PG7000™ OPERATION AND MAINTENANCE MANUAL
© 1998-2008 DH Instruments, a Fluke Company
Page 206
Table 31.
PG7000 Defined Pressure Calculation Variables
VARIABLE
DEFINITION
UNITS
SOURCE OF VALUE
/
π
Α
P
θ
,
Piston radius at temperature
θ
and
pressure P
m Calculated.
A
20,0
Piston effective area at 20°C,
P
atm
mm
2
Piston-cylinder module file (3.11.1.3).
A
θ
,P
Piston effective area at temperature
θ
,
pressure P
m
2
Calculated from
A
20,0
in piston-cylinder
module file (3.11.1.3).
G Local
gravity
m/s
2
Local, standard or user as specified in
current SETUP file (3.10).
K
N
Nominal mass to pressure conversion
coefficient for a given piston-cylinder size
Pa/kg
Calculated from
A
20,0
and standard
conditions.
M
Mass load
kg
Current mass loading instruction (3.6,
3.9.11).
P
A
Absolute pressure
Paa
Calculated.
P
atm
Atmospheric (ambient) pressure
Paa
Internal measurement, user entered value
or standard as specified by SETUP file
(3.10).
P
G
Gauge
pressure
Pa
Calculated.
P
HA
Fluid head correction in absolute mode
Pa
Calculated using device heights and
medium (7.2.3.2, 3.9.7, 3.11.3).
P
HG
Fluid head correction in gauge mode
Pa
Calculated using device heights and
medium (7.2.3.2, 3.9.7, 3.11.3).
P
HD
Fluid head correction in high line
differential mode
Pa
Calculated using device heights and
medium (7.2.3.2, 3.9.7, 3.11.3).
P
L
Line Pressure
Pa
High line differential mode only (3.9.4.2).
P
nom
Nominal
pressure
Pa
In pressure to mass mode
P
nom
=P
req
In mass to pressure mode
P
nom
=M·K
N
P
offset
Difference between PG7601 and RPM at
the static pressure of differential mode
Pa
Determined experimentally in PG7601
differential mode operation (see Section
3.9.4.1, Selecting Differential Mode, Setting
Static Pressure, Finding RPM Offset).
P
RPM
Current static pressure reading from
reference pressure monitor
Paa
Read automatically from external atm P
source specified by SETUP file. Used in
PG7601 differential mode only (3.10, 3.9.4.1).
Δ
P
D
Differential pressure
Pa
Calculated. PG7601 differential mode only
(3.9.4.1).
Δ
P
HLD
High line differential pressure
Pa
Calculated. High line differential mode only
(3.9.4.2).
Δ
P
nom
Nominal differential pressure in high line
differential mode
Pa
In pressure to mass mode
Δ
P
nom
=
Δ
P
req
In mass to pressure mode
Δ
P
nom
=(M
R
- M
RX
)·K
N
.
Γ
Surface tension coefficient
N/m
Piston-cylinder module file (3.11.1.3).
α
C
Cylinder linear thermal expansion coefficient
°C
-1
Piston-cylinder module file (3.11.1.3).
α
P
Piston linear thermal expansion coefficient
°C
-1
Piston-cylinder module file (3.11.1.3).
λ
Piston-cylinder pressure coefficient
Pa
-1
Piston-cylinder module file (3.11.1.3).
θ
Temperature of piston-cylinder
°C
Internal measurement, user entered value
or standard as specified by SETUP file
(3.10).
ρ
a
Air density
kg/m
3
Calculated from standard air density
corrected for actual atmospheric pressure,
ambient temperature and relative humidity
(atm p, humidity and temp source are
specified by SETUP file) (3.10).
ρ
m
Mass density
kg/m
3
Mass set file (3.11.1.8).
Subscripts specific to high line differential mode (see Section 3.9.4.2).
( )
P+
Δ
P
Line pr differential pressure
(reference piston-cylinder)
-
( )
R
Reference
-
( )
RX
Reference, at time of cross float
-
( )
T
Tare
-
( )
TX
Tare, at time of cross float
-
