Performing a Zero Calibration

From the Sensor Calibration screen, be sure that the button at the upper left of the instrument is selecting Zero Calibration and not Span Calibration. 

 

When this is selected, the target values will automatically go to zero.  Begin the flow of gas at the appropriate rate, and allow the readings to come to equilibrium.  This occurs when the actual values are not moving in a specific direction, and they display only slight movements up and down.  This should take approximately 45 seconds.

 

There is a column showing the Status of each gas.  In this area the instrument is making a comparison between the Target value and the Actual value and providing feedback based on the amount of difference between the two.  There are three possible words that can appear in this area:

 

“OK” – The gas is within 10% of where it is expected to be.

“OK?” – The gas is between 10% and 20% of where it is expected to be.  This could indicate an issue with the calibration gas, so the calibration gas and the associated tubing should be checked and verified to be free from leaks or improper gas composition.  This message does not necessarily indicate that there is a problem with the sensor or the calibration.  It is meant only to have the operator make sure that the proper procedures are being followed.

“BAD” – The gas is more than 20% from where it is expected to be.  The same items should be checked as described above.  This message could indicate an issue with the sensor.

 

Regardless of the status of each of the gases, the instrument can be calibrated by waiting for the readings to stabilize and pressing Start Calibration.  Timers will begin to count down, and when they reach zero the Actual values should be the same as the Target values (allowing for slight variations as a result of gas fluctuations).