Symptom - Excessive Noise; Symptom - Elevated Baseline; Symptom - Baseline Drift; Symptom - Spikes - ABB PGC5000 Service Instruction

3.4 Symptom – Excessive Noise
Possible Cause
Bad electrical connections
Air Leak
Insufficient clearance for
the plasma electrode
3.5 Symptom – Elevated baseline
Possible Cause
Poor carrier gas
Air Leak
3.6 Symptom – Baseline drift
Possible Cause
Poor pressure control
Column bleed
Plasma cell leak
Contamination or late-
eluting peaks
3.7 Symptom – Spikes
Possible Cause
Loose connections
Missing ground leads
Action(s)
Check the signal cable connection and the bias voltage cable
connection.
Check the signal cable shield for fit. The fitting should be snug.
Verify connection between ground rod and ground.
Leak-check all of the fittings within the oven system to verify a leak-
free system.
The plasma O-ring on the plasma tube is designed to prevent this
issue. If the plasma electrode appears to be too close to the
Swagelok ® fitting, remove power from the analyzer and remove the
plasma tube from the top nut.
Install or replace the plasma O-ring on the plasma tube and re-install
the plasma tube.
Action(s)
Background signal is directly linked to the quality of gases being used.
UHP (ultra-high purity) gases should always be used. If gas quality is
suspected, replace gas with new UHP quality gas.
When UHP gases cannot be used, a scrubber will need to be installed
to remove excess levels of oxygen, water, and trace hydrocarbons.
An air leak in the chromatographic system can also cause an elevated
baseline. Verify that there are no air leaks in the chromatographic
system.
Action(s)
Pressure controls not providing a consistent, pulse free, flow rate to
the detector can cause detector drift.
Monitor the pressure gauges on the supply cylinder and measure the
flow out of the exhaust port over a one-hour time period to insure
correct flow conditions.
Re-condition or replace the column.
Initially, this may appear as column bleed, but the signal will
equilibrate as the oven reaches an isothermal temperature.
Reset the plasma cell in the Swagelok
It is possible that there is a late-eluting peak or contamination that is
coming off the column several runs after it was introduced.
Alter the cycle time of the injection to see is the baseline drift changes
location.
If this is confirmed, install filters to eliminate the contamination.
Extend the instrument cycle time to elute the material prior to the
next analysis.
Action(s)
Verify that the signal cable is securely attached to the electrometer
and the BNC fitting on the collector shield.
Verify that the ground lead from the plasma center electrode is
connected. If it is not, power the analyzer down and re-connect the
center electrode ground lead.
Verify that the main power supply ground lead is connected to the
appropriate oven chassis ground point.
® fitting and tighten to leak-free.
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