Geokon 4580, Instruction Manual

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10
The calibration report gives the pressure in certain engineering units. These can be converted to
other engineering units using the multiplication factors shown in Table 1.
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 1 - Engineering Units Multiplication Factors
(Note: Due to changes in specific gravity with temperature, the factors for mercury and water in
the above table are approximate.)
In the special case where the Model 4580 is being used as a Barometer it is necessary to add the
atmospheric pressure at the time of the initial reading. This pressure would best be obtained
locally as an absolute value not corrected for height above sea level. If a local measurement
cannot be obtained then it is permissible to use the barometric pressure recorded on the
calibration report, see Appendix D.
For example:
Suppose the Linear gauge factor is 0.004586 kPa/digit, and the initial reading is 4908 at a
barometric pressure of 990.3 mbar which, converted to kPa equals 99.03 kPa. A subsequent
reading of the barometer equals 5024.
The new barometric pressure = 99.03 + (5024 - 4908) x (0.004586) = 99.56 kPa or 995.6 mbar.
However, where the barometer is being used as a means of correcting for barometric pressure
changes on nearby unvented vibrating wire piezometers then only the change of barometric
pressure is required which in the above case is + 0.53 kPa. This value must be subtracted to
correct for the barometric pressure change
Correction for Barometric pressure changes on unvented piezometers and pressure transducers is
explained in Section 4.3.