Ametek 241CE II User Manual page 57

The instantaneous intensities of light impinging on both phototransistors are
monitored simultaneously. At 0.25 °C intervals, the light-intensity values and
mirror temperatures are stored into memory. After each data set is stored, the
array of temperature and light-intensity values are analyzed to determine if a
persistent increase in light intensity has occurred at either phototransistor. This
signifies condensation on the corresponding mirror surface – hydrocarbon on
the rough surface or water on the smooth surface.
The Cooling Stage termination (End-of-Run Type) has been set for the HCDP
and the Cooling Stage will terminate:
•
•
•
If the Cooling Stage termination is due to the Thermoelectric Cooler being
unable to further reduce the mirror temperature after 2 minutes, the Stage-
Time-Out (w TimeOut) SCode and Cooling-Stage-Time-Out (w Cool TimeOut)
XSCode are generated.
If the HCDP temperature was not determined, the Hydrocarbon-Dewpoint-Tem-
perature-Not-Found (w No HC DP) SCode is generated.
During the Cooling Stage, signal values displayed as asterisks (i.e., '****') on the
User Interface indicate that a new value is being determined. Until a new value
is determined, at the end of the Cooling Stage, the analog output signal is held
constant at the value from the previous measuring cycle. As soon as a new
value is determined, the asterisks ('****') on the User Interface and the previ-
ous value on the analog output channel are replaced by the new HCDP tem-
perature. The SCode message on the User Interface and on the analog output
channel is updated with the sum of all SCodes generated since the end of the
previous stage.
If any of the determined values exceed the associated alarm setpoint, or the
SCode indicates analyzer malfunction (i.e., a Fault or Warning alarm), the
appropriate relays are activated and their corresponding LEDs on the User
Interface are turned On. If the alarm is a Fault Alarm, the alphanumeric display
on the User Interface will also flash. The SCode is determined by the built-in
diagnostics function.
PN 903-8797, Rev A
When the Hydrocarbon Dewpoint temperature is found (factory-set de-
fault),
or
When the Low Mirror Temperature setpoint is reached,
or
If, after 2 minutes, the Thermoelectric Cooler cannot further reduce the
mirror temperature.
Installation and Start-Up
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