Deep SUNA Manual
For SUNA running firmware version 2.4 or later
5. Configuration Parameters in Context
Concentrations-to-Fit configuration parameter from 3 to 1. Reducing the number of
concentrations to fit improves the precision of the processed data.
Under normal conditions, no other processing parameters need to be changed.
Configuration: Concentrations to Fit, Fit Wavelength Low, Fit Wavelength High
5.4.2 Special Case: Temperature-Salinity Correction
In oceanographic applications, data quality can be improved if temperature and salinity
of the sample are known. Known absorption characteristics of seawater, combined with
the temperature and salinity of the sample permits accurate calculation of the
absorbance due to seawater. This known absorbance is removed from the measured
absorbance, and the remaining absorbance is decomposed for nitrate.
Temperature-Salinity Correction is only available with APF mode. In order to utilize it,
the Fit-for-Salinity configuration parameter has to be Off, and the Temperature-
Correction configuration parameter has to be On. The current salinity ans temperature
values are passed to the sensor running in APF mode via the CTD command. If no
salinity and temperature values are provided, the sensor will skip temperature-salinity
correction and output concentrations based on regular processing.
Configuration: Temperature Correction, Salinity Fitting
5.4.3 Special Case: Bromide Tracing
In freshwater, bromide can be used as a tracer. If the sensor's Bromide Trace
configuration parameter is set to On, the sensor will analyze the measured spectrum for
the presence of bromide, and output the result in its regular frame.
Configuration: Bromide Tracing
5.4.4 Special Case: Highly Absorbing Water
Highly absorbing waters pose a challenge to the sensor. In its normal configuration, the
part of the spectrum with an absorbance of more than 1.3 is excluded from processing.
Using parts of the spectrum of higher absorbance will reduce accuracy and precision of
the measured concentrations. The user may increase the Absorbance Cutoff to a higher
value, to extend the operational range of the sensor at the expense of reduced data
quality.
If the absorbance reaches values between 2.0 and 2.5, data quality deteriorates further.
If the Integration Time Adjustment configuration parameter is set to
On
or
Persistent
,
the sensor will start making measurement using a spectrometer integration time that is
20 times as long as the normal integration time. This longer integration time increases
the signal-to-noise ratio in faint light conditions, and allows the sensor to operate in
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