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42
From
→
To
↓
psi
"H2O 'H2O mm H20 m H20 "HG mm HG atm
mbar
bar
kPa
MPa
psi
1
.036127 .43275 .0014223 1.4223 .49116 .019337 14.696 .014503 14.5039 .14503
145.03
"H2O
27.730
1
12
.039372
39.372 13.596 .53525 406.78 .40147
401.47
4.0147
4016.1
'H2O
2.3108
.08333
1
.003281
3.281
1.133 .044604 33.8983 .033456 33.4558
.3346
334.6
mm H20
704.32
25.399 304.788
1
1000
345.32 13.595 10332 10.197
10197
101.97 101970
m H20
.70432 .025399 .304788
.001
1
.34532 .013595 10.332 .010197 10.197
.10197
101.97
"HG
2.036
.073552 .882624 .0028959 2.8959
1
.03937 29.920 .029529 29.529
.2953
295.3
mm HG
51.706
1.8683 22.4196 .073558
73.558
25.4
1
760
.75008
750.08
7.5008
7500.8
atm
.06805 .0024583 .0294996 .0000968
.0968
.03342 .0013158
1
.0009869 .98692 .009869
9.869
mbar
68.947
2.4908 29.8896 .098068
98.068 33.863 1.3332 1013.2
1
1000
10
10000
bar
.068947 .0024908 .0298896 .0000981 .098068 .033863 .001333 1.0132
.001
1
.01
10
kPa
6.8947
.24908 2.98896 .0098068 9.8068 3.3863 .13332 101.320
.1
100
1
1000
MPa
.006895 .000249 .002988 .00000981 .009807 .003386 .000133 .101320 .0001
.1
.001
1
Table 3 - Engineering Units Multiplication Factors
Note
: Due to changes in specific gravity with temperature, the factors for mercury and water in
Table 3 are approximations.
D.2 Temperature Correction
Careful selection of materials is made in constructing the vibrating wire piezometer to minimize
thermal effects; however, most units still have a slight temperature coefficient. Consult the
supplied calibration report to obtain the coefficient for a given piezometer.
Since piezometers are normally installed in a tranquil and constant temperature environment,
corrections are not normally required. If however, that is not the case for a selected installation,
corrections can be made using the internal thermistor for temperature measurement.
Temperature correction equation is as follows:
Temperature Correction
=
(Current Temperature - Initial Zero Temperature)
×
Thermal Factor
Or
P
T
= (T
1
-T
0
) x K
Equation 11 - Temperature Correction
The calculated correction would then be
added
to the Pressure calculated using Equation 10. (If
the engineering units were converted, remember to apply the same conversion to the calculated
temperature correction!) For example, assume the initial temperature was 22
°
C, the current
temperature is 15
°
C, and the thermal coefficient is
−
.01879 PSI per
°
C rise. The temperature
correction is 0.13 PSI. Adding this to the calculated pressure in the beginning of this appendix
results in a temperature corrected pressure of 19.98 PSI.