30
Figure 3.4.2. PhD Ultra calibration setup
The regulator will automatically begin to flow
calibration gas as soon as it is screwed into the
cylinder of gas. Be sure to use a 1.0 liter/minute
regulator with the PhD Ultra.
(3) When the instrument detects that calibration gas
has reached the sensors, the display will show
the message “Please Wait”.
(4) If the instrument determines that the calibration
gas being used is a multi-component mixture
the display will show the message “Multi Cal
Gas Detected”.
The instrument will then show a succession of
screens as each sensor that can be calibrated
using the multi-component mixture is adjusted
in turn. The entire span adjustment process is
automatic.
(5) As each sensor is adjusted the screen indicates
the concentration and type of test gas that is
being used to calibrate the sensor.
Calibration values shown in
the calibration value table must match those
that appear on the calibration gas cylinder(s)
that will be used to calibrate the PhD Ultra. Non-
matching calibration gas and calibration gas
value settings will lead to inaccurate and
potentially dangerous readings.
Note: If multiple cylinders of calibration gas are
used during calibration, it will be necessary to
change cylinders between span adjustments. In
this case the display will indicate the type and
concentration of the next cylinder of calibration
gas to be applied.
When the instrument has detected that the
proper gas has been applied the sensor will be
adjusted.
(6) When all sensors currently installed have been
successfully span adjusted, the display will
announce “Auto Calibration Completed”. The
instrument will then shut itself off.
(7) Remove all fittings from the PhD Ultra, and
press the mode button to turn the instrument on
and resume normal operation.
Note: It is possible to exit the auto-calibration
mode at any time prior to completion by
pressing and holding down the mode button to
turn the instrument off. The instrument will
retain the updated settings for those sensors
whose span adjustments have been completed.
Sensors that were not successfully adjusted at
the time the auto-calibration sequence was
terminated will trigger a “Needs Cal” message at
the time the instrument is next turned on. The
accuracy of those remaining sensors should be
verified by exposure to known concentration
test gas before the instrument is put back into
service.
3.5
Manual calibration procedure
It is also possible to calibrate the PhD Ultra
manually using the four buttons on the instrument
keypad.
3.5.1 Manual fresh air "zero" through
keypad buttons
Note: The manual fresh air “zero” calibration
procedure bypasses the PhD Ultra’s safeguards
against calibration in a contaminated
atmosphere. Be sure to perform this calibration
in an area where the air is known to be fresh.
(1) Turn the instrument on.
(2) Wait at least three minutes after turning the
instrument on to allow sensor readings to
stabilize fully
before
initiating the fresh air zero
procedure.
