OXY5500 Gas Analyzer Operating Instructions
Endress+Hauser 35
Forced Zero Settings
Negative Oxygen Value
Display
Alarm Signal “Forced Zero is
Active”
Forced Zero Active After
Reset
Passive yes no no
Active no no no
Active with alarm no yes no
Active stored no no yes
Active with alarm stored no yes yes
Table 10. Forced zero modes
5.11.3 Forced Zero mode definitions
• Passive mode: Forced zero option is inactivated and negative measurement readings are shown.
• Active mode: In this mode, a negative value will be seen as 0% [ppm] O2. After rebooting the device, the default
mode “passive” is reactivated.
• Active alarm: In this mode, a negative value will be seen as 0% [ppm] O2. An alarm signal “Forced Zero is
active” is displayed at the top of the window. Refer to Figure 40. After rebooting the device, the default mode
“passive” is reactivated.
• Active stored: In this mode, a negative value will be seen as 0% [ppm] O2. No alarm signal is displayed when the
oxygen concentration reading is negative. After rebooting the device, this mode remains active.
• Active with alarm stored: In this mode, a negative value will be seen as a 0% [ppm] O2. This mode combines
the functionality of modes “active alarm” and “active stored”. After rebooting this device, this mode remains
active.
Figure 40. Forced Zero alarm signal
The OXY5500 requires regular calibration as discussed in Calibrating the analyzer → . Negative oxygen values
which may be due to an inaccurate calibration are not displayed when Forced Zero is active.
Once the Forced Zero feature is active, the reading as described above applies to the main measurement screen
and to the analog 4-20 mA output. Negative oxygen values are output as 4 mA.
Alarm Signal
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