GxT Ferret 54 ENGINE DIAGNOSTIC CENTER - Manual (Page 86)

MAINTENANCE
The operations described below are found
under
Gas Detector Service in the Diagnostic
Center section of the Setup menu.
ZERO
The ZERO process draws air through a
separate internal charcoal filter to set the
internal zero levels for HC, CO, CO2 and
NOx, and to adjust the full scale level for O2.
The Gas Detector needs to have the ZERO
references adjusted occasionally to assure
accurate readings.
After the WARM-UP process is complete a
ZERO and a PURGE will be performed. If
the Gas Detector determines that a ZERO
is needed while running a test, a message
will be set (indicated by the flashing ‘
✳ ’ ).
While viewing this message, NEXT can be
pressed to perform the ZEROing process
without leaving the test. If you choose not to
respond, the message marker will stay as a
reminder.
While performing a road test or recording
data it may not be convenient to ZERO
immediately when the message appears. It
is NOT necessary to interrupt a test when a
ZERO message appears.
This selection may be used to verify the
ZERO at any time other than those
conditions described above.
PURGE
The purge process turns on the sample
pump to draw air through the sampling
system. The Sample probe should be placed
where fresh air can be drawn in. At the end
of the purge a message will be set if the gas
values are not close to zero. Exhaust
residues can accumulate in the sample
system, especially if the Diagnostic Center
is turned off immediately after sampling
exhaust. In such a case, several PURGEs
may be necessary to clear the system.
A PURGE is performed automatically at the
end of the WARM-UP period.
8-1
B
E SURE THE VALVE ON THE CALIBRATION
GAS BOTTLE IS
CLOSED!
A
LLOWING
C
ALIBRATION GAS TO FLOW
DURING
ZERO
ING OR SAMPLING MAY
RESULT IN
ERRORS!!