119
TROLL
9500
Operator’s Manual
0095110 rev. 007 01/09
12. Remove the Cal Cup, discard the first solution, rinse the Cal Cup
and the front end of the instrument with clean water, followed by
a rinse in the next calibration solution, refill the Cal Cup with the
second solution, and attach it to the instrument.
TIP:
The used calibration solution may be flushed down the
drain with running water, or saved in a separate container
and used as a rinse the next time you calibrate with the
same solution.
13. Select
Run
to begin the stabilization for cal point 2. Status indica-
tors and controls are the same as for cal point 1 (step 10).
Again wait for Stable status (or click Accept when Nominal is
indicated).
If doing a two-point calibration, go to step 16.
14. For the third calibration point, use the cal point 1 or cal point 2
solution (as specified in step 8) but change the temperature by at
LEAST½#!CONVENIENTWAYTODOTHISISTOMOVETHEPROBE#AL
Cup and all—into a temperature-controlled bath or container of
ice. Allow time for the sensor to reach thermal equilibration with
the solution temperature. With stirring or agitation, this should take
about 10 minutes, perhaps up to 30 minutes if left undisturbed.
15. When the temperature is stable, select
Run
for cal point 3.
When Nominal is accepted or Stable is indicated for cal point 3,
the final screen is displayed.
16. The final screen of the Calibration Wizard shows the sensor
slope and offset calculated during the calibration process. For a
three-point bithermal calibration, the calculated isopotential point
is shown. If a single-point calibration has been performed, the
isopotential point is the one calculated during the last three-point
bithermal calibration.
17. Select
Finish
to program the sensor with the newly calculated
calibration coefficients.
The nitrate sensor is now calibrated and ready to use.
TIP:
You can look at the calibration report right after
calibrating, or at any time. See “Calibration History” in
Section 10 for details.
Options for storing sensors:
The sensor should calibrated immediately before use. If storage is
necessary, remove the sensor from the instrument and immerse in 14
ppm N solution, for later use in the low nitrate range, or 140 ppm N
solution, for use in the high range.
SENSOR SLOPE AND OFFSET
The expected slope for a new sensor is about 57 (± 2) mV per decade
of concentration (ppm). The calibration curve begins to deviate from
linear at about 10 ppm. The sensor’s zero offset is recalculated with
each single-point calibration.
UNITS AND CALCULATED MEASUREMENTS
Nitrate ion concentration is reported in ppm (equivalent to mg/L). No
calculated measurements are available.
USAGE RECOMMENDATIONS AND CAUTIONS
Nitrate Sensor
/PERATING4EMPERATURE
½#TO½#½&TO½& CONTINUOUS
TEMPERATURECANTOLERATEUPTO½#
½& INTERMITTENTLY
Pressure Rating
20 psi (14 m, 46 ft)
pH range
2.5 to 11
Do not submerge the nitrate sensor deeper than 46 ft
(14 m).
TEMPERATURE
The higher the temperature, the shorter the lifetime of the electrode.
½#DIFFERENCEINTEMPERATURECAUSESAERRORATPPMUNLESSA
bithermal calibration is performed.
SECTION 17: NITRATE
17