14 Instruction Guide
Replacing the NPD Bead
Turning On the Bead
Now that the bead is installed, it is turned off but warm, with
gases sweeping any evaporating moisture off of the bead and
out of the detector. Next you will adjust the bead voltage to
achieve the desired response using either the Adjust Offset
process (recommended for the 7890A GC with firmware A.01.09
or greater) or manually.
Set the Initial Bead Voltage to a Safe Value
Before you turn on the bead for the first time, manually set its
voltage to a safe value so that the new bead is not destroyed.
1 Make sure Adjust Offset is turned Off.
2 After the temperature stabilizes at setpoint, set the initial
Bead Voltage, depending on bead type:
• Blos bead: 0.0 V to 0.5 V
• Ceramic bead (white or black): 0.0 V to 2.0 V
To Use the Adjust Offset Process to Set Bead Voltage
If you choose to use the GC Adjust Offset process, do the
following:
1 Set the offset.
• Blos bead: 20 pA
• Ceramic bead (white or black): 30 pA
2 If your GC has an Equilibration time, set it to 0.0.
3 If using an Agilent data system, start the online session for
the instrument.
For 7890A users: If you changed the bead type, you will need
to resolve the current method to match the new bead type.
4 When the GC becomes Ready, start Adjust Offset.
NPD Bead Replacement.book Page 14 Monday, October 13, 2008 2:32 PM
To Next Page
Loading...
Need help?
General
