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Pressurements PressCal
Users Manual
8-2
Pressure Equation
()
()
()
[]
hg
ttA
c
P
f
rc
mi
a
gm
i
e
ΔΡ+
−++Ρ+
+
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
Ρ
Ρ
−⋅Σ
=
ααλ
σ
ρ
11
1
0
1
where
e
P gauge pressure measurements
i
m
i
Σ total mass applied on piston (including all float elements)
g
local gravity
a
P density of air
mi
P density of weights
0
A effective area of piston-cylinder assembly at reference temperature
r
t at null
pressure
λ
pressure distortion coefficient of the piston-cylinder assembly
p
a linear thermal expansion coefficient of the piston
c
a linear thermal expansion coefficient of the cylinder
t temperature of the piston-cylinder assembly
σ
surface tension of the fluid
c
piston circumference
f
P measuring fluid density
hΔ
difference between the reference height level
i
h and the height of the instrument
under calibration
2
h , e.g.
21
hhh −=Δ
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