8-A-4 Chapter 8: Gas Analyzer Calibration 42/24-10 EN Rev. 9
Automatic Calibration
Definition Automatic calibration means:
Zero and span calibration run automatically after starting.
Test Gas Supply The test gas supply can be started automatically by means of the gas module’s
solenoid valves or via external solenoid valves.
Depending on the gas supply circuit and the number of analyzer modules installed
there are several test gas layout possibilities (see “Test Gas Supply Control for
Automatic Calibration” section, page 8-A-6).
Test Gas Dew Point The test gas dew point must be nearly identical to the sample gas dew point.
Analyzer Modules
with Multiple
Detectors
In analyzer modules with several detectors (e.g. the Uras26) all detectors are
calibrated simultaneously.
Starting Automatic
Calibration
Automatic calibration is started
• At time intervals determined by the internal clock
• By an external control signal
• Manually via the gas analyzer’s display and control unit
Internal Start Normally automatic calibration is started on a time interval basis by the internal
clock.
The cycle time is initialized with the calibration data (see “Calibration Data for
Automatic Calibration” section, page 8-B-3).
External Start The “Start automatic calibration” control signal is needed for external starting of
automatic calibration:
Level Low (0–3 V) → High (12–24 V) edge. The Low → High transition may also
be generated by an external contact. After the transition the High level
must be present for at least 1 second.
Input Digital input DI1 on Digital I/O Module – “Status signals/ Externally
controlled calibration” standard function block application
Manual Start Automatic calibration can be started manually on the display and control unit. It is
effected
• Only as zero calibration or
• Only as span calibration (see also “Calibration Data for Automatic Calibration”
section, page 8-B-4) or
• As a common zero and span calibration.
Manual start of the automatic calibration of an analyzer module is described on
page 8-D-2.
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