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Jun 2001
Before Servicing the Instrument
Agilent 6890 Gas Chromatograph Service Manual
130 Calibration Notes
Calibrating the 6890 GC
Press the [Options] key on the GC keypad and select the Calibration option
to access a list of the 6890 Series GC parameters that can be calibrated.
Calibration options
The following GC parameters can be calibrated:
• The GC oven temperature can be corrected to actual measured
temperature.
• We do not recommend field calibration of flows and pressures, other than
zeroing. A full calibration requires establishing flows and pressures that
are comparable in accuracy to the NIST-traceable factory equipment.
• Flow sensors can be zeroed. The Autoflowzero function, when turned
on, automatically zeroes flow after each run. To use this feature, select
Calibration on the OPTIONS menu, then choose either Front inlet or
Back inlet, and turn Auto flow zero on. After the end of a run, Auto
flow zero shuts down the flow of gases to an inlet, waits for the flow to
drop to zero, measures and stores the flow sensor output, and turns the
gas back on. This takes about two seconds. The zero offset is used to
correct future flow measurements.
• Pressure sensors can be zeroed by fully depressurizing the system, inlets
or detectors. Open appropriate fittings to ensure that there is no residual
or trapped pressure, then select Pressure Zeroing and press the On
key.
• Capillary columns can be calibrated. Length and internal diameter can
be estimated using data from an isothermal run. This is useful when such
data were not provided with the column or if trimming has reduced the
length of the column.
• Additional information regarding each individual inlet, detector, make–
up gas or Aux Pressure/Flow Calibration Ranges can be obtained by
scrolling to the task and pressing the Info key. Typically a calibrated
flow of greater than 50% of the EPC module’s flow range is required to
calibrate. A pressure greater than 70% of an EPC pressure range is
required to calibrate it.
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