Teledyne API Model 200AH NOX Analyzer Instruction Manual, 06492, Rev. G2
7-3

7.1. Manual NOX 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 in the sample
port. This method is often used when the calibration gas is supplied from the stack sample probe
or external tank and valve system. This is the calibration method to use if the instrument is
purchased without the Zero/Span Valve.
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. Check “Before
Calibration” Check “Before Calibration” Section 7 above before
proceeding.
2. Press CAL The M200AH enters the calibrate mode from sample mode.
The zero gas must come in through the sample port.
3. Select LO or HI
Range If AutoRange is enabled you will be prompted for which
range to calibrate. Select the LO or Hi range, then press
ENTR.
4. Wait 10 min Wait for reading to stabilize at zero value.
5. Press ZERO If you change your mind after pressing ZERO, you can still
press EXIT here without zeroing the instrument.
6. Press ENTR Pressing ENTR actually changes the calculation equations.
7. Press EXIT M200AH returns to sampling. Immediately after calibration,
data is not added to the DAS averages.