DH Instruments FPG8601, Operation And Maintenance Manual

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FPG8601™/VLPC™ OPERATION AND MAINTENANCE MANUAL
© 2007 DH Instruments, a Fluke Company Page 142
Table 52.
FPG Defined Pressure Calculation Variables
VARIABLE UNITS DESCRIPTION
A
ˆ
K
2
▪ (Torr ▪ mm)
-2
Reduced constant for transpiration (value for N
2
: 1.20 ▪ 10
6
)
B
ˆ
K ▪ (Torr ▪ mm)
-1
Reduced constant for transpiration (value for N
2
: 1.00 ▪ 10
3
)
C
ˆ
K
0.5
▪ (Torr ▪ mm)
-0.5
Reduced constant for transpiration (value for N
2
: 14.0)
T
K Average gas temperature for transpiration correction
A
(Torr ▪ mm)
-2
Constant for transpiration
A
20
m
2
Effective area of piston-cylinder at 20 °C
A
θ
m
2
Effective area of piston-cylinder at temperature
θ
B (Torr ▪ mm)
-1
Constant for transpiration
C
(Torr ▪ mm)
-0.5
Constant for transpiration
d
m
Smallest internal diameter in DUT – where temperature
transition occurs
g
m/s
2
Local acceleration of gravity
h
D
m
DUT height – distance of DUT above FPG reference level
(negative if below)
K
b
cnt/Pa
Buoyancy coefficient: quantifying the effect of change in
lubrication pressure (
K
b
>0
)
K
cal
N/cnt
Calibration coefficient of load cell (depends on calibration
conditions)
K
d
cnt/Pa
Drag coefficient: quantifying the effect of change in differential
lubrication pressure across piston (
K
d
>0
)
m
cal
kg True mass of internal calibration mass
M
gas
mol
-1
Molar mass of test gas
N cnt
Number of counts output by load cell representing force
measured (1 count = 1 mg under calibration conditions)
N
cal
cnt
Number of counts output by load cell after lowering internal
calibration mass
P
A
Paa Pressure at DUT in absolute mode
P
A,T
Pa Pressure at DUT with transpiration correction
P
AD
Pa Differential pressure at DUT in absolute differential mode
P
AD,T
Pa
Absolute differential pressure at DUT with transpiration
correction
P
G
Pa Pressure at DUT in gauge mode
P
lub
Paa Lubrication pressure
P
ref
Paa
Reference pressure (lower mounting post) measured by
atmospheric pressure sensor in gauge mode and residual
vacuum sensor in absolute mode
P
ref,0
Paa Reference pressure at tare
P
ref,T
Paa Reference pressure with transpiration correction
R
N•m/mol•K Universal gas constant (
= 8314.411
)
T
DUT
K Temperature of DUT (i.e., head temperature)
T
ref
K Temperature of reference pressure gas