Instruction manual

120-00004 REV A 10/6/2011 4000 DIGITAL MANUAL PAGE 11
Calibration
3.0 Introduction
All analyzers are factory calibrated prior to shipment.
There is no easy answer as to how often a monitor should be
calibrated. This is strictly a function of the application (gas
concentration and frequency of exposure to target gas). The
purpose for calibration is to compensate for any possible decrease
in sensor sensitivity. The primary cause of sensitivity decrease is
excessive loss of water by evaporation. A secondary cause may
be by contamination from unknown sources. H
2
S sensors show
an additional decrease in sensitivity due to internal sulfur
formation, the rate of which depends on the gas concentration.
3.1 INTERSCAN’S Electronic Calibration Service
The factory recommended procedure for calibrating all
INTERSCAN analyzers, involves the use of certified calibration
gas or a permeation device. Besides being essential for
calibration, having a known certified gas standard on hand allows
the user to test the analyzer at any time to determine that it “really
works”.
However, there will be times and circumstances in which
calibration using calibration gas or permeation devices is
inconvenient and costly. For this reason, INTERSCAN has
developed our alternative sensor revolving/certification program,
Electronic Calibration Service (ECS).
A certified spare sensor is kept at the customer’s site to be
installed into the analyzer, (after following the 7 steps on the ECS
certification) while the presently used sensor is sent back to the
factory for re-certification. The ECS certification, details zero and
span/cal adjustments that are to be made on the analyzer, to
match or coincide with the specified, newly certified sensor.