Servomex DF-310E, Руководство оператора

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User Interface DF-310E 87
following procedure can be followed: purge the sensor with gas that is free of O
2
until the output
is stable. A suitable way to obtain an oxygen-free gas is to pass a pure grade of nitrogen gas
through an oxygen purifier such as SAES MicroTorr™, Millipore Waferpure™ or Semigas
Nanochem
®
resin purifiers. It is necessary to have a zero gas sample source that is assured to be
at least one order of magnitude purer than the lowest resolution of the Analyzer.
Note: The difficulty in delivering a high quality zero gas to the Analyzer in the field can
introduce significant error when attempting to zero calibrate the Analyzer. It is recommended
that recalibration be done at the factory with its certified low ppb system. If checking zero
calibration in the field, ensure that the gas system used to zero calibrate the Analyzer is leak-free
by performing the low flow test described on page 97.
Reaching a stable zero for the lowest range Analyzer may require 24 hours or longer, even
assuming that the Analyzer has been running continuously for several weeks on a process
application where readings are near the detection limits of the Analyzer. It is recommended that
a recorder be used to chart the zero point, especially for low trace units. When the Sensor Zero
entry is selected, the display will present Figure 57.
Figure 57: Sensor Zero Menu
8.6.3.2.1 ZERO REF
The ZERO REF value is a numerical indicator for calibration changes made in the field. All
instruments are shipped from the factory with a ZERO REF value of 0.00. The number will
become negative, following a user zero calibration, if the sensor zero is below the factory
calibration and vice versa. This value should be recorded both before and after a Zero
Calibration.
8.6.3.2.2 Reset Orig(inal) Zero
The Reset Orig Zero entry is used to restore the zero calibration that was made at the factory
when the unit was manufactured, or the New Sensor zero calibration if the sensor has been field
replaced.
If the Reset Orig Zero entry is selected, the display will ask Erase?... FOR YES . Press
to use the factory set calibration. The Reset Orig Zero line of Figure 57 will disappear. It is
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