AMI Analyzer Manual
Analyzer Description
25
Calibrating with a span gas
Fist put a suitable regulator on the span gas tank. Connect the regulator to the analyzer with a flexible line
such as that provided by AMI, and leak check the connection with “Snoop™” or similar leak detection fluid.
Purge the line for several minutes with a small flow of gas prior to doing this, and leave the gas flowing while
you make the connection to the analyzer. This prevents a slug of air from giving you excessively high
readings when you start spanning the analyzer.
Make sure the analyzer is seeing a low oxygen level gas – you want the analyzer to go UP to the span gas,
not down to it, particularly not from air. Otherwise it can take a long time to get a good calibration.
When all is assembled, turn the flow selector valve on the front of the analyzer to the SPAN position. Span
gas is now flowing into the analyzer, and you should see the reading move to the span gas value. Assuming
it stabilizes somewhere reasonably close, press the UP or DOWN button until the reading on the LCD shows
what the span gas bottle says the value should be. Let go of the buttons, and after a second or two the
analyzer will store its calibration value. Return the flow selector valve to the SAMPLE position.
Calibrating with air
You can either connect a compressed air line – from the plant air, not a bottle of compressed air – to the
span port or you can leave the span port open. If you use compressed air, go through the same procedure
as above, only adjust the oxygen reading to 20.9%.
If you do not have compressed air, turn the flow selector valve to OFF, and unscrew the cell cap on the front
of the analyzer. Blow some air under the sensor by waving a hat or some such at it. Adjust the reading as
before to 20.9% and then turn the flow selector valve back to SAMPLE. Then screw the cell cap back on the
analyzer.
Alarm Bypass
Press the alarm bypass button prior to calibration if you have the alarms attached to anything, so as to stop
them from going off when the analyzer sees the high oxygen level in the calibration gas. You can adjust the
hold off time when you press that button – it shows what the hold off time is, and you can change it with
the UP or DOWN buttons as desired. The analog output will also be held constant during this time.
Span problems
Sometimes you will run into problems. If the sensor is old, it may not be able to come up to the span gas
level. If so, you need a new sensor. Sometimes the sensor will calibrate on span gas but will fail on air. This
also indicates an old sensor. You can see the sensor state by pressing the UP button when the sensor is
showing the oxygen level – it displays the “Span factor”, a number between about 450 and 1000. As the
sensor gets old each calibration will increase this number and when it gets up to about 850 it is time to
replace the sensor.
Sometimes the sensor won’t calibrate on span gas properly, but since it is a new sensor you figure
something must be wrong. If something like this is happening, perform an air calibration and allow the