Oxigraf O2iM NEMA 4X Oxygen Analyzer
February 13, 2007 08-0427-B0, Manual, O2iM.doc Page 21
5.15 O2 Alarm Thresholds
The O2 Alarm Threshold parameter set consists of two pairs of high and low oxygen alarm
thresholds. Alarm A will be asserted for an oxygen concentration less than the Low A threshold or
greater than the High A threshold. Similarly, Alarm B will be asserted for an oxygen concentration
less than the Low B threshold or greater than the High B threshold. The O2 Hysteresis parameter
prevents oscillation of the alarm output due to noise in the oxygen reading. For the high limit
detectors, the thresholds are decreased by the hysteresis value when the oxygen level exceeds the
threshold. This has the effect of requiring the oxygen level to decrease by the hysteresis value in
order to turn the limit detector back off. Similarly, the low limit threshold is increased when the
oxygen level goes below the threshold.
5.16 Low Flow Alarm Threshold
The low flow alarm threshold sets the flow rate limit for the low flow alarm in ml/min.
5.17 Pump Drive Alarm Threshold
The pump drive alarm threshold sets the high pump drive alarm limit in percent drive level.
5.18 Pressure Alarm Thresholds
The high and low-pressure thresholds set the pressure limits for the cell pressure alarm.
5.19 Relay Latch Mode
Limit detectors A and B can be set to latching mode using this setup parameter. In latch mode the
limit detector will remain active even when the activation condition (high or low O2) is removed.
The latch is cleared by pressing the ENTER key. If the activation condition (high or low O2) is still
present then the latch will not be reset
5.20 Relay Flash Mode
Limit detectors A and B can be set to flash when activated at 0.85 Hz and 0.45 Hz, respectively,
using this setup parameter.
5.21 Relay Failsafe Mode
This parameter (if set to "On") enables the relay failsafe mode. For the standard relay allocation
failsafe mode inverts the drive to the WARNING, LIMIT A, and LIMIT B relays, which causes them
to deactivate on an alarm/warning condition. The SYS OK relay is not affected because it is already
in failsafe mode. For the channel relay allocation all four relays, corresponding to channels 0 - 3, are
logically inverted by the failsafe mode option.
In failsafe mode a warning condition will also turn off the level detector or channel alarm relays
independent of the level detector outputs.
5.22 Relay Exclusive Mode
Relay exclusive mode, enabled by this parameter, allows activation of only the highest priority alarm
or status relay. This mode is intended for driving a remote four-light indicator where it is necessary
to have only one light illuminated at a time. The priority ranking, from low to high, is SYS OK,
WARNING, LIMIT B, and LIMIT A.
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