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2.3.3 Analyzer functional check
The analyzer functional check includes:
analyzer precalibration by atmospheric air oxygen;
check of readings in the null solution.
It is recommended that the analyzer functional check be performed:
after filling the sensor with electrolyte on delivery of the analyzer;
after replacement of the membrane assembly or teflon film;
if there are any doubts as to the analyzer’s serviceability.
2.3.3.1 Analyzer precalibration
Take the sensor out of the vessel with water and place it horizontally (put on
the table).
Press the
MODE
button
to enable the
DOC measuring mode
in
mg/dm
3
. The
analyzer display will show a figure measured in
mg/dm
3
.
Keep the sensor in the air for 5 min.
Press the
CAL
button twice. The analyzer display will show the
c1
symbol
showing the entry into the outside air calibration mode.
Press the
ENTER
button. The analyzer display will show DOC readings cor-
responding to the table of 100 % humidity air oxygen solubility for analyzer-
measured temperatures, with allowance for the atmospheric pressure at the time of
calibration, for example,
c8.38 mg/dm
3
.
Wait at least
8 s
before pressing the
ENTER
button once again. The
donЕ
caption will appear shortly on the screen and the
с
symbol will go out. The analyzer
will go into the measuring mode, which means that precalibration is completed.
2.3.3.2 Reading check in the null solution
Prepare an oxygen-free (
null
) solution, and for this purpose:
prepare an alkali solution (KOH or NaOH), concentration 5 g/dm
3
;
pour it into a 0,3-0,5 dm
3
vessel so that its level is 50 to 60 mm;
add 0,3 to 0,5 g of hydroquinone and stir.
Uptime in air tight vessel is max 1 month.
Submerge the sensor, with its membrane down, in the solution and move it
to slightly agitate the solution in order to prevent air bubbles from amassing on the
