and assayed with a UV calibration photometer at the time of use or they may be obtained by means
of a certified transfer standard.
There are several different types of checks/calibrations performed:
Level 1 Calibration – A simplified two-point instrument calibration used when instrument linearity
does not need to be checked or verified. This check is typically performed on a monthly basis.
Adjustments to the instrument response can only be made when performing level 1 calibration.
Level 2 Calibration – A simple check of the instrument’s response. Level 2 checks may be performed
using non-certified reference sources and are most often used as a performance monitoring tool.
The instrument may not be adjusted
Multipoint precision check – A series of calibration points, typically covering zero and 5 up-scale
points, measured using a certified reference atmosphere and covering the instruments FS
measurement range. These precision checks are used to determine the linearity of the instrument
response across its measurement range.
In general terms, the calibration process includes the following steps:
1. Establish a reliable and stable calibrating source.
2. Provide a satisfactory connection between the calibration source and the instrument.
3. Calibrate the instrument against the calibration source.
Multipoint precision check is used to establish the relationship between instrument response and
pollutant concentration over the instrument's full scale range. Zero and span calibrations are
frequently used to provide a two-point calibration or an indication of instrument stability and function.
Note: Zero calibrations are not recommended by Ecotech, but maybe be performed when
specifically required by a user. Zero calibrations tend to mask issues that should be addressed
during maintenance/service.
Regulations generally require that the instrument be span calibrated any time:
The instrument is moved.
The instrument is serviced.
When changing the instruments units between volumetric and gravimetric.
Whenever the instrument characteristics may have changed.
Regulatory agencies establish the time intervals at which the instrument must be calibrated to ensure
satisfactory data for their purposes.
Note: Use of the Serinus 10 O
3
analyser as a U.S. EPA or EN-designated equivalent method requires
periodic multipoint precision checks in accordance with the procedure described below. In
addition, the instrument must be set to the parameters indicated in U.S. EPA (refer to Section 2.4)
or EN Equivalent Set-up (refer to Section 2.5).
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