Operation of the Transmitter Yamatake Corporation
5-52 ST3000 Smart Transmitter Series 900 Electronic Differential Pressure/Pressure Transmitter
Set range calculation Ex. STC Type
Calculate the set range using these procedures:
The following symbols are used to express density and distance.
It is assumed that the density is fixed, during liquid level measurement.
: Specific gravity of liquid in tank
l : Distance between 100% liquid level and 0% liquid level (measurement range)
h : Distance between 0% liquid level and high-pressure outlet port
d : Distance between high-pressure outlet port and transmitter
Figure 5-9 Open Tank Figure 5-10 Closed Tank
Differential pressure at 0% liquid level (Pressure on high-pressure side - Pressure on
low-pressure side) = h = LRV
Differential pressure at 100% liquid level (Pressure on high-pressure side - Pressure
on low-pressure side) = l + h = (l+h) = URV
Therefore, set the range as follows:
Low limit (LRV): h ; High limit (URV): (l+h) r
Example of calculation:
l = 1500 mm, h = 250 mm
= 0.9, = 1.0
If the above conditions are assumed, the following results are obtained:
Differential pressure at 0% liquid level = (250 x 0.9) = 725 mmH
2
O = 7.110 kPa
Differential pressure at 100% liquid level = {(1500 + 250) x 0.9) = 2075 mmH
2
O =
20.35 kPa
Therefore, set the range as follows:
Low limit (LRV): 7.110 kPa{725 mmH
2
O}, High limit (URV): 20.35 kPa{2075
mmH
2
O}
ρ
h
ρ
100% liquid level
0% liquid level
Tank
Open to air
h
P
ρ
100% liquid level
Tank
0% liquid level
Blow valve
Volume container
Stop valve
ρ
ρρ ρ
ρ
ρρ
0
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