AMI Analyzer Manual
Installation and Operation
8
Calibration
The analyzer must be calibrated every 180 days.
The calibration of the analyzer shall be accomplished using three different primary standards of oxygen in
nitrogen within the ranges specified below to establish the analyzer accuracy and linearity:
1. 3% +/- 1% oxygen in nitrogen.
2. 10% +/- 4% oxygen in nitrogen.
3. 20.9% +/- 1% oxygen in nitrogen.
The above three primary standard gas mixtures shall be traceable to NIST and have uncertainty of +/-1% of component
or +/-0.02% of absolute, whichever is lower.
During calibration, any tubing used should be of high quality plastic such as Teflon or Tygon or other hard plastic, not
soft silicone tubing as this latter is highly permeable to oxygen.
To calibrate:
1.
Flow the high level (20.9%) span gas through the analyzer at 1SCFH, adjusting as necessary with the
valve.
2.
Let the reading stabilize for approximately 2 minutes.
3.
If the value shown by the analyzer is incorrect, press the SPAN button.
4.
Within 3 seconds, press the Up or Down arrow button and watch the reading change.
5.
When it has reached the desired level, release the button.
6.
Flow the mid level (10%) gas through the analyzer at the same 1SCFH rate, adjusting as necessary with
the valve.
7.
Let the reading stabilize for approximately 2 minutes.
8.
Verify that the analyzer reads the correct value as shown on the span tank bottle, +/- 0.14% O
2
.
9.
Flow the low level (3%) gas through the analyzer at the same 1SCFH rate, adjusting as necessary with
the valve.
10. Let the reading stabilize for approximately 2 minutes.
11. Verify that the analyzer reads the correct value as shown on the span tank bottle, +/- 0.14% O
2
.
12. If either of the two lower gases read outside the limits, adjust the span so that all three gas values are
/- 0.14% O
2
. For example, if the unit reads exactly correctly at 20.9%, but reads 3.15% with 3%
gas, turn the span down a little so that it reads 19.9% with the high level gas, and 3.14% with the low
level gas. You may have to go back and forth a few times to get this right.
Once you let go of the SPAN button, after a few seconds the “SPAN” flag on the display will go out and the unit will
store the new span coefficient in its non-volatile memory
Note: It is possible to disable the calibration function with the USB interface. If it is not apparently possible to change
the calibration, you must reset the security condition to “All front panel adjustments allowed” using the AMI user
interface. Perform the calibration as above, and then change it back to “No front panel adjustments allowed” when you
are done.
