User guide

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Advanced User Guide 61
Pressure sensors. Disconnect the gas supply line at the back
of the GC. Turning it off is not adequate; the valve may leak.
4 Press [On/Yes] to zero or [Clear] to cancel.
To zero all pressure sensors in all modules
1 Press [Service Mode], scroll to Diagnostics, and press [Enter].
2 Scroll to Electronics and press [Enter].
3 Scroll to Pneumatics and press [Enter].
4 Scroll to Zero all pressure sensors and press [Info]. The GC will
remind you that all gas supplies must be disconnected at the
back panel. Turning them off is not adequate; the valves may
leak.
5 Press [On/Yes] to zero or [Clear] to cancel.
Column calibration
As you use a capillary column, you may occasionally trim off
portions, changing the column length. If measuring the actual
length is impractical, and if you are using EPC with a defined
column, you can use an internal calibration routine to estimate
the actual column length. Similarly, if you do not know the
column internal diameter or believe it is inaccurate, you can
estimate the diameter from related measurements.
Before you can calibrate the column, make sure that:
• You are using a capillary column
• The column is defined
• There are no oven ramps
• The column gas source (usually the inlet) is On and non- zero
Also note that column calibration fails if the calculated column
length correction is >
5 m, or if the calculated diameter
correction is >
20 μm.
Calibration modes
There are three ways to calibrate the column length and/or
diameter:
• Calibrate using an actual measured column flow rate
• Calibrate using an unretained peak time (elution time)
• Calibrate both length and diameter using flow rate and
elution time