User manual

Table Of Contents
Chapter 5
Operations
Ballasting the MMP
Ballast sheet calculations must be performed for each new deployment. Accurate
ballasting is absolutely essential, as the lift capacity of the MMP is limited by the strength of the
coupling between the drive wheel and the mooring cable. Ballasting errors of a few pounds will
trap the profiler against one of the stops for the duration of the deployment. Data will be returned
by the system, but it will all be from a single depth. Accurate ballasting requires:
Precise measurements of the MMP air weight and MMP weight in water of some
known density.
Knowledge of the effective compressibility of the profiler and the dependence of
profiler density on temperature.
With these numbers available, the required weight of lead ballast can be calculated for a
particular deployment if the density, pressure, and temperature of the water at the neutral point of
the planned profile are known. It is the in situ
quantities that are required, not the potential
density or temperature.
A completed ballast sheet with computed ballast values is included in hard copy form
with the MMP documentation and in electronic form on a floppy disk. McLane calculates and
attaches an appropriate quantity of lead ballast for the initial deployment based on this ballast
sheet. The ballast calculation is based on in situ density and deployment defined pressure
information that you supply to McLane. In addition, the CD that contains MMP Documentation
includes blank ballast sheets.
IMPORTANT
Any weight change must be considered in the MMP ballast calculation. Changes that affect
ballast include adding autonomous sensors, replacing glass spheres, changing the main battery
pack or swapping existing sensors. If your deployment parameters change, contact McLane for
assistance with ballast re-calculation.
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