TURTLE
TOUGH
®
10
Operation
Temperature Measurement
Set the functional switch to °C. The liquid-crystal display will immediately indicate the temperature value. If the
value shown is not stable, the temperature stabilisation time has probably been too short; it will be necessary to
wait until the display has become steady.
Note:
Since most of the M6S sensor is made of plastic material, the sensor should never be used in water samples with
temperatures above 60°C. This would damage the sensor body, the right to claim under warranty would be lost.
Temperature Stabilisation Time
Before carrying out measurements, the sensor must be given sufficient time to adapt to the ambient temperature.
This temperature stabilisation is necessary because a change of temperature affects both the conductivity of the
electrolyte inside the sensor body and the diffusion capacity of the cathode membrane.
The temperature stabilisation time can be calculated in minutes by allowing a waiting time of three-quarters of a
minute for each degree Celsius temperature difference. This results in the following general formula:
Temperature stabilisation time [min] = 3/4 x (maximum °C value-minimum °C value)
For example, in the case of a temperature difference of 40 °C, which is quite likely with field instruments during
summer, the temperature stabilisation time will amount to about 30 minutes.
With sensors that are constantly kept in the measuring liquid, it will not be necessary to observe a temperature
stabilisation time. The best procedure is to wait until the temperature value on the liquid-crystal display remains
stable.
Dissolved Oxygen Measurement
In order to obtain reliable measurements, the Turtle Tough sensor must be placed in a position where the natural
approach flow amounts to a minimum of 30 cm/s.
If there is no natural approach flow, it will be necessary to create an artificial flow. This can be done as follows:
•
The first possibility to create an artificial flow is also the simplest: make a stirring movement with the sensor
by hand.
•
However, where longer distances are involved, especially when measuring at great depth, the hand-generated
approach flow will no longer be adequate since the movement is impeded by the resistance of the liquid.
•
Pull and release the cable continuously during measurement so that the sensor is constantly moving up and
down. Note that this method is not suitable for exact measurement results.
•
Where high-accuracy measurements are required, an absolutely even and reproducible approach flow has
to be created artificially.
•
This can only be done with the aid of a flow transmitter, such as our unique and internationally utility-patented
TT-O₂-FLOW, a device using an oscillating paddle for creating the necessary approach flow.
•
Once the proper approach flow has been established, you can proceed with the measurement of the oxygen
content. Set the functional switch on O₂. The liquid-crystal display will now indicate the value of the oxygen
dissolved in the liquid.
