E10160-200722
FOP
Page 9
T
1
= 80°F
B
o
= 29.8 in. Hg
B
1
= 29.4 in. Hg
P
corr
= 22.25 - 0.01879 (80 - 65) - 0.491 (29.4 - 29.8)
P
corr
= 22.25 - 0.282 + 0.196 = 22.16 psi
SI units (bar)
P
corr
= P
rec
- CT (T
1
– T
0
) - (B
1
- B
0
)
where:
P
corr
= corrected pressure in bar
P
rec
= recorded pressure in bar
CT
= temperature correction factor in bar/
o
C
T
o
T
1
= Initial (at installation) and current temperature readings (
o
C)
B
o
B
1
= Initial (at installation) and current barometric pressure in bar.
Example:
P
rec
= 4.500 bar
CT
= 0.00143 bar/°C
T
o
= 20°C
T
1
= 25°C
B
o
= 1.013 bar
B
1
= 1.002 bar
P
corr
= 4.500 - 0.00143 (25 - 20)
– (1.002 – 1.013)
P
corr
= 4.500 - 0.007 + 0.011 = 4.504 bar
2.6 POLYNOMIAL PRESSURE EQUATIONS for FOP-MicroPZ and FOP-PZ
Piezometers
For piezometers FOP-MicroPZ and FOP-PZ with polynomial equation you should assign
the gauge factor 0001000 for all gauges. The calibration factors are obtained using a
polynomial regression of 3
rd
degree. Then to convert changes in readings (internal unit in
nm) to changes in pressure use the following equation:
P
rec
= c3 (L-Lc)
3
+ c2 (L-Lc)
2
+ c1 (L-Lc) + c0
where:
P
rec
=
Pressure in bar, kPa or psi
c0,c1,c2,c3:
=
Calibration factors (see on calibration data sheets)
L
=
Current reading in nm using gauge factor 0001000 inside the
readout unit
Lc (center)
=
Mean reading in nm (see value identified center on the
calibration data sheet.