In-Situ TROLL 9500 Operators Manual - Manual (Page 92)

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TROLL 9500 Operator’s Manual 0095110 rev. 007 01/09
20. When readings have stabilized (or you Accept the Nominal
value), the final screen is displayed. The calculated sensor slope
and offset are shown.
21. Select Finish to program the sensor with the new calibration coef-
ficients. The values will be written to the sensor and you will be
asked if you want to see the calibration report.
TIP: You can look at the calibration report right after
calibrating, or at any time. See “Calibration History” in
Section 10 for details.
Rinse the sensor and front end of the instrument very thoroughly after
calibrating in sodium sulfite solution. A good way to do this is to fill the
Cal Cup with water, attach to instrument, and shake vigorously. This
may need to be done a couple of times.
TIP: The calibration solution may be flushed down the drain
with running water, or saved in a separate container and
used to rinse the sensors the next time you calibrate with the
same solution.
After everything is thoroughly rinsed, the D.O. sensor is ready se.
Options for storing the sensor:
We recommend you leave the D.O. sensor installed in the instru-
ment; this will assure you are able to take fast D.O. measurements on
demand. A little water (distilled, deionized, or tap) or a damp sponge in
the Cal Cup will keep the sensor membrane moist.
Remember that, as long as the D.O. sensor is installed, it is being
conditioned.
If the sensor is removed from the instrument and then re-installed,
conditioning will begin as soon as the sensor is detected by the instru-
ment and displayed in the software.
SENSOR SLOPE AND OFFSET
The slope of a properly functioning sensor as calculated during the
calibration process will typically be in the following ranges, depending
on the membrane thickness:
1-mil membrane: between 30 and 67 nA/(mg/L)
2-mil membrane: between 15 and 34 nA/(mg/L)
If the calculated slope is much outside the stated range, the sensor
may need maintenance. Refer to
“Sensor Care and Handling” below.
The default offset for Quick Cal and 1-point calibrations is 2 nA.
Offsets for 2-point calibrations should fall under 10 nA.
UNITS AND CALCULATED MEASUREMENTS
Four units are available for dissolved oxygen:
TIP: To change unit preferences: In Win-Situ, select
Preferences on the Options menu. In Pocket-Situ, select the
Home site, then tap Setup in the command bar.
s
(mg/L). Since a liter of pure water weighs 1000 grams, and a
milligram is 1/1000 of a gram, this is equivalent to ppm (parts per
million).
s
(μg/L).
s
s
of oxygen that can be dissolved in water at a given atmospheric
pressure, water temperature, and salinity. % saturation output is
automatically corrected using the TROLL 9500’s temperature,
conductivity, and barometric pressure values (from a baro sensor
on vented cable or from a user-entered input). If no conductivity
sensor is present, salinity is assumed to be zero.
SECTION 13: DISSOLVED OXYGEN—POLAROGRAPHIC
Why does it take so long for the D.O. 100% to stabilize in
air?
Paying attention to several factors can assure the shortest
stabilization times possible within the stability algorithm:
s
s
If these conditions are met, the sensor response should stabi-
lize in 6-15 minutes.
20
A:
Q: