The Pacer Cycle - GE Optica Operator's Manual

1.6 The PACER Cycle

GE Measurement & Control has developed and patented a compensation technique called PACER (Programmable
Automatic Contaminant Error Reduction) that is very effective in reducing the Raoult Effect error associated with
soluble contaminants, particularly for near-ambient dew points. The Optica is equipped with the PACER cycle as well
as AUTO balance as found on earlier models. The user can choose which self-cleaning and balancing routine to run
depending on the severity of contamination.
The PACER cycle, diagrammed in Figure 3 below, begins with a coalescence period, during which the mirror is cooled
well below the dew point of the sample gas, condensing out a large amount of water.
This excess water easily dissolves any water-soluble contaminants. The mirror is then heated. During the heating
phase, the large puddles of water gradually evaporate, carrying increasingly heavy concentrations of salts as the
puddles become smaller. Finally, when all the puddles have evaporated, dry "islands" of crystallized salt are left on the
mirror. The area between the islands (80-85% of the mirror surface) is now clean and shiny, whereas before the PACER
cycle it may have been completely covered. The total amount of contamination has not been reduced, but instead,
redistributed as shown in Figure 4 below, with more clean mirror surface available for dew formation. The reflected
light signal is then electronically balanced against the reference.
Optica™ Operator's Manual
Figure 3: A Typical PACER Cycle
Before
PACER Cycle
Figure 4: Results of the PACER Cycle
Chapter 1. Features and Capabilities
After
PACER Cycle
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