Sea-Bird Electronics SBE 45 MicroTSG, User Manual

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Section 2: Description of MicroTSG SBE 45
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Remote Temperature Sensor (optional)
The optional 90402 – SBE 45 Power, Navigation, and Remote Temperature
Interface Box can append the output of an optional SBE 38 temperature sensor
to the output from the MicroTSG. Often, the MicroTSG is mounted in the
interior of the vessel. In this configuration the recorded conductivity is correct,
but the water temperature has changed as it has passed through the plumbing
system. The remote temperature sensor can be placed in a location that
provides more accurate measurement of the sea surface water temperature.
The ideal location for the remote sensor is at the seawater intake (before
the pump) near the bow of the ship.
This minimizes contamination of the
surface temperature measurement by the ship’s own thermal mass.
To compute salinity, always use the data from the temperature sensor on
the MicroTSG, not from the remote temperature sensor
. Conductivity has
a strong thermal coefficient; therefore, it is critical to know the temperature of
the water when the conductivity sensor samples it in order to compute salinity
correctly. On a typical installation, there may be 20 to 30 meters of plumbing
between the remote temperature sensor and the MicroTSG. As the water flows
through the pipes it changes temperature dramatically, making the data from
the remote temperature sensor an inaccurate representation of the temperature
when the water reaches the conductivity sensor.
Use the remote temperature
sensor only to report surface temperature, and to calculate density and
sound velocity (density and sound velocity are a function of salinity
and temperature)
.
Notes:
•
See the Interface Box manual for
operation of the MicroTSG with
the Interface Box. The Interface
Box can be added to the system
at any time, and does not
need to be part of the original
MicroTSG order.
•
Sea-Bird software (Seasave real-
time data acquisition and SBE
Data Processing’s Data
Conversion and Derive modules)
uses the data from the
MicroTSG’s temperature and
conductivity sensors to calculate
salinity, and then uses that
salinity with the temperature from
the remote temperature sensor
to calculate density and
sound velocity.
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