1.15.3 The temperature sensor
The temperature sensor consists of a platinum resistance
thermometer (type Pt 100 ohms at 0°C), fitted on a thin stainless-steel
housing, able to withstand up to 700 bar. The sensor has a very low
response time (50 ms) and a high stability of reading with ageing.
The drift of reading (sensor plus associated electronics) is less than
0.0003 °C per year.
Type: Pt100@0°C
Measurement range: -3..+50 °C
Accuracy: 0.003 °C
Resolution: 0.0002 °C
Response time: 50 ms @1 m/s
Maximum pressure: 700 bar
Sensor body: AISI 316L
Life: unlimited
Calibration frequency: yearly
Compensation: none.
Maintenance: none.
1.15.4 The conductivity sensor equipped with the "IDRONAUT seven-ring cell"
The conductivity sensor is a unique flow-through self-flushed cell with seven platinum ring electrodes.
The central ring is excited with alternate current flowing to both the outermost rings. The two adjacent
pairs of rings sense the relative drop in voltage due to the electrical conductivity of the measured water.
The outermost pair of rings is grounded to shield the measuring cell from any outside electrical
interference. The cell is mounted in a special cylindrical plastic body, which guarantees thermic
insulation and is filled with silicone oil and provided with a rubber bellow to achieve pressure
compensation.
The IDRONAUT conductivity sensor and its associated electronics
are designed to work both with plain and black platinised platinum
electrodes These electrodes have the advantage that, they can be used
in both clean and dirty water without the fear of contamination.
Should electrode contamination occur, they can be easily cleaned
(even with up to 30% hydrochloric acid) without affecting the CTD
performance or requiring re-calibration. Because of its big internal
diameter and short length, the cell does not need a pump, as it is
easily flushed during profiles.
The other conductivity flow cell sensors available on the market do
not have the technology of the “IDRONAUT seven-ring cell”.
The small, closely spaced temperature and conductivity free-flow
sensors eliminate the need for adding pumping. Time constant of the
conductivity sensor is 50 ms, at 1 meter per second water flow.
Measurement cell: 7 platinum rings deposited inside
a quartz tube. Internal diameter
8mm, length 45mm.
Measurement range: 0..70 mS/cm
Accuracy: 0.003 mS/cm
Resolution: 0.0003 mS/cm
Response time: 50 ms @1 m/s
Max pressure: 700 bar
Sensor body: black plastic and titanium
Compensation: automatic compensation of the pressure and thermal effect on the
cell geometry are performed by the acquisition software.
Life: unlimited.
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