Instruction manual

31
Wait at least 3 minutes after
turning the instrument on to allow sensor
readings to stabilize fully before initiating any
calibration procedures. Failure to wait three
minutes before initiating calibration procedures
may lead to inaccurate and potentially
dangerous readings. If a sensor has just been
replaced, the stabilization period may be longer
(see the chart in section 5.1).
(3) Slide the belt clip towards the rear of the
instrument exposing the four buttons on the
instrument keypad.
(4) Verify that the instrument is in the Basic or
Technician operating mode. To change
operating modes simultaneously hold down the
"+" and"-" keys.
Each time that the operating mode is changed,
the LCD screen will briefly indicate the current
operating mode.
(5) Make sure the instrument is located in an area
where the air is known to be fresh.
(6) Press the keypad button marked "Cal". The
fresh air calibration message will appear briefly
on the instrument LCD.
(7) The fresh air calibration message will be
followed by the zero-adjustment screen.
(8) Press "Cal" to automatically zero the instrument.
An information screen will be briefly displayed
while the adjustments are being made, and
another when the adjustments have been
completed.
(9) Pressing the mode button causes the calibration
values in the memory to remain unchanged
from the last time a fresh air adjustment was
made. An information screen will be displayed
briefly which verifies that the zero values have
not been changed.
(10) After completion of the zero adjustment the
PhD Ultra will automatically return to the gas
reading screen display.
3.5.2 Span calibration using keypad
buttons
Span calibration procedures using buttons on the
instrument keypad are most useful when calibration
of only a single sensor is desired. Span calibration
using the keypad buttons may only be done while in
the Basic or Technician operating mode.
(1) Turn the instrument on.
(2) Slide the belt clip towards the rear of the
instrument exposing the four buttons on the
instrument keypad.
(3) Verify that the instrument is in the Basic or
Technician operating mode. To change
operating modes simultaneously hold down the
"+" and"-" keys.
Each time that the operating mode is changed,
the LCD screen will briefly indicate the current
operating mode.
(4) Turn the instrument off by pressing the mode
button for three full seconds until the "release
button" message appears in the screen.
(5) With the unit turned off, press and hold down
the "Cal" button.
(6) While holding down the "Cal" button, press the
mode button to turn the PhD Ultra back on. The
“Span Calibration” message will appear briefly
on the screen. This message is followed by a
screen showing the message “Cal = Span”.
(7) Press the keypad button marked “Cal” to make
a span adjustment. A screen will briefly display
the message “Span Calibration; Mode =
Cancel”.
Press the mode button at any time to cancel the
calibration mode.
The “Span Calibration” screen will be followed
by another showing the first sensor to be
adjusted.
(8) Attach the cylinder of calibration gas, regulator,
short section of tubing and calibration adapter to
the PhD Ultra as shown in Figure 3.4.2.
Make sure the regulator,
cylinder seating surfaces and threads are clean
and dry before attaching the regulator to the
cylinder of gas. Introduction of contaminants
through the regulator fittings may alter or
degrade the concentration of the gas contained
in the cylinder and may lead to inaccurate and
potentially dangerous gas readings.