11. APPENDIX
Page 143
© 2007 DH Instruments, a Fluke Company
VARIABLE
UNITS
DESCRIPTION
T
ref,0
K
Temperature of reference pressure gas at tare
V
ext
m
3
Total external volume of piston
X
hi
Torr
▪
mm
Pressure geometry factor for transpiration – P
hi
X
ref
Torr
▪
mm
Pressure geometry factor for transpiration - P
ref
Z
ref,0
-
Compressibility of reference pressure gas at tare
Δ
F
N
Net change in force (from tare) on piston
Δ
P
FPG,A
Pa
Differential pressure between high and reference test ports at
FPG reference level in absolute mode
Δ
P
FPG,G
Pa
Differential pressure between high and reference test ports at
FPG reference level in gauge mode
α
C
°C
-1
Linear thermal expansion coefficient of cylinder
α
P
°C
-1
Linear thermal expansion coefficient of piston
δ
N
1
cnt
Correction to N resulting from change in buoyancy of piston,
load cell and linkage due to change in lubrication pressure
δ
N
2
cnt
Correction to N resulting from change in drag force on piston
due to change in difference between lubrication pressure and
test pressures
δ
N
3
cnt
Correction to N resulting from change in buoyancy of piston due
to change in reference pressure
θ
°C
Temperature of piston-cylinder
ρ
hi
kg/m
3
Density of high pressure test gas (upper mounting post)
ρ
lub
kg/m
3
Density of lubrication gas
ρ
m
kg/m
3
Density of internal mass
ρ
ref
kg/m
3
Density of reference pressure test gas (lower mounting post)
