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 | Dashes: ‘----‘ |
| Measurement Gas to cell | |
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 O3 Monitor Operator Manual - Page 20