User guide

Options 3
Advanced User Guide 59
Calibration
Press [Calibration] to list the parameters that can be calibrated.
These include:
• Inlets
• Detectors
• ALS
• Columns
• Oven
• Atmospheric pressure
In general, you will only need to calibrate the EPC modules and
capillary columns. ALS, oven, and atmospheric pressure
calibration should only be performed be trained service
personnel.
The calibration displays are discussed in the Agilent 7890A
Service Manual.
Maintaining EPC calibration—inlets, detectors, PCM, and AUX
The EPC gas control modules contain flow and/or pressure
sensors that are calibrated at the factory. Sensitivity (slope of
the curve) is quite stable, but zero offset requires periodic
updating.
Flow sensors
The split/splitless and purged packed inlet modules use flow
sensors. If the Auto flow zero feature (see page 59) is on, they are
zeroed automatically after each run. This is the recommended
way. They can also be zeroed manually—see “To zero a specific
flow or pressure sensor.
Pressure sensors
All EPC control modules use pressure sensors. They can be
zeroed as a group or individually. There is no automatic zero for
pressure sensors.
Auto flow zero
A useful calibration option is Auto flow zero. When it is On, after
the end of a run the GC shuts down the flow of gases to an inlet,
waits for the flow to drop to zero, measures and stores the flow