Hach 8450, Инструкция по эксплуатации инструмента

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Section 3
Page 37
16116Operation.fm
Span Calibration
In preparation for zero calibration, fill a beaker with approximately 2" of
deionized water. Place the beaker into a tub (or sink) and permit the sample
stream to flow around it until the temperature of the deionized water is same
as the sample stream. Take care not to let any of the sample stream water mix
with the deionized water. Remove the probe from the flow cell or flow stream
and place it into the deionized water, being careful to prevent the membrane
tip from contacting the bottom surface. Allow the displayed reading to stabilize
and then perform the zero calibration as outlined below.
3.14.3 Zero Calibration Procedure
1. When all preparations are complete, select the icon to display the Main
Menu. Move the cursor to “CAL” and select
E
. Move the cursor to the
ZERO menu and select
E
. Observe that any active alarms are
immediately cleared and the CHECK alarm is activated (unless previously
inhibited in the Alarms menu). At this point, the VMA outputs and data
logger are held at the last reading, and alarms are inhibited.
2. Remove the probe from the flow cell or flow stream and immerse it in the
zero solution. Wait for the displayed reading to stabilize to its lowest final
value. This will be evident when the reading appears to be varying above
and below a final low value. These variances must be less than 0.02 ppm
over 60 seconds before the instrument will accept the reading as stable. If
required, increase the DAMP parameter in the RDG menus screen (see
section 3.22 on page 43 ).
3. When stable, select
E
. At this point the timer will set to 10 minutes and
begin counting down while the instrument monitors the stability of the
probe signal. If you have already observed a stable reading as required in
step 2, this check will normally take about 2 minutes. When the stability
check is finished, the message “Zero Cal Complete...” will be displayed
until acknowledged by selecting
F
to exit to ZERO / SPAN menu;
E
to
restart the ZERO calibration. Selecting
E
anytime during the check will
bypass the stability check and present a “Zero Cal Completion” message;
however, this may lead to inaccurate calibration.
If the timer to expires (00:00), the calibration will be aborted and a
message will be displayed until acknowledged by selecting a front
panel icon. If this occurs, navigate the cursor to the “RDG” menu,
enter it, and increase the “DAMP” parameter to 10 seconds. Repeat
Steps 1 through 3.
4. Place the probe back into the flow cell or flow stream and select the
F
icon
to return to ZERO / SPAN menu or
E
to restart calibration. The *CHECK*
screen will be displayed until both the Zero and Span calibration have
been performed at least once.
3.15 Span Calibration
For span calibration, the probe is immersed in a solution of known chlorine
concentration. The operator enters the known concentration into the meter via
the front panel controls, and the meter automatically adjusts itself so that the
probe indicates this concentration. During the calibration the meter checks the
probe signal’s stability and amplitude and will prevent completion of the
calibration unless the signal is within prescribed parameters.