Diagnostic:
Gradient step-test
This is a variation on
the dwell volume measurement. Instead of running a
linear gradient, "stairstep" the composition (e.g., 0% for 5 minutes,
10% for 5 minutes, 20% for 5 minutes, etc.).
If the
absorbance shift at each step is "identical" (i.e., the variations
are within the manufacturer's specification), then the proportioning
system is functioning correctly.
If the
variation is absorbance is greater than that specified for the
proportioning system, the system should be serviced. Proportioning
problems can result from sticking or defective switching valves,
sticking, dirty, or defective check valves, air bubbles in check valves
or pump heads, or software errors.
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2006 LC Resources, Inc. all rights reserved