To Measure Npd Leakage Current - Agilent Technologies 7890 Series Troubleshooting Manual

8
Troubleshooting Tasks

To Measure NPD Leakage Current

200
1
Load the analytical method.
Set the NPD Adjust Offset to Off and the Bead Voltage to 0.00 V.
2
• Leave the NPD at operating temperature.
• Leave flows on or off.
Press [Front Det] or [Back Det], then scroll to Output.
3
4
Verify that the output (leakage current) is stable and
< 1.0 pA.
5
The output should slowly drop toward 0.0 pA, and should
stabilize in the tenths of a picoamp. Current > 2.0pA
indicates a problem.
If the current is > 2.0pA, do the following:
• Inspect the jet for contamination.
• Check the column or column adapter fitting for leaks.
• Ensure that the metal sealing ring is not crushed or
misaligned. See To Maintain the NPD Collector, Ceramic
Insulators, and Jet
Agilent 7890 Series Troubleshooting