Teledyne 460H Auto-Zero Operation, Auto-Zero Installation, Auto-Zero Function, Auto Zero Error

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