Double Sampling - ABB PGC2000 Operation And Service Manual

5. Baseline offset extreme. See "Baseline or Signal Offset (TCD)" or "Baseline or Signal Offset
(FID)."
6. Column broken or connection in the column train disconnected. Perform Test Procedure 7
(Column Train Problems).
7. TCD Failure. Perform Test Procedure 5 (TC Detector Balance) and Test Procedure 6 (Filament
TCD Test), as applicable.
8. FID Failure. Perform Test Procedure 17 (Verification FID Flame Is Ignited) and Test Procedure
15 (FID Reduced Sensitivity), as applicable.
9. FPD Failure. Perform Test Procedure 43 (FPD Gain Setting).
10. Low Zone Temperatures. See "TEMPERATURE CONTROL HARDWARE PROBLEMS" and
Test Procedures 21 through 27.
11. Active stream is stream 9 (no inject occurs on stream 9). Change to correct active stream.
12. Check Method Table for correct entries. Perform Test Procedure 33 (Checking Method Table
Configuration).
13. Sample Valve Failure. Perform Test Procedure 1 (Carrier, Makeup, and Utility Gas Supplies)
and Test Procedure 2 (Carrier and Makeup Gas Flow Adjustments), as applicable. Also see
"Baseline or Signal Offset (TCD)" and "Baseline or Signal Offset (FID)." Repair sample valve
(see "SAMPLE VALVE REPAIR" in Section 8). Check for correct stem volume and length.
14. Actuation solenoid valve vent is plugged or obstructed. Check and remove any obstruction.
15. Solenoid not moving. Replace solenoid valve, driver card, or Chroma I/O board.

Double Sampling

Symptom: The chromatogram peaks appear to have double apexes (see Figure 6-9). The trailing
peak apex is generally smaller than the leading due to the first having the greater sample size.
Cause: Double sampling problems are isolated to the sample valve. Generally the first injection
occurs when the valve is turned on (valve stem inserted into the injection chamber). The second
injection is made when the valve is turned off (the valve stem is withdrawn from the injection
chamber). Perform Test Procedure 19 (Double Sampling).
2000-OSM, F1
TIME
NORMAL
Figure 6-9. DOUBLE SAMPLING
TIME
DOUBLE SAMPLING
6-7