Sea-Bird Electronics SBE 45 MicroTSG, Руководство пользователя

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4
Temperature Sensors
The temperature sensor
slope and offset entries in the configuration (.con or .xmlcon) file in SEASOFT permit the user
to make corrections for sensor drift between calibrations. The correction formula is:
corrected temperature = slope * (computed temperature) + offset
where :
slope = (true temperature span) / (instrument reading temperature span)
offset = (true temperature - instrument reading temperature) * slope
measured at 0.0 ° C
For newly calibrated sensors, use slope = 1.0, offset = 0.0.
Sea-Bird temperature sensors usually drift by changing offset (an error of equal magnitude at all temperatures). In
general, the drift can be toward higher or lower temperature with time; however, for a specific sensor the drift remains
the same sign (direction) for many consecutive years. Many years of experience with thousands of sensors indicates
that the drift is smooth and uniform with time, allowing users to make very accurate drift corrections to field data based
only on pre- and post-cruise laboratory calibrations.
Span errors cause slope errors, as described in the equation for slope above. Sea-Bird temperature sensors rarely exhibit
span errors larger than 0.005 °C over the range -5 to 35 °C, even after years of drift. Temperature calibrations
performed at Sea-Bird since January 1995 have slope errors less than 0.0002 °C in 30 °C. Prior to January 1995, some
calibrations were delivered that include slope errors up to 0.004 °C in 30 °C because of undetected systematic errors in
calibration. A slope error that increases by more than ±0.0002 [°C per °C per year] indicates an unusual aging of
electronic components and is symptomatic of sensor malfunction.
Therefore, Sea-Bird recommends that drift
corrections
to temperature sensors be made assuming no slope error, unless there is strong evidence to the contrary or a
special need.
Calibration checks at-sea are advisable for consistency checks of the sensor drift rate and for early detection of sensor
malfunction. However, data from reversing thermometers is rarely accurate enough to make calibration corrections that
are better than those possible by shore-based laboratory calibrations.
For the SBE 9 plus , a proven alternate consistency
check is to use dual SBE 3 temperature sensors on the CTD and to track the difference in drift rates between the two
sensors. In the deep ocean, where temperatures are uniform, the difference in temperature measured by two sensors can
be resolved to better than 0.0002 °C and will change smoothly with time as predicted by the difference in drift rates of
the two sensors.
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