DH Instruments FPG8601, Operation And Maintenance Manual

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FPG8601™/VLPC™ OPERATION AND MAINTENANCE MANUAL
© 2007 DH Instruments, a Fluke Company Page 140
11.3 FPG8601 PRESSURE CALCULATIONS
11.3.1 COMPENSATED PRESSURES
The FPG calculates compensated pressures (seen at the DUT, without thermal transpiration
correction*) following:
( )
D ref hi G FPG G
gh ρ ρ P P
− − =
,
Δ
D hi A FPG AD
gh ρ P P
− =
,
Δ
D hi ref A FPG A
gh ρ P P P
− + =
,
Δ
*Thermal transpiration correction is applied when specified by the user. See Section 11.3.4.
11.3.2 DIFFERENTIAL PRESSURES
Differential pressures ( P
hi
-P
ref
), at the FPG reference level, are defined following:
( )( ) [ ]
20 1
) (
Δ
Δ
20
3 2 1
,
− + + ⋅
+ + + ⋅
= =
θ α α A
N δ N δ N δ N K
A
F
P
C P
cal
θ
G FPG
( )( ) [ ]
20 1
) (
Δ
Δ
20
2 1
, − + + ⋅
+ + ⋅
= =
θ α α A
N δ N δ N K
A
F
P
C P
cal
θ
A FPG
11.3.3 CORRECTION TERMS
Corrections to the balance output based on changes in buoyancy and drag on the piston,
carriage and load cell are calculated following:
( )
0 lub, lub 1
P P K N δ
b
− ⋅ − =
( ) ( )
[ ]
0 , 0 lub, lub 2 ref ref d
P P P P K N δ
− − − ⋅ =
R Z K
M
T
P
T
P
g V N δ
ref cal
gas
ref
ref
ref
ref
ext
⋅ ⋅
⋅
⎥
⎥
⎦
⎤
⎢
⎢
⎣
⎡
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
−
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
⋅ ⋅ =
0 , 0 ,
0 ,
3