Servomex NanoTrace DF-760E, Инструкция по эксплуатации

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78 DF-760E User Interface
If, when this screen is entered, and the
Scheduled AutoZero
is turned off, the box in the
upper right corner will not be displayed. When the
Scheduled AutoZero
is switched from
off to on, the box will appear and the time of the
Next
scheduled
AutoZero
will be set to
the current time and date. If no other changes are made, when this screen is accepted the
autozero process will start immediately. Use the
Esc
key to escape from the screen without
starting an autozero process.
Setting a time and date for the next autozero is accomplished by accepting the current time
and date or using the
Next
key to move to the
Next AutoZero
box. With the left and right
arrow keys, move the cursor to the right of the digit you want to change and use the up and
down arrow keys set it to the desired value. When done, use the
Enter
key to move to the
next box.
NOTE: If the
Scheduled AutoZero
is then turned off, the autozero process is stopped and
returning to this screen will not show the
Next AutoZero
box in the upper right hand
corner.
The
AutoZero Interval
can be used to set the frequency of zeroing the oxygen cell starting
with the setting in the box labeled Next AutoZero. The date and time of the next scheduled
AutoZero is automatically calculated based on the current AutoZero Interval setting.
With the
AutoZero Timeout
the user can set the allowed time for stabilization. If the
required stable period is not achieved during this time, the AutoZero is automatically
aborted and the Fail Zero flag is set in the Zero Cal Log as shown in Figure 89.
The system provides warning of a scheduled AutoZero before the calibration takes place,
per the time set in the
Pre-Zero Warning
.
The
Zero Acceptance Criterion
allows the user to select the stability criteria required
before the zero value is accepted. The Stable selection ensures the most accurate zero
calibration but takes the longest time to execute (68 minute delay before the zero process
begins). The Quick selection takes the least time (17 minute delay) and as a result is the
least precise. The Normal selection (recommended) applies an average of the two (34
minute delay).
A relay is available on the Oxygen Analog Output Setup Screen (see page 98) to signal
that a zero calibration is taking place Also, the analog output signal can either be frozen or
allowed to update during the calibration process.
7.6.2.3 Span GSF
As with moisture, GSF (gas scale factor) allows correction of reported ppb for different
background gases. In the case of the oxygen sensor, it is used to correct for changes in the
rate of oxygen diffusion when background gases other than nitrogen are present in the span
calibration gas.
The GSF in oxygen measurements is far less critical than for moisture measurements. In
many applications, the sample GSF does not need to be altered from the default value of
1.00. However, if the sample gas has a significantly different diffusivity compared with
nitrogen (e.g., helium and hydrogen), the GSF should be applied.
The O2 GSF may be calculated or entered directly. It is advisable that the entry be
calculated for any gas listed on the screen.