Figure 9-1. Flow Diagram, Zero/Span Option - Thermo Scientific 42i Instruction Manual

Optional Equipment
Internal Permeation Span Source
Internal Permeation
Span Source
9-2 Model 42i Instruction Manual
Figure 9–1. Flow Diagram, Zero/Span Option
The Internal Permeation Span Source option is designed to provide a
simple source of span gas. It is intended as a quick, convenient check to be
used between zero and span calibrations for determining instrument
malfunction or drift. Because this option does not precisely control dilution
gas flow, it should not be used as a basis for instrument zero and span
adjustments, calibration updates, or adjustment of ambient data.
Whenever there is an indication of instrument drift or malfunction, a full
zero and multipoint calibration (Level 1) should be performed prior to
corrective action. For further information on zero, span and calibration of
air pollution monitors, refer to Section 2.0.9 of the US EPA's Quality
Assurance Handbook for Air Pollution Measurement Systems (Volume II).
Figure 9–2 shows how this option is integrated with the Model 42i
components. Energizing the sample valve V1 shuts off the sample flow and
permits the flow of zero air for analysis. When valves V1 and V2 are
energized, the flow of zero air mixes with air containing NO
permeation oven. This mode of operation provides a single point span
check.
from the
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