Servomex Xentra 4900 User Manual

4.1
SECTION 4 CALIBRATION
4.1 Introduction to calibration
The calibration of the analyser may be checked or adjusted. Either of these activities
will result in an entry in the calibration history log.
Calibration may be manual or automatic. In manual calibration the operator is guided
through the required sequence of steps by messages on the xentra screen. Each gas
sensor module must be calibrated separately and each type has its own user interface
as detailed later.
When the optional external autocalibration or internal autocalibration manifold are fitted,
a manual calibration adjustment or calibration check will use the autocalibration valves
to select the calibration sample gases as required. It is important to note that different
calibration gases may be used to LOW and HIGH calibrate each transducer. Also the
gas used to LOW calibrate one transducer may be used to HIGH calibrate another. The
calibration gas ( CAL1 or CAL2 ) that is to be used as LOW and HIGH calibration for
each transducer is set up in the autocalibration parameters set up menu. The
procedure for setting the gases to be used as LOW and HIGH calibration is given in
section 4.9 ( see also table 4.7 ).
If the analyser is still warming-up (as indicated by the warming-up icon) and a
calibration is attempted, a warning message will be given with an option to proceed.
The warming up icon indicates that at least one of the fitted gas sensor modules is still
warming up. The transducer that the user may wish to calibrate may, of course,
already be at its operating temperature and be capable of calibration even though the
warming up icon is still displayed. The warming-up icon will normally have cleared
within 1 hour. The warming-up icon clears when all gas sensor modules are within
temperature band. For optimum performance, a further period of time should be
allowed for the gas sensor modules to reach final temperature before performing
calibration. This may take up to 6 hours.
Alternatively, calibration checking and calibration adjustment may be performed
automatically provided that either the internal or external auto calibration options are
fitted. The auto calibration options appear in the user interface menus only when the
relevant hardware is fitted. When an automatic calibration is performed then all of the
gas sensor modules selected will be calibrated simultaneously.
The auto calibration process can be initiated in three ways: by an internal timer; by an
external contact closure; or by operator request through the user interface. Details of
each are given in sections 4.10 to 4.12. If any one of these events occurs while the
auto calibration cycle is in progress the request will be ignored. Touching the keypad
during auto calibration will initiate the abort sequence (section 4.13).
The instrument will only respond to a request for auto calibration from the internal timer
or external input if there are no faults indicated. Auto calibration can be initiated from
the user interface when there is a fault condition.
If auto calibration or auto check is to be disabled see section 4.11 ’Disabling auto
calibration’.

Servomex Xentra 4900 Specifications

General

Brand	Servomex
Model	Xentra 4900
Category	Analytical Instruments
Language	English