Other Time-Coded Functions; Auto Zero - ABB PGC2000 Operation And Service Manual

Another method for handling badly tailing peaks is "End=Crest+" (see Figure 4-27). This code forces
the end of the peak to be the crest time plus the time specified in the code, providing a reproducible
end to the peak even if the crest of the peak is moving. To use this command, insert "End = Crest+"
into the method together with a specified time after the crest. The method allows times from 1 to 380
for the length of time after the crest.
Area rejection is used to separate smaller, unwanted, peaks from larger peaks. If several small
peaks are close to peaks of interest, area rejection allows you to define a minimum area a peak has
to reach to be retained. Slope detection still measures all the peaks, but at the end of the analysis all
peaks below the rejection area are disregarded. To use area rejection, insert Reject Area into the
method, together with the threshold area value which tells the controller what minimum peak area is
to be retained for analysis. The method allows you to specify areas from 1.0 to 9,000,000 for the
rejection area (corrected peak area in the Raw Data Report).

OTHER TIME-CODED FUNCTIONS

This section discusses the time-coded functions that are not part of peak detection.
A method table will contain one or more of these functions when the particular application requires it.
The following sections describe each function.

Auto Zero

Auto zero supplies an offset which brings the raw baseline signal down to its most sensitive range. It
also supplies a software offset to bring the signal to 2.0 mV. The auto zero offset is ±100 mV with a
resolution of 1.7 mV. Using all of the offset voltage generates an alarm.
The auto zero function occurs immediately when requested, except that it is ignored during any of the
following situations (which cause alarms):
•
When a noise calculation routine is in progress
•
If a forced gate routine is in progress
•
If a slope detect routine is currently processing a peak
2000-OSM, F1
TIME
END=CREST+
Figure 4-27. EXAMPLE OF END=CREST+
CREST
END SPECIFIED BY
END=CREST+
4-26