP at bottom of tank
=
PMax = (SGp x b) – (SGf x d)
=URV when HP at bottom of tank
=
Where:
Minimum level at 4 mA
Maximum level at 20 mA
a = distance between bottom tap and minimum level
b = distance between bottom tap and maximum level
d = distance between taps
SGf = Specific Gravity of capillary fill fluid (see page 11 for values)
SGp = Specific Gravity of process fluid
Max
Level
b
Min
Level
a
Transmitter above datum
Max
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Transmitter at datum
Max
Level
b
Min
Level
a
Transmitter below datum
LP
HP
LP
HP
LP
HP
24253
Figure 18—Closed tank liquid level measurement distances.
*Contact