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Section 3
3.13.5 Operational Considerations
Figure 24
ZERO or SPAN Calibration Menu Items (Typical)
3.14 Zero Calibration
3.14.1 Preparation
3.14.2 Optimizing Zero Calibration
Page 36
Zero Calibration
If the instrument software is password locked, you will not be permitted into
the ZERO or SPAN calibration menu. Instead, you will be prompted by the
instrument to first enter the password.
In order to prevent false alarms, enter into the specific instrument calibration
routine before subjecting the probe to the calibration concentration. Upon
entry into either the ZERO or SPAN menus:
•
The CHECK alarm will be set immediately (no delay).
•
If either ALARM 1 or ALARM 2 is active, it is cleared and inhibited until
exit from the menu.
Note: The CHECK alarm may be inhibited by setting the 'i' bit in the alarm's 'lfit' field
(see
section 3.17.4 on page
outputs will be held at their last readings until exiting the menu, or after screen
time-out.
When a calibration has been initiated, the (screen) time-out feature is
disabled. It is only re-enabled by aborting the procedure (using the icon) or
acknowledging the complete message (using the icon) at the end of the
sequence.
A typical zero/span calibration screen is depicted in the figure below. The
scrolling message area provides instructions to the operator during
calibration.
Scrolling message...
> 0.00 PPM
During zero calibration, the probe is immersed in a solution free of any
chlorine.
Zero-Chlorine Water
Deionized water is preferable when zeroing the probe, however, distilled water
may be used. If deionized or distilled water is not available, bottled drinking
water may be used after it has been allowed to outgas for 10–15 minutes any
dissolved gases which may be present. Tap water may also be used if it is
boiled for 15 minutes and allowed to cool.
Container
A beaker large enough to hold the probe and some water will be required.
In general, the speed and accuracy of calibration may be improved when
ZERO and SPAN calibrations are done at the SAME TEMPERATURE. To
achieve this, a bath may be used to equalize the deionized water to the
sample stream temperature.
41). During this time, signals on the VMA analog
T-0:00
101%
16116Operation.fm
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