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Teledyne API Model 200AU NO
X
Analyzer Instruction Manual, 02293, Rev. F
5-14
5.2.2.2 Zero
Pressing the ZERO key along with ENTR will cause the instrument to adjust the OFFSET value
of the internal formula so that the instrument reads zero. The M200AU allows zero adjustment
over a limited range of signal levels, therefore the signal does not have to be exactly zero for the
instrument to do a zero cal. The instrument will not, however, allow a zero cal on any signal
level, therefore it is not possible to zero the instrument with high concentrations of span gas in
the reaction cell. If the ZERO key does not come on as expected, check Section 9.2.9.
5.2.2.3 Span
Pressing the SPAN key along with ENTR will cause the instrument to adjust the SLOPE value of
the internal formula so the instrument displays the span value. The expected NO
x
and NO span
concentrations must be entered before doing a SPAN calibration. See Table 7-3.
Like the Zero calibration, the Span cal cannot be done with any concentration of span gas. If the
signal level is outside certain limits the, SPAN key will not be illuminated. If you encounter this
condition see Section 9.2.8. It is also possible at low levels of span concentration that BOTH the
ZERO and SPAN keys might be on, thus allowing you to either zero or span the instrument. In
this case, care must be taken to perform the correct operation or the analyzer can become mis-
calibrated.
5.2.2.4 NO, NO
x
Cal Concentration
Before the M200AU can be spanned, it is necessary to enter the expected span concentrations for
NO and NO
x
. This is done by using CAL-CONC-NOX or CAL-CONC-NO keys for NO
x
and
NO span concentrations, respectively. Concentration values from 1 to 2000 ppb are valid