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new tube, inserting the new tube into the probe
handle, and finally replacing and re-tightening the
hex-nut.
Note: The sample probe must be checked for
leakage (as discussed in Section 2.4.1.)
whenever filters or probe tubes are exchanged
or replaced before it is returned to service.
2.5
Biosystems EEPROM equipped
“Smart Sensors”
Each sensor installed in a PhD Ultra detector is
equipped with its own non-volatile memory storage
device or “EEPROM”. The contents of the sensor’s
memory device are designed to be read and
updated directly by the PhD Ultra. The fact that
each sensor is capable of remembering and
communicating important information about itself to
the instrument allows for a number of important PhD
Ultra operating benefits.
2.5.1 Identification of type of sensor by
instrument
Any sensor installed in the PhD Ultra automatically
identifies itself to the instrument microprocessor.
The PhD Ultra automatically recognizes the sensors
installed, displays the sensor on the liquid crystal
display (LCD) and assigns the correct alarm
settings.
2.5.2 Other information stored with the
sensor EEPROM
Besides being identified by type of sensor, recorded
sensor information also includes the sensor serial
number, the most recent calibration settings,
temperature compensation curves, and the most
recent alarm settings. The PhD Ultra automatically
updates all of this data for the sensors currently
installed whenever the instrument is turned on,
whenever a change is made during operation, and
whenever the instrument is turned off.
If a sensor is changed or replaced the PhD Ultra
notes that a change has occurred, displays a “Needs
Cal” message the next time the instrument is turned
back on, and identifies the affected sensors. Even if
the change is only to replace one sensor with
another of the same kind, the PhD Ultra will still
note the change in serial numbers of the sensors
installed, and display the “Needs Cal” message.
The accuracy of sensors
identified as “Needing Calibration” must be
verified by exposure to known concentration
calibration gas before the PhD Ultra is put back
into service. Failure to do so may result in
inaccurate and potentially dangerous readings.
2.5.3 Sensor
replacement
Sensor replacement procedures are covered in
detail in section 5.1.
2.5.4 Missing
sensor
The PhD Ultra is able to determine if a sensor is
removed or becomes disconnected while the
instrument is in normal operation. Removal of a
sensor while the instrument is turned on will trigger a
“Missing Sensor” display message, and cause the
audible and visual alarms for the affected sensor
channel to be activated.
2.5.5 “Can’t ID sensor”
If the PhD Ultra is unable to read the EEPROM of a
smart sensor currently installed, or if a smart sensor
is removed while the instrument is turned off without
being replaced with another sensor, a “Can’t ID
Sensor” message will be displayed, and the affected
sensor channel, (for instance, “Toxic 1”) will be
identified.
Press the mode button to acknowledge the
condition, and allows the use of the instrument for
those sensors that can be successfully read by the
instrument.
