5.6 Precision Check
Similar to a normal zero or span calibration, a precision check is a Level 2 calibration that may be
performed using a non-certified reference. The instrument is supplied with a known concentration of
span gas (or zero air) and the instrument’s response observed. However, no adjustment to the
instrument response is made during a precision check.
A precision check can be performed either manually via the Sample Port, Calibration Port or
Background Port (Zero Only) or can also be performed automatically using the Timed Mode (refer to
Section 3.4.10.2).
Equipment Required
• Span source
• Zero source
Procedure
1. Supply the instrument with a zero source (refer to Section 5.4 for the procedure of setting up a
zero, but do not do a Zero Calibrate CO, and continue following below steps).
2. Observe and record the measurement from the instrument.
3. Supply the instrument with a span source (refer to Section 5.5 for the procedure of setting up a
span but do not do a Span Calibrate CO).
4. Observe and record the measurement from the instrument.
5. Check both readings against user local applicable standards.
6. Select - Cal. Mode → Measure - Accept (To return to sample measure).
If an instrument fails a span precision check (based on the users local applicable standards), perform a
span calibration (refer to Section 5.5).
If an instrument fails a zero precision check (based on the users local applicable standards), resolve the
issue by referring to Section 7 Zero Drift.
5.7 Multipoint Precision Check
A multipoint precision check is used to determine the linear response of the instrument across its
operating range. The instrument is supplied with span gas at multiple known concentrations, typically
a zero point and at least five up-scale points, spread across the operating range of the instrument. The
observed concentrations are compared to expected values and the linearity of the instrument assessed
against local applicable standards.
Note: The instrument is inherently linear and the instrument gain should not be adjusted at each
individual point. Non-linearity indicates a problem with the instrument (refer to Section 7). Ensure
that the instrument has been running for at least one hour before any calibration is performed to
ensure sufficient stability.
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