Stability of Water Temperature in the conductivity
and temperature calibration system
and Result of calibration experiments
The purpose of this study is to investigate the temperature distribution in the
bath of the conductivity and temperature calibration system (CT bath system) equipped
for Japanese-Argo program in 2000, and to show the results of calibration of sensors
which were actually launched in 2001 in the North Pacific as the Japanese-Argo floats.
On the temperature and conductivity sensor calibration, controlling temperature of
water in the bath during calibration is the most important issue, so the temperature
distribution during calibration was examined. As the results of this experiments,
water temperature was well controlled within 1.7mK.
The calibrations before the deployment of floats were also performed for eight
sensors. The results of JAMSTEC calibration showed that the difference of
temperature calibration from the manufacturer's calibration was within 1mK with the
standard deviation of less than 0.5mK, and that of conductivity calibration from the
manufacturer's was 0.5mS/m (corresponding to 0.0042psu at 24 degree-C) with the
standard deviation of 0.2mS/m (corresponding to 0.0016psu at 24 degree-C).
Keywords : Argo project，Argo profiling float，Calibration bath system，temperature
*1 Department of Marine Science, Marine Works Japan LTD
*2 Frontier Observation System for Global Change
*3 Ocean Observation and Research Department
2. Calibration bath system for profiling float sensor.
Photo 1 Argo float calibration bath (left) and controller(right).
Photo 2 Argo CT (Conductivity and Temperature) sensors（SBE41）
attached to end-cap for connecting to signal cable.
Before calibration, sensors have to be removed from Argo float.
Figure 1 Configuration of Argo calibration bath.
3. Validation of calibration bath system.
3.1. Correction of error among temperature sensors used to measure temperature distribution of the bath.
Figure 2 Time change of temperature measured by four SBE3 sensors
during one-point calibration near room temperature.
The water temperature in the bath gradually increased towards room
however differences among each sensor were almost unchanged during
Table 1 Serial Numbers of all sensors used for measurement of temperature
distribution, and the average and standard deviation of each sensor referred from
S/N2522. The date of calibration by manufacture is also shown.
||差の平均値 (器差) ［mK］
3.2. Method of experiment and location of temperature sensors.
Figure 3 Locations of temperature sensors (SBE3) during the measurement
experiment of temperature distribution in radius direction.
Figure 4 Locations of temperature sensors (SBE3) during the experiment
of temperature distribution measurement in vertical direction.
Figure 5 Temperature distribution relative to reference points.
Upper panel shows temperature distribution in radius direction,
and lower panel does the same except for in vertical direction.
Table 2 The standard deviation of reference sensor at
each calibration point during the experiment of temperature
||T Standard Dev ［mK］
||T Standard Dev <［mK］
4. Calibration results of float sensors by calibration bath system.
4.1. Calibration results of SBE41 sensor.
Figure 6 Average（◆）and standard deviation (error bars) of
temperature differences (residuals) from reference sensor at
Figure 7 Conductivity ratio (correction factor to reference
conductivity sensor) is shown for each calibration date,
calculated as the ratio of measured conductivity to true
conductivity calculated from sampled salinity measured with
Autosal®. The ratio sometimes shows large difference as
indicated with a large circle, in most case, such
values are caused by a contamination during water sampling.
4.2. calibration results of FSI sensor
Figure 8 Location of FSI sensor for the wall effect experiment
of conductivity sensor of "Inductive cell".
The wall effects were measured at 9 points horizontally
(A1 to C3 in the upper panel),
and at 3 levels (middle to bottom in the lower panel).
Figure 9 Results of wall effect experiment for middle layer
and bottom layer.
The horizontal axis shows the distance from sidewall,
and the vertical axis shows the ratio of conductivity reduction.