LISST-Tau
User’s Manual
Operation Details
Page 14
5.
Clean-water Baseline Measurement (Calibration)
The LISST-Tau baseline is measured using very clean water at the factory and may not
need to be measured in the field. However, periodic baseline measurements assure the
highest measurement accuracy, and correct for factors such as scratched windows or rough
handling that can affect the performance of the instrument. The procedure shown below
provides the necessary steps needed to measure a new baseline. Note: Accurate results
require careful work and water free of any particles or dissolved substances, such as
deionized water.
STEP
ACTION
RESULT
1
•
The instrument will need to be submerged in the water
used for its baseline, so start by cleaning the entire
exterior of the LISST-Tau.
•
Clean the windows as discussed in
on page 13. Clean windows are essential for an
accurate baseline measurement.
Windows and
instrument very clean
2
•
Fill a clean container with highly filtered, degassed
water. The container must be large enough to fully
submerged the LISST-Tau. It is recommended that the
water be continuously recirculated through a 0.2-
micron filter while monitoring the beam attenuation.
•
Monitor the attenuation as the water is filtered and the
temperature is equilibrating. Decreasing attenuation
means the results are improving.
•
For best results, clean the windows repeatedly until the
attenuation is the same after each cleaning.
Flow Through
Chamber installed or
clean water container
prepared.
3
•
Once a stable value has been obtained press the
Recalibrate button on the LISST-Tau software.
•
Averaged values will be obtained and displayed on the
screen. Press Yes to accept the current values and
reset the baseline. Press Cancel to stop the procedure
and not make any changes.
•
WARNING: Once re-calibrated the instrument cannot
be returned to the previous calibration.
•
See Section 3 for more details on using the LISST-Tau
software.
Values are stable and
re-calibration can
begin
4
•
The instrument has been recalibrated and the values
being display will be using the new baseline.
Instrument has been
re-calibrated
