YSI Professional Plus - Manual (Page 18)

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Auto Stable and Hold All Readings enabled,
then the display will hold the readings once Do
and pH have both reached their Auto Stable
settings. You must press the Esc key to “release”
the held display in order to take subsequent
readings Hold All Readings must be reactivated
after each use!
SALINItY CoRRECtIoN
the last feature in the Sensor menu is the Salinity
correction value which is used to calculate the
dissolved oxygen mg/L and ammonia readings
when a conductivity sensor is not in use. Press
Sensor
, highlight Salinity, and press enter.
then, use the numeric entry screen to enter the
Salinity value of the water you will be testing
from 0 to 70 ppt.
If using a cable with a conductivity sensor, the salinity
measured by the conductivity sensor will be used in the Do and
ammonia mg/L calculations and ‘As Measured’ will be displayed next to Salinity
in the Sensor menu.
As the salinity of water increases, its ability to dissolve oxygen decreases. For
example, fully oxygenated 20 °C water at sea level with zero salinity will hold
9.092 mg/L of dissolved oxygen. If that same sample had a salinity value of 9
ppt, then it would hold 8.621 mg/L of dissolved oxygen. therefore, to obtain
accurate mg/L readings, it is important to know the salinity of the water you
will be testing and to input that value into the instrument. the salinity of fresh
water is typically 0-0.5 ppt and seawater is typically 35 ppt. You will also have
the opportunity to enter or modify the Salinity correction value during Do
calibration.
CALIBRAtIoN - DISSoLVED oXYGEN
the Pro Plus offers several options for calibrating dissolved oxygen: Do% in
water saturated air, Do mg/L and Do ppm in a solution of known dissolved
oxygen determined by a Winkler titration, and a Zero point. If performing a
zero point calibration, you must also perform a %, mg/L, or ppm calibration
following the zero calibration. For both ease of use and accuracy, YSI recommends
performing the following 1-point Do % water saturated air calibration:
It is not necessary to calibrate in both % and mg/L or ppm.
Calibrating in % will simultaneously calibrate
mg/L and ppm and vice versa.
Calibrating Do % in Water Saturated Air:
1-Point Calibration
the supplied sensor storage container (a grey sleeve for a single port cable or a
screw on plastic cup for the dual-port and Quatro cables) can be used for Do
calibration purposes.
Moisten the sponge in the storage sleeve or plastic cup with a small amount of
clean water. the sponge should be clean since bacterial growth may consume
oxygen and interfere with the calibration. If using the cup and you no longer
have the sponge, place a small amount of clean water (1/8 inch) in the plastic
storage cup instead.
Make sure there are no water droplets on the Do membrane or temperature
sensor. then install the storage sleeve or cup over the sensors. the storage
sleeve ensures venting to the atmosphere. If using the cup, screw it on the cable
and then disengage one or two threads to ensure atmospheric venting. Make
sure the Do and temperature sensors are not immersed in water. turn the
instrument on and wait approximately 5 to 15 minutes for the storage container
to become completely saturated and to allow the sensors to stabilize.
Press Cal . Highlight Probe ID or User ID
if you wish to add, select, edit, or delete an ID.
Probe ID must be enabled in the System GLP
menu to appear in the Calibrate menu. User
ID will appear automatically. Select ‘None’
if you do not want a User ID stored with the
calibration. When enabled, these IDs are stored
with each calibration record in the GLP file.
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