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M300EU M300EU OPERATING INSTRUCTIONS
(Addendum to M300EU Manual - P/N 04145)
6.2.1. AUTO-REFERENCE MODE (AREF)
One of the most significant differences between the M300E/EM and the M300EU analyzers is the auto-reference
measurement feature. In this mode, the analyzer makes special measurements and calculations that are
applied to the CO concentration calculation to dramatically improve interferent rejection as well as compensate t
for changes in ambient temperature of the sample gas and age related drift of the optical bench components
(see Section 10.1.1 for detailed information about how and when this A-REF feature occurs).
When in A-REF mode, the analyzer:
• Freezes the CO concentration reading displayed on the front panel and output via the analog outputs or
COM Ports.
• Displays the Message AUTO-REF in the mode filed of the analyzer’s front panel.
• Sets the A-REF status output (pin-7 on the status output connector) to high.
Mode Field
AUTO-REF RANGE = 50.000 PPM CO =12.430
<TST TST> CAL CALZ CALS SETUP
Figure 6-1: Typical Front Panel Display during A-REF Mode
NOTE:
Initiating a calibration through either the keyboard, the COMM ports or digital control inputs terminates
the A-REF mode.
Also, when the instrument is in calibration mode, the A-REF mode is suppressed until the instrument
exits calibration mode.
See Section 6.4 for information about changing the A-REF cycle time or manually initiating an auto-reference
measurement.
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