ZIRCONIA OXYGEN PROBE OUTPUT (mV) - Novatech Controls

4.2 ALARM BUTTON
Figure 4.1 Operator's Panel
Repeatedly pressing the operators ‘ALARM’ button will produce alarm displays in sequence on the lower line of
the LCD display. If an alarm has cleared prior to pressing the ‘ALARM’ button, it will not re-appear on a second
run through the alarms. Active alarms which have been previously displayed will have ‘ACC’ (accepted),
displayed alongside. New alarms will not have ‘ACC’ displayed until a second press of the ‘ALARM’ button.
After the last active alarm is indicated, the lower line of the display will return to the last displayed lower line
variable.
The alarm ‘LED’ will flash on alarm. Pressing the ‘ALARM’ button will cause the LED to go steady if any alarms
are still active, or extinguish if there are no active alarms. The horn relay will operate when an alarm occurs.
Pressing ‘ALARM’ will mute the horn relay which will re-initiate on any new alarms.
4.3 ALARM SCHEDULE
4.3.1 SUMMARY OF ALARMS
ALARM DESCRIPTION
‘SENSOR FAIL’ Oxygen cell or electrode failure (high impedance); (inhibited under 650°C).
‘PROBE HEATER In the first 20 minutes of power being applied to
FAILURE’ the heater after being switched on, this alarm will not occur, but a ‘PROBE
UNDER–TEMPERATURE’ display will occur and relay RL8 will be activated.
Refer to Section 6.13.
‘PROBE TC O/C’ Probe thermocouple is open circuit. The heater in heated probes will switch off.
‘REF AIR FAIL’ Low reference air flow to probe.
‘FLOW SWITCH’ The reference air flow switch has failed. This is tested by automatically
switching off the reference air pump once every ten minutes for three seconds to
check the operation of the flow switch.
‘A/D CAL ERROR’ The analog to digital converter has been found to fall outside the normal
calibration specifications. This is an electronic fault.
‘D/A CAL ERROR’ The digital to analog and voltage isolator circuit has been found to fall outside
the normal calibration specifications. This check is only performed when the
‘AUTO CAL’ button is pressed. Refer to Section 6.6.
3.2 NOVATECH OXYGEN ANALYSER