Wet Labs ac-s, User Manual

Page: 17 / 43

ac-s User’s Guide (ac-s) Revision F 9 Feb. 2006 9
•
Once every couple of days, take a data file in air to track any instrument drift. The
instrument must be very clean and completely dry to achieve an accurate air
calibration measurement. Using compressed dry nitrogen or oil-free dry air to blow
the instrument’s flow tubes and windows dry will speed the drying process.
•
Upon deployment, the instrument should be lowered to just below the water’s surface.
Turn on the instrument and pump and check to ensure that the pump has primed and
is operating properly. Lower the package to a depth of 10–20 meters. Run the
instrument for 3–5 minutes to allow the motor controller to stabilize, the flow tubes to
clear and the instrument to begin to equilibrate with the water temperature.
•
After the warm up period, raise the package to just below the surface and begin data
collection. The initial depth will be dependent on the natural surface conditions and
the amount of bubbles that the ship itself is generating. Steadily lower the cage
through the water column.
•
The upcast can proceed immediately after the downcast. It is your choice whether to
open a new data file for the upcast or include the down and upcast data in a single file.
•
Once the cage is back to the just below the surface, stop the data collection and turn
off the pump. Carefully bring the cage on deck and lash it down. Give the cage and
instrument a fresh water wash down after every cast. If this is not practical, wash the
instrument at the end of each data collection day. Holding a hose (at low pressure)
over the pump discharge port will flush the tubing and the flow tubes. Rinse the
flanges and connectors. If leaving the instrument on deck for more than a few
minutes, cover the cage with a tarp to avoid over-heating the instrument due to solar
insolation. At the end of each data collection day, remove the tubes and carefully
clean and dry both the flow tubes and windows. Failure to flush the instrument with
fresh water may cause corrosion damage over time.
2.3 Data Collection
WET Labs offers several output configuration options to provide flexible interfacing to
different systems. These various output protocols are discussed at length in the Data
Processing Section of the manual. Unless supplied with a custom output protocol the
instrument powers up in a free run mode. This means that when turned on the unit
automatically begins acquiring data and outputting that data in its appropriate format.
Typically the instrument comes supplied with RS-485 and RS-232 output operating at
115,200 baud.
RS-485:
For longer cable lengths and maximum data integrity, RS-485 protocol is the
preferred method of data transfer. Data is transmitted from the instrument in a binary
format. To view this data, you must have a program capable of reading binary data. If
you are using our WETView software package, the binary read is done automatically. If