56 DF-745SG
User Interface
H
2
O readings (display and output) to compensate for the long term downward
trending in the readings during cleanup. The Active Zero Offset provides an
automatic addition of offset that occurs in miniscule steps, and within set
guidelines, corresponding to predictable behavior during cleanup.
Figure 57: Active Zero On/Off Menu
When Active Zero Offset is enabled through the Diagnostics Menu, the User Zero
Offset feature is disabled and vice versa. See page 39 for more information on the
User Zero function. While the User Zero Offset feature requires the user to enter a
fixed positive offset value to accommodate the baseline cleanup, the Active Zero
Offset does so automatically, and only when necessary.
The current Active Zero Offset value is shown in the Check/Adjust Zero screen as
shown in Figure 24. It starts at a value of 0.00 ppb when the analyzer is first
turned on, and then increments automatically as the analyzer applies offset to the
readings. After each User Zero Calibration, the Active Zero Offset value is reset to
0.00 ppb and then automatically increments again as needed.
The Active Zero Offset is designed to operate when the zero baseline is falling at a
rate less than 0.1 ppb/hr as would be the case after 1-2 weeks of initial operation.
If user calibrations are performed sooner, the H
2
O readings may be decreasing too
rapidly for the Active Zero Offset feature to operate properly and negative H
2
O
readings may result.
If the Active Zero Offset value reaches 5 ppb a warning message CAL ZERO will
flash in the system status block on the display instructing the user that a zero
calibration should be performed. The maximum amount of offset that can be
applied by this feature is 5 ppb. Any further downward trend (baseline cleanup)
exceeding –0.3ppb will result in negative readings until the next user calibration is
performed resetting the Active Zero Offset value to zero.
If the Active Zero Offset feature is turned off, the User Zero Offset value will
appear in its’ place in the Check/Adjust Zero menu. The previous user Zero Offset
value (if any) will reappear and immediately be applied to the live display readings.
Likewise, if the Active Zero Offset feature is on, then its’ value (if any) will appear
and immediately be applied to the live readings.
Summary of Contents for NanoTrace DF-745SG
Page 1: ...NanoTrace Moisture Analyzer DF 745SG OPERATOR MANUAL ...
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Page 30: ...24 DF 745SG Options ...
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Page 86: ...80 DF 745SG Appendix A User Menu Screens Page 47 Page 49 Page 52 Page 53 Page 55 Page 56 ...
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