Appendix G. Barometric Correction (Non-Vented Transducers Only) - Geokon 8020-59 Instruction Manual

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APPENDIX G. BAROMETRIC CORRECTION (NON-VENTED
TRANSDUCERS ONLY)
Since the standard piezometer is hermetically sealed and unvented, it responds to changes in
atmospheric pressure. That being the case, corrections may be necessary, particularly for the
sensitive, low-pressure models.
The digits for the range of the transducer, as shown on the calibration report, may vary
considerably with changes in elevation (offset). It is a simple matter to compensate for this offset
with the 8020-59.
Referring to the example calibration report (Appendix E, Figure 36), note that the average zero
reading (0 psi) is 9139 digits (8020-59 maximum digits) and the average maximum reading (100
psi) is 5691 digits (8020-59 minimum digits). These readings were recorded at an atmospheric
pressure of 1001.4 mbar, corresponding to the conditions and altitude at the Geokon factory. To
compensate for elevation change, take a new zero reading at the site location. This new zero
reading becomes the maximum digits entered into the 8020-59. Add the difference between the
new zero reading and the original zero reading to the maximum reading shown on the calibration
report. This becomes the new minimum digits entered into the 8020-59.
For example:
Calibration Report:
Site Location:
0 psi Average Reading
9139
9950 (+811 digits) 6502
(new maximum digits)
100 psi Average Reading
5691
(new minimum digits)