AMI Analyzer Manual
Installation Procedure
12
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 bypass time when you press that button – it
shows what the bypass 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 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 sensor to come back down to a low reading on the sample.
Then perform a span gas calibration only don’t adjust the span factor with the UP or
DOWN buttons, and see what the analyzer says the gas contains. If the gas value isn’t
what you think it should be, it is the gas that is wrong, not the analyzer, because that air
calibration is in fact very valid. You will have to trouble shoot whatever has happened
with your gas.
Output range concept:
The analyzer displays the oxygen level in appropriate units on the LCD, automatically
adjusting its sensitivity as required. Meanwhile the analog output and the alarms are set
on a single (user selectable) “Output” range.
For example, you can set the analog output to correspond to 0-100ppm, and the alarms
to be say 40ppm and 50ppm (i.e. 40% and 50% of range), activating above set point. If
the oxygen level actually is 25ppm, the display will show 25.0ppm, and the output signal
will be at 25% of full scale. If the oxygen level becomes 200ppm, the display will show
200ppm, but the 4-20mA output will be saturated, and the alarms will both be activated.
If you now manually change the output range to 0-1000ppm, the reading will stay at
200ppm, the 4-20mAoutput will go to 20% of scale, and the alarms will de-activate, since
they now correspond to 400ppm and 500ppm, i.e. still 40% and 50% of range.
Front Panel Controls:
The controls all work the same way. You press the function you want for a second, and
let go, and the display will show the value corresponding to that function, for about 3
seconds. For example, if you press the OUTPUT RANGE button for a second, the display
will show the full scale output range. You can change this value (if the security setting
allows) by then pressing the UP or DOWN arrow button within about three seconds. You
can either press this once for a small change, or you can hold it down, in which case the
number will change slowly at first, and then faster. If you overshoot your target, press
the other button to go back, and the display will again start moving slowly. If you release