AMI Analyzer Manual
Maintenance and troubleshooting
31
A sure sign of a problem is an unexpected span factor. Check the span factor by pressing the UP button
immediately after performing a calibration. If this number is below about 350 it indicates that you have
spanned the sensor too low – either you have more oxygen than you think in your span gas, or the sensor
hasn’t equilibrated to a change in temperature yet. If the number is much greater than the last time the
analyzer was calibrated, either the sensor has reached the end of its life or there is some other calibration
error. Using the user interface, you can read the previous span factors as well. This number always goes up
as the sensor ages (it is changed every time you span the analyzer, it doesn’t change by itself). So if it goes
down, something is wrong. You have more oxygen in the span gas than you thought, (or there is something
wrong with the analyzer, but this doesn’t happen often).
Analyzer does not power up.
1. Check that the power is connected correctly, and that you have the appropriate version for your power
supply.
2. Check that the power supply voltage is between 10V and 28VDC, or else it is 117VAC (plus or minus
10V).
3. Verify that the power plug is seated in its socket all the way, and that no whiskers of wires are shorting
to each other or to the cover.
4. If the user interface can talk to the analyzer, but nothing shows on the LCD, the analytical board or the
connection to it has failed.
5. If the LCD shows a number, and once a minute shows “Err”, the power board has failed or the internal
communication has failed.
Analyzer reads too low
1. Sensor may not be calibrated. Flow span gas through it and span the analyzer until the analyzer reads
appropriately.
2. If the span factor is now too high (up about 999 or so), or if you cannot adjust the span enough to
accomplish this, replace the sensor.
3. If the new sensor still reads too low, check its calibration with air and read the span gas - the span gas
may be incorrect.
4. If the sensor seems to die quickly, it may be getting poisoned by acid or sulfur bearing gases such as H
2
S.
If so, use a higher H
2
S rated sensor such as a P-5.
5. Verify that the cell block connectors are in fact making contact with the cell. Clean them gently with a Q
tip, and bend them slightly down so that they make a good contact. Once this is done the cell should
have some resistance to being removed from the block.
6. Water may have shorted out the contacts on the back of the sensor. If so, use a Liquid Rejection Probe
with an AMI demister or coalescing filter to make sure that condensation does not occur within the
analyzer.