Teledyne API Model 200AU NOX Analyzer Instruction Manual, 02293, Rev. F
7-4
7.1 Manual Zero/Span Check or Cal with Zero/Span Gas in the Sample Port
The calibration of the instrument can be checked or adjusted using gas coming through the
sample port. This method is often used when the calibration gas is supplied from an external
calibrator and valve system.
This is the calibration procedure to use if the instrument is purchased without the Zero/Span
Valve option.
Since the zero gas concentration is defined as 0 ppb, it is not necessary to enter the expected zero
value. Table 7-2 details the zero calibration procedure with zero gas coming in through the
sample port.
Table 7-2: Manual Zero Calibration Procedure - Zero Gas thru Sample Port
Step Number Action Comment
1. Press CAL The M200AU enters the calibrate mode from sample mode.
The zero gas must come in through the sample port. When the
CAL button is pressed, the adaptive filter is activated. This
allows the instrument to respond rapidly to concentration
changes regardless of their magnitude.
2. Wait 10 min Wait for reading to stabilize at zero value or for STABIL
reading to get to < 2 ppb.
3. Press ZERO If you change your mind after pressing ZERO, you can still
press EXIT here without zeroing the instrument.
4. Press ENTR Pressing ENTR actually changes the calculation equations.
5. Press EXIT M200AU returns to sampling. Immediately after calibration,
data is not added to the DAS averages.