Ametek 888

Alarms | Appendix E-5
Alarm Specics
The twenty-three (23) alarm conditions are detailed in this section. Note
that additional alarms can be added to the system in the future.
Alarm Timer Stopped [1]
The Period timer can be stopped to troubleshoot the analyzer. For exam-
ple, if necessary, the analyzer can be made to continually flush the sample
cell. If the timer were to be active the state machine would continue to
function and return to the Measurement state (Period 4). A Level 2 alarm
occurs as a reminder that the analyzer is not operating normally.
Restarting the timer clears the alarm condition.
Cell Temperature Alarm [2]
There is a temperature sensor mounted on the sample cell in the oven
compartment. The temperature of that cell must be controlled to within
the configured deviation. Typically the target temperature is 150 ± 5 °C.
If the temperature is outside the allowable range, a Level 1 alarm occurs.
This is a potentially serious condition as it could allow sulfur to build up
on the optical surfaces.
The alarm condition will clear itself once the temperature is within range.
If the cell doesn’t reach temperature, there could be a problem with the
heater, over-temperature detection, or excessive gas flow through the
sample system. Note that excessive gas flow can conduct heat from the
oven.
Low Light Alarm [3]
The Model 888 analyzer adjusts light intensity automatically by chang-
ing the number of lamp flashes per second. If the optical surfaces slowly
become fouled, the number of flashes per second is increased to maintain
light intensity on the detectors. Once the flash rate reaches 50, it is no
longer possible to make a concentration measurement every second. This
is a Level 2 alarm condition.
User intervention is required to increase the light intensity at the detec-
tors. Possible corrective actions include cleaning the sample cell windows,
and the mirrors in the reflector block, and to check the lamp operation.