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3.
CHARACTERISTICS
3.1
DATA LOGGER CHARACTERISTICS
Measurement frequency:
Programmable from 1s to 99hrs
Clock drift:
1min / month
Memory size:
1Mb with data compression.
PC interface:
Radio transmission
Operating temperature:
-5°C / +35°C
3.2
CHARACTERISTICS OF THE MEASUREMENT
3.2.1
Turbidity channel
Sensor:
Seapoint STM probe
Ranges:
25 NTU, 125 NTU or 750 NTU: choice between manual and automatic range.
Turbidity range (NTU)
Linearity
Resolution (NTU)
0 – 25
< 5%
< 0.007
0 – 125
< 5%
< 0.035
0 – 750
(Non linear from 750 to 2000)
< 5%
(0 to 750 NTU)
< 0.5
(0 to 750 NTU)
Automatic
As per range
3.2.2
Selection of Turbidity measurement range
The measurement range of the Turbidity channel may be forced by the user (choice between the 3 ranges) or
configured in "automatic" mode.
In "automatic" mode, the probe selects the best range to maximize the accuracy of measurement. The algorithm
that allows automatic range selection carries out 1 to 3 measurements to determine the optimum range.
The duration of each measurement, with no range change, is 1s.
The duration of each measurement, with 1 or 2 range changes, is shown in the table below.
Turbidity value to be
measured
Previous turbidity range
0 – 25 NTU
0 – 125 NTU
0 – 750 NTU
MEAS < 22 NTU
1s
2s
2s
22 NTU < MEAS < 110 NTU
2s
1s
2s
MEAS > 750 NTU
3s
2s
1s
Range selection is done by configuring channel 2 according to the table below:
A range change may result in a start of block (
This corresponds to a On/Off
) being created in the
measurement file. This start of block implies a new dating for the measurements. This is achieved when the
programmed measurement frequency is less than the time required for processing. New dating of the
measurements takes place when the programmed frequency is 1 or 2 seconds and there has been a range
change in the measurement cycle.
