Teledyne 6200T - Sulfides Analyzer - Manual (Page 217)

6200T Total Sulfur Analyzer EPA Protocol Calibration
Teledyne Analytical Instruments 217
Table 10-4: Definition of Level 1 and Level 2 Zero and Span Checks
(Refer to Section 2.0.9 of Q.A. Handbook for Air Pollution Measurement Systems)
LEVEL 1 ZERO AND SPAN CALIBRATION
A Level 1 zero and span calibration is a simplified, two-
point analyzer calibration used when analyzer linearity
does not need to be checked or verified. (Sometimes
when no adjustments are made to the analyzer, the
Level 1 calibration may be called a zero/span check, in
which case it must not be confused with a Level 2
zero/span check.) Since most analyzers have a reliably
linear or near-linear output response with concentration,
they can be adequately calibrated with only two
concentration standards (two-point concentration).
Furthermore, one of the standards may be zero
concentration, which is relatively easily obtained and
need not be certified. Hence, only one certified
concentration standard is needed for the two-point (Level
1) zero and span calibration. Although lacking the
advantages of the multipoint calibration, the two-point
zero and span calibration--because of its simplicity--can
be (and should be) carried out much more frequently.
Also, two-point calibrations are easily automated.
Frequency checks or updating of the calibration
relationship with a two-point zero and span calibration
improves the quality of the monitoring data by helping to
keep the calibration relationship more closely matched to
any changes (drifts) in the analyzer response.
LEVEL 2 ZERO AND SPAN CHECK
A Level 2 zero and span check is an "unofficial" check of an
analyzer's response. It may include dynamic checks made
with uncertified test concentrations, artificial stimulation of the
analyzer's detector, electronic or other types of checks of a
portion of the analyzer, etc.
Level 2 zero and span checks are not to be used as a basis
for analyzer zero or span adjustments, calibration updates, or
adjustment of ambient data. They are intended as quick,
convenient checks to be used between zero and span
calibrations to check for possible analyzer malfunction or
calibration drift. Whenever a Level 2 zero or span check
indicates a possible calibration problem, a Level 1 zero and
span (or multipoint) calibration should be carried out before
any corrective action is taken.
If a Level 2 zero and span check is to be used in the quality
control program, a "reference response" for the check should
be obtained immediately following a zero and span (or
multipoint) calibration while the analyzer's calibration is
accurately known. Subsequent Level 2 check responses
should then be compared to the most recent reference
response to determine if a change in response has occurred.
For automatic Level 2 zero and span checks, the first
scheduled check following the calibration should be used for
the reference response. It should be kept in mind that any
Level 2 check that involves only part of the analyzer's system
cannot provide information about the portions of the system
not checked and therefore cannot be used as a verification of
the overall analyzer calibration.