Thermo Scientific EASY-nLC 1200 Troubleshooting And Maintenance Manual page 169

Weak or Absent Signal—Leak Upstream of Flow Sensor B
Thermo Scientific
Figure 125 shows a typical pump B profile for a system with a leak upstream of flow sensor B.
Flow sensor B displays a negative flow during the column equilibration and sample loading
steps.
If the gradient is short, a leak upstream of flow sensor B will cause a complete lack of signal
because solvent B is not reaching the columns within the duration of the gradient.
Figure 125. Typical pump B profile for a leak upstream of flow sensor B
Negative flow during the
column equilibration and
sample loading steps
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