| Description: | In the original Campbell CR10 software provided by the vendor (version 1),
the EBBR had incorrect calibration pressure sensor slopes and offsets.
The slopes and offset was carried through into version 2 of the
software and was not discovered by the mentor (me) until sometime later.
The calibration and slope did not deleteriously affect calculations in
the program since only a four percent reduction in atmospheric pressure
measurement resulted (the calculations are not very sensitive to small
errors in pressure). The vendor does not recall how the wrong
calibrations came to be used.
Version 4 of the CR10 program includes the proper calibration and offset.
This remedies the apparent offset problem (it was actually a calibration
and offset problem). In comparisons with the co-located SMOS pressure
sensor, the difference between the SMOS and EBBR pressure values appeared
almost constant with time, hence the assumption of an offset problem.
However, the EBBR pressure sensor offsets are so large (a consequence of
tailoring the calibration curve to a small range of elevations in which the
calibration applies) that the very small error in slope was difficult to
recognize.
The outputted pressure values for the EBBR system can be corrected
with the following information and equations.
Old Slope Old Offset New Slope New Offset
0.01952 81.24 0.02031 81.27
Correct Pressure =
((Current Pressure Data - 81.24)*0.02031/0.01952) + 81.27
= 1.04047*(Current Pressure Data) - 3.258 |