Advanced Instruments Inc.
not generate a current output in the absence of oxygen. Given the properties of linearity and an absolute zero, a
single point calibration is possible.
The analyzer is equipped with “Zero Calibration” feature. However, as described below, zero calibration is
recommended only when the application (or user) demands optimum accuracy of below 5% of the most sensitive or
lowest range available on the analyzer. For example, if the user requires analysis of a sample gas below 0.05%, zero
calibration may be required.
Span calibration, it is necessary to adjust the analyzer sensitivity for accurate measurements of oxygen by using a
standardized (certified) oxygen or by using ambient air (20.9%).
Zero
Calibration
Ideally, with no oxygen, the sensor should have zero signal but in reality, the analyzer may display oxygen reading
with a sample gas containing no oxygen (zero gas). Under such circumstance, it may be necessary to perform a Zero
calibration to remove any offset with oxygen free sample gas. The maximum zero offset correction is limited to a
maximum of 10% of the lowest (most sensitive) range for positive zero offset and 10% of the lowest range for
negative zero offset.
Zero calibration could be carried out before or after the span calibration. Normally, zero calibrations are performed
when a new sensor is installed or changes are made in the sample system connections. Allow the ZERO gas to flow
through the analyzer and wait until the signal has dropped to a low value and is stable.
Access the MAIN MENU by pressing the MENU key.
Advance the reverse shade cursor using the ARROW keys to highlight CALIBRATION.
Press the ENTER key to select the highlighted menu option.
The following displays appear:
MAIN MENU
SELECT RANGE
CALIBRATION
VIEW HISTORY
SYSTEM OPTIONS
>>>
CALIBRATION
SPAN CALIBRATE
ZERO CALIBRATE
DEFAULT SPAN
DEFAULT ZERO
OUTPUT CALIBRATE
OUTPUT SIMULATE
Advance the reverse shade cursor using the ARROW keys to highlight ZERO CALIBRATE.
Press the ENTER key to select the highlighted menu option.
The following displays appear:
0.15 PPM
ZERO CALIBRATION
WAIT FOR STEADY RDG
ENTER TO CALIBRATE
MENU TO ABORT
Wait until the analyzer reading stabilizes (depending on the history of the sensor, it may take a few minutes to
several hours) and then press the ENTER key to calibrate (or MENU key to abort).
If the offset is less than 10% of the lowest range, by pressing ENTER will pass the calibration and the analyzer will
return to the Sample mode. On the other hand, if the offset is above 10%, pressing ENTER will fail calibration and
the analyzer will return to Sample mode without completing the Zero calibration.
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