Siemens Sitrans 사용자 설명서
7ML19985GE01
SITRANS LC 500 – INSTRUCTION MANUAL
Page 91
mmm
mm
Appendix E
Applications Examples
Generic Application Calculations
The capacitance expected in a cylindrical tank with a probe centrally mounted is
estimated using the following formula:
estimated using the following formula:
(L in meters) or
(L in feet)
Examples (using dimensions above):
Capacitance in air:
Dimensions in meters:
Dimensions in feet:
Capacitance in oil:
If the same vessel is filled with oil, relative dielectric constant for oil (2) replaces the
relative dielectric constant for air (1), and the resulting calculation is:
relative dielectric constant for air (1), and the resulting calculation is:
(dimensions in meters)
or
(dimensions in feet)
The initial capacitance value at 0% (probe in air) is 12.7 pF, and the capacitance value for
100% (tank filled with oil) is 25.4 pF.
100% (tank filled with oil) is 25.4 pF.
C
ε
24 L
×
Log D d
⁄
(
)
--------------------------pF
=
SITRANS LC 500
0.25 m (0.82’)
L = 0.95 m
(3.12’)
D
= 1.0 m
(3.28’)
d = 16 mm
(0.05’)
Where:
C = capacitance value in pF
ε
r
= relative dielectric constant
L = active measurement length
D = internal tank diameter
d = electrode diameter
24 = a K constant for dimensions in meters
7.32= a K constant for dimensions in feet or inches
D = internal tank diameter
d = electrode diameter
24 = a K constant for dimensions in meters
7.32= a K constant for dimensions in feet or inches
ε
r
= 1 (air)
ε
r
= 2 (oil)
C
ε
7.32 L
×
Log D d
⁄
(
)
--------------------------pF
=
Cair
ε
air
24 0.95
×
Log 1 0.016
⁄
(
)
----------------------------------- pF
12.7pF
=
=
Cair
ε
air
7.32 0.82
×
Log 1 0.06
⁄
(
)
-------------------------------- pF
12.7pF
=
=
Coil
ε
oil
24 0.95
×
Log 1 0.016
⁄
(
)
----------------------------------- pF
25.4pF
=
=
Coil
ε
oil
7.32 3.12
×
Log 3.28 0.05
⁄
(
)
---------------------------------------- pF
25.4pF
=
=