Low Signal; Noisy - ABB PGC5000 Series Service Instructions Manual

PGC5000
PGC5000 Series Service Instructions
reaction gas is connected, there is an air leak, or there is no reaction gas flow. Turn off the power to the plasma and check
the gas supply. Check for leaks and check flow rate.
Signal cable problem: Verify that the collector shield BNC fitting contacts the exhaust tube.
1. Remove the BNC cable from the collector shield.
2. Verify contact between the center pin of the BNC and the exhaust tube, using a volt-ohm-milliammeter (VOM) or
continuity tester.
3. Reconnect the BNC cable to the collector shield.
4. Verify the cable is connected to the collector shield and the electrometer board.
Verify bias voltage: Using a VOM, measure the voltage at the bias rod. The voltage should be 110 volts between the rod and
the oven chassis.

5.10.3 Low signal

No restrictor: The detector is not as sensitive when no restriction is on the exhaust flow. Verify that the restrictor in place is a
0.1 id tube. If you are unsure, replace the restrictor with one of known dimensions.
Low or no bias voltage: Verify the connection of bias voltage to the bias voltage rod. If necessary, verify that bias voltage is
present on the bias voltage rod by connecting a volt-ohm-milliammeter to the bias rod (red lead) and ground (black lead).
The voltage should be at least 110 volts.
Leakage in the chromatographic system: Verify the retention times for the components of interest. If these are correct, check
for leakage on all the fittings on the detector end of the system. If the retention times have shifted, look for leaks on the
valve rod.
Wrong reaction gas: Using nitrogen as the reaction gas will cause low signal. Verify that the proper reaction gas is being used.
Improper restrictor in place: Too large of a restrictor results in poor plasma performance, leading to low sensitivity. Verify that
the proper restrictor is in place, or replace the restrictor with one of know proper dimensions.
High response and shifted retention times: This is a problem that may be caused by a restriction in the exhaust tube. In this
case, the retention times for the analyses will have shifted later in the chromatogram.
1. Visually inspect the exhaust tube to identify any materials that may be plugging the tube.
2. Insert a syringe cleaning wire into the exhaust tube.
If these actions do not resolve the problem, replace the exhaust tube with a new one.

5.10.4 Noisy

Bad electrical connections: Check the signal cable connection and the bias voltage cable connection. Check the signal cable
shield for fit. This fitting should be snug for best performance. Verify the connection between ground and ground.
Leak: Especially true when operating in the helium ionization detection (HID) mode. If the detector is being very noisy, check
all fittings within the oven system for leaks. Verify the installation of or replace the PTFE noise shield in the top nut.
Plasma electrode too close to Swagelok fitting: The plasma O-ring on the plasma tube is meant to prevent this issue. If this
appears to be the case:
1. Turn off the power to the plasma.
2. Remove the plasma shield.
3. Remove the plasma tube from the top nut.
4. Install or replace the plasma O-ring on the plasma tube.
5. Reinstall the plasma tube.
6. Re-attach the plasma shield.
7. Turn on power to the plasma.
SI/PGC5000-EN, Rev B
5 Diagnostics and troubleshooting
34