Teledyne API Model 200AU NOX Analyzer Instruction Manual, 02293, Rev. F
7-29
7.6.10 ZERO and SPAN Checks A system of Level 1 and Level 2 zero/span checks (see Table 7-1) is recommended. These
checks must be conducted in accordance with the specific guidance given in Subsection 9.1 of
Section 2.0.9 (Q.A. Handbook). Level 1 zero and span checks must be conducted every two
weeks. Level 2 checks should be conducted in between the Level 1 checks at a frequency desired
by the user. Span concentrations for both levels should be between 70 and 90% of the
measurement range.
Zero and span data are to be used to:
1. Provide data to allow analyzer adjustment for zero and span drift;
2. Provide a decision point on when to calibrate the analyzer;
3. Provide a decision point on invalidation of monitoring data.
Items 1 and 2 are described in detail in Subsection 9.1.3 of Section 2.0.9 (Q.A. Handbook). Item
3 is described in Subsection 9.1.4 of the same section.
Refer to the Troubleshooting Section 9 of this manual if the instrument is not within the allowed
variations.
7.6.10.1 Zero/Span Check Procedures
The Zero and Span calibration can be checked a variety of different ways. They include:
1. Manual Zero/Span Check
Zero and Span can be checked from the front panel keyboard. The procedure is in Section 7.1
of this manual.
2. Automatic Zero/Span Checks
After the appropriate setup, Z/S checks can be performed automatically every night. See
Table 6-2 and Section 7.3 of this manual for setup and operation procedures.
3. Zero/Span checks via remote contact closure
Zero/Span checks can be initiated via remote contact closures on the rear panel. See Section
7.5 of this manual.
4. Zero/Span via RS-232 port
Z/S checks can be controlled via the RS-232 port. See Section 5.5 of this manual for more
details.