VOXI User’s Guide
14
5.4.1 Calibration
1.
Initiate a
Zero Calibration
by clicking on the icon. When prompted, supply clean air
to the inlet and click ‘Yes’ to start the count-down timer. If the VOXI is mounted in an area
where ambient air contains detectable VOCs, provide a clean air source a) by attaching a
charcoal filter, b) attaching a gas bag (e,g, Tedlar
®
bag) filled with about 1 liter of clean air
from a cylinder, or c) clean air directly from a cylinder fitted with either a demand-flow
regulator or a fixed-flow regulator of about 0.5 LPM.
2.
Before zero or span calibration, it is good practice to examine the water trap filter and large
secondary filter inside the housing for cleanliness and replace as needed.
3.
Initiate a
Span Calibration
by clicking on the icon. When prompted, supply span gas
to the inlet and click ‘Yes’ to start the count-down timer. Span gas can be supplied either
from a gas bag (e,g, Tedlar
®
bag) filled to at least 1 liter, or directly from a gas cylinder
fitted with either a demand-flow regulator or a fixed-flow regulator of about 0.5 LPM.
4.
The
Zero
or
Span Calibration
can be
aborted
at any time during the countdown by click
on the gas bottle icon again while it is red.
5.
Use of fixed-flow regulators below 0.5 LPM or above about 0.6 LPM will cause poor
calibration. A regulator with flow higher than 0.6 LPM can be used if an open T fitting is
placed in line between the regulator and VOXI inlet to allow excess gas flow to escape
without being forced through the instrument.
6.
The
Calibration Interval
must be defined by the user because it depends on the
application and local conditions. We recommend starting with weekly bump tests to
check the response of the PID and need for filter changes, and then increasing the length of
time between checks and calibrations as experience is gained in the application. We
recommend no longer than 6-month intervals between calibrations.
Zero Calibration screen
Span Calibration screen
Aborting a Calibration
