16
Analog Sampling Best
Practices
Analog
outputs
of
0.25V
and
lower
correspond
to
concentrations that are too low for the ABS to measure, and
should be considered invalid. These readings may result from
an object in the measurement volume, or the transducer not
being fully submerged.
In order to obtain the most accurate results it is recommended
that the LISST-ABS be powered up and allowed to sample in
the automatic mode (green LED double blinking) for 30 seconds
or more before recording the analog voltage output. This 30
second wait should be done every time power is applied.
During these 30 seconds the LISST-ABS is obtaining a running
average of attenuation that is used internally to compute the
concentration value. Shorter waits will result in noisier
measurements.
It is also recommended that bursts of 30 measurements or
more be recorded and averaged to obtain the best results.
Because of the LISST-ABS measures concentration within a
small volume, natural variability in the distribution of particles
will be reflected in the ABS measurements
For example if measurements every 15 minutes are desired we
recommend the following procedure:
1) Power up the LISST-ABS 45 seconds before the beginning of
the desired sample time and allow it to sample.
2) Record 60 measurements of the analog voltage 1 second
apart.
3) Power down the LISST-ABS and wait till the next sample time.
For suggestions on mounting, cleaning and maintenance
please see Section 2.6.
Содержание LISST-ABS
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