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4.2 Auto-Zero Operation
The Auto-Zero feature allows the monitor to operate unattended for extended periods of
time. This feature automatically performs a Zero Calibration at specific intervals (default
interval is 12hrs.) The monitor does this by opening a solenoid valve to allow externally
supplied Zero Gas to purge the monitor and then automatically performs a Zero
Calibration.
4.2.1 Auto-Zero Installation
In order for this feature to function properly, external, pressurized zero gas must be
supplied to the monitor as detailed in Section 2.2.
4.2.2 Auto-Zero Function
When the Auto-Zero function is triggered, the monitor performs the steps outlined in
Table 4-1 below.
Table 4-1 Auto-Zero Function
Step Function Display Reads
1 Switch Auto-Zero valve on N/A
2 Purge cell for 20 seconds Holds and Flashes Concentration Value
3 Perform Zero Calibration Dashes: ‘----‘
4 Switch Auto-Zero valve off Dashes: ‘----‘
5 Hold-Off for 3 sec to return
Measurement Gas to cell
Dashes: ‘----‘
6 Return to Measurement Mode Normal Concentration Display
4.2.3 Auto Zero Error
When performing an Auto-Zero Calibration, the monitor checks to make sure the ozone
concentration is near zero before calibration. If the ozone concentration is above 0.5wt%
or 5.0 g/Nm3, the monitor will not perform the calibration and will display a “ZERO
ERR” message on the display. The monitor will also turn on the Auto-Zero Error status
signal (See Section 2.4.2 Digital Status Outputs.) This Status Signal will remain on until
another Auto-Zero Calibration is successfully performed or a Manual Zero Calibration is
performed.
If an Auto-Zero error is detected, a manual Zero Calibration should be performed (See
Section 4.1.3 Zero Calibration.)
P/N 03662D Teledyne API Model 460H O
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Monitor Operator Manual - Page 20