Geokon 4580, Instruction Manual

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11
4.2 Temperature Correction
Careful selection of materials is made in constructing the vibrating wire pressure transducer to
minimize thermal effects, however, most units still have a slight temperature coefficient. Consult
the supplied calibration report (see Appendix D for a sample calibration report) to obtain the
coefficient for a given sensor.
Since piezometers are normally installed in a tranquil temperature environment, corrections are
not normally required. If that is not the case for a selected installation, corrections can be made
using the internal thermistor for temperature measurement. See Section 3.4 for instructions
regarding obtaining the sensor temperature.
The temperature correction equation is as follows:
P
temperature
= (T
1
-T
0
)
×
K
×
F
1
Equation 3 - Temperature Correction
Where;
T
1
represents the current temperature.
T
0
represents the initial temperature.
K is the thermal coefficient from the supplied calibration report.
F
1
is an optional multiplier to convert to engineering units (see Table 1).
The calculated correction would then be added to the Pressure calculated using Equation 2. If
the engineering units were converted remember to apply the same conversion to the calculated
temperature correction!
4.3 Barometric Correction
Since the unvented pressure transducer is hermetically sealed, it responds not only to water
pressure changes but also to changes in atmospheric pressure. That being the case, corrections
may be necessary. For example, ignoring a barometric pressure change from 29 to 31 inches of
mercury would result in ≈ 1 psi of error (or ≈ 2.3 feet if monitoring water level in a well).
The barometric correction equation is as follows:
P
barometric
= (S
1
-S
0
)
×
F
2
Equation 4 - Barometric Correction
Where;
S
1
represents the current barometric pressure.
S
0
represents the initial barometric pressure.
F
2
is a multiplier to convert the barometric pressure units (see Table 1) to the required units.