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11 Reference
11
Equivalent Internal Volume
1) Equation for calculating equivalent internal volume
Equivalent internal volume can be calculated with the following equation:
Where:
Ve:
Equivalent internal volume [mL]
Vw:
Internal volume of the tested part and the tubing [mL]
Vm:
Internal volume of the MASTER and the tubing [mL]
Vt:
Tester internal volume [mL] (= 11 mL) (Standard pneumatic circuit)
Ks:
Change in internal volume of the sensor per unit pressure change [mL/kPa] (= 0.005 mL/kPa)
Kw:
Change in internal volume of the tested part per unit pressure change [mL/kPa]
P:
Test pressure [kPa]
2) Equivalent internal volume when the internal volume of the MASTER is almost equal to that of the
WORK (Tested part) (Vw = Vm)
(In other words, the MASTER-side circuit is same in volume as the WORK-side, and both are rigid
enough that the test pressure does not physically change their dimensions.)
If the internal volume of the tested part remains unchanged (Kw = 0) during detection even though
charged with pressure,
Equation A
can be simplified to
Equation B
:
Ks(1 + Vw/Vm) + Kw = 2Ks = 0.01 [mL/kPa]
Ve = Vw + Vt + 0.01 × (101.3 + P)
3) Equivalent internal volume when a MASTER Chamber (
i.g.
MC-F02A, whose internal volume is 109
mL) is used as a MASTER
If the internal volume of the tested part remains unchanged (Kw = 0) during detection even though
charged with pressure,
Equation
A
can be simplified to
Equation
C
:
Ve = Vw + Vt + 0.005 × (1+ Vw/109) × (101.3 + P)
Calculation of Leak Rate
The relationship between differential pressure and leak rate per unit time is given by the following equation:
The LS-R700 uses the above equation to calculate the leak rate. Note that the tester uses standard
atmospheric pressure for this calculation.
Tester internal volume, Vt, of each pneumatic circuit (including CAL port)
Intelligent 1 pneumatic circuit, A1: 11 mL
Intelligent 2 pneumatic circuit, A2: 13 mL
A1 pneumatic circuit for small volume, AS1: 11mL
Small volume pneumatic circuit, A01, with stop valves: 6 mL
Secondary pressure detection method C: 7 mL
Where:
Q: Volumetric leak rate [mL/min]
P:
Pressure drop due to leaks [Pa]
Ve: Equivalent internal volume [mL]
T:
Detection time(s)
(
) (
)
(
)
{
} (
)
P
+
3
.
101
×
Kw
+
Vt
+
Vm
/
Vt
+
Vw
+
1
×
Ks
+
Vt
+
Vw
=
Ve
T
60
10
013
.
1
P
Ve
Q
5
×
×
∆
×
=
A
B
C
When the volume of the Master is
smaller than that of the tested
part, Ve becomes larger, which
causes lowering the DPS
sensitivity
NOTE
