Section 6: Routine Maintenance and Calibration
SBE 45
40
Sensor Calibration
Sea-Bird sensors are calibrated by subjecting them to known physical
conditions and measuring the sensor responses. Coefficients are then
computed which may be used with appropriate algorithms to obtain
engineering units. The conductivity and temperature sensors on the MicroTSG
are supplied fully calibrated, with coefficients printed on their respective
Calibration Certificates (see back of manual). These coefficients have been
stored in the MicroTSG’s EEPROM.
We recommend that MicroTSGs be returned to Sea-Bird for calibration.
Conductivity Sensor Calibration
The conductivity sensor incorporates a fixed precision resistor in parallel with
the cell. When the cell is dry and in air, the sensor’s electrical circuitry outputs
a frequency representative of the fixed resistor. This frequency is recorded on
the Calibration Certificate and should remain stable (within 1 Hz) over time.
The primary mechanism for calibration drift in conductivity sensors is the
fouling of the cell by chemical or biological deposits. Fouling changes the cell
geometry, resulting in a shift in cell constant.
Accordingly, the most important determinant of long-term sensor accuracy is
the cleanliness of the cell. We recommend that the conductivity sensors be
calibrated before and after deployment, but particularly when the cell has been
exposed to contamination by oil slicks or biological material.
Temperature Sensor Calibration
The primary source of temperature sensor calibration drift is the aging of the
thermistor element. Sensor drift will usually be a few thousandths of a degree
during the first year, and less in subsequent intervals. Sensor drift is not
substantially dependent upon the environmental conditions of use, and —
unlike platinum or copper elements — the thermistor is insensitive to shock.
Note:
Do not disassemble the MicroTSG
to send the sensors to Sea-Bird for
recalibration
. Package the entire
MicroTSG for shipment, after
removing the AF24173 Anti-Foulant
Device (see
Replacing Anti-Foulant
Device
). Store the AF24173 Anti-
Foulant Device for future use.
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Содержание SBE 45 MicroTSG
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