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Chapter 3 Starting and Stopping this Device
(5) Calculation Example Using the JTH Model
Calculation of the setting range is described below.
In this calculation, density and distance are represented by the following symbols. In addition,
density is assumed to be constant during liquid level measurement.
ρ: Specific gravity of liquid in tank
ρ
0
: Specific gravity of sealed liquid
l: Distance between the 100% liquid level and the 0% liquid level (measurement range)
h: Distance between the 0% liquid level and the high pressure side output port
d: Distance between the high pressure side output port and the transmitter
100% Liquid Level
0% Liquid Level
Process
Connection Flange
Open Tank
Figure 3-17. Open Tank
0% liquid level differential pressure
LRV = h×ρ+d×ρ
0
100% liquid level differential pressure
URV = l×ρ+h×ρ
= (l+ h)×ρ+ d×ρ
0
Accordingly,
Low limit (LRV): hρ+d×ρ
0
High limit (URV): (l+h)ρ+dρ
0
is the range to set.
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