4. Disconnect any external tubing connected to the rear ports of the instrument (Sample Port,
Exhaust Port, etc.).
5. Wait 2-5 minutes and enter the ambient barometer reading into the instrument - Accept.
Figure 46 – Setting the Ambient Set Point
Note: All three sensors should now be displaying the current ambient pressure and they should be
the same value within 3 torr of each other.
6. Back - Pressure Calibration Menu - (read note) - OK.
5.3 Zero Calibration
Zero checks and calibrations are used to determine the zero response of the instrument and set the
offset of the instrument if required.
Performing a zero calibration will adjust the Zero Offset NO, NO2 and NH3. These offsets can be
checked in the Main Menu Service Menu Calculation Factors Menu and should be very close
to zero. A large offset may indicate a problem with the instrument (refer to Section 7).
Note: Ecotech encourages regular zero precision checks; however Ecotech recommends that the zero
calibration only be performed when specifically required as it may mask issues that should be
addressed during maintenance/service.
A zero calibration can be performed either through the Calibration Port, Background Air Port or the
Sample Port. Refer to the instructions outlined in the next three sections:
5.3.1 Calibration Port
Equipment Required
Zero source
Note: Ensure the instrument has been running for at least one hour before any calibration is
performed to ensure sufficient stability.
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