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3.4.1 Fresh air "zero" auto-calibration
sequence
The fresh air zero procedure may only be
done while the instrument is being operated
in the
Technician
operating mode.
(1) Turn the instrument on and make sure
gas readings are given in numbers.
If readings are given in the form of “OK”
text messages the instrument is currently
being operated in the “Text Only” mode.
It will be necessary to change to the
Technician
operating mode. Switch
modes (if necessary) by simultaneously
holding down the "+" and"-" key as
discussed in section 2.2.3. Each time
the operating mode is changed, the LCD
screen will briefly indicate the current
operating mode.
(2) Wait at least three minutes after turning
the instrument on to allow sensor
readings to stabilize fully before initiating
auto-calibration procedures.
(3) Make sure the instrument is located in an
area where the air is known to be fresh.
(4) Press the MODE button 3 times within
two seconds. This will "wake up" the
instrument from normal operation, and
put it into the “Auto-Calibration” mode.
A screen will briefly display the message
“ZERO MODE”.
Z E R O
↑↓
M O D E
(5) Pressing the MODE button within five
seconds causes the fresh air adjustment
to be made. (If the MODE button is not
pushed within 5 seconds, the instrument
will return to normal operation.)
The screen will show the message
“WAIT ZERO” while the adjustment is
being completed.
W A I T
↑↓
Z E R O
(6) After successful completion of the “zero”
calibration, the display will prompt you
with the message “SPAN MODE” to
continue with a span calibration
adjustment.
3.4.1.1
Reading “Too High” or “Too
Low” for zero adjust
To reduce the chances of the Ex Chek being
inadvertently zeroed in contaminated air,
only small adjustments are allowed through
the use of the “One Button” auto-zero
sequence. If the necessary adjustments are
too large the display will indicate that the
reading is too low or too high for zero
adjustment. In this case the instrument must
be fresh air zeroed using the “Cal” button on
the instrument keypad and procedures
discussed in Section 3.5.1
of this manual.
Once the instrument has been successfully
zeroed using the “Cal” button, subsequent
calibration adjustments may be made using
the MODE button and “One Button Auto Cal”
logic discussed in this section.
3.4.2 “Span” calibration sequence
After successful completion of the “zero”
auto-calibration adjustment the display will
show the message “SPAN MODE”.
S P A N
↑↓
M O D E
If the MODE button is not pushed within five
seconds a span calibration adjustment will
not be made, and the instrument will be
returned to normal operation.
(1) Press the MODE button within 5 seconds
to initiate “span” auto-calibration. A
screen will ask you to “FLOW GAS”.
The instrument will continue to display
this screen until it determines that
calibration gas has been applied.
