18
6. DATA REDUCTION
6.1 Pressure Calculation
The pressure measured by the piezometer is determined by the following linear equation:
Pressure
=
(Current Reading - Initial Reading)
×
Gage Factor
Or
P = (R
1
– R
0
)
×
G
Equation 1 - Convert Digits to Pressure
Where;
P is the applied pressure in kPa or psi.
R
0
is the initial output in millivolts, volts, or milliamps.
R
1
is the current output in millivolts, volts, or milliamps.
G is the gage factor, as shown on the supplied calibration report.
For Example;
Model 3400-1-100KPA Input Voltage = 12.0 volts
R
0
= -0.0.006 mV
R
1
= 18.0 mV
G = 1.004 kPa/mV
P = 1.004 (18.0 – (– 0.006)) x 10/12= 15 kPa
The Initial Reading (R
0
) is normally obtained at the time of installation, as described in Section
4.1. To convert the output to other engineering units, multiply the Calibration Factor by the
conversion multiplier listed in Table 2.
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 .002458 .029499 .0000968 .0968 .03342 .001315
1
.000986 .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 .002490 .029889 .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 .0000098 .009807 .003386 .000133 .101320 .0001
.1
.001
1
Table 2 - Engineering Units Multiplication Factors
