RKI Instruments SM-2003U - Manual (Page 19)

Hardware Setup • 19
that calibration gas is applied during a bump test, the shorter the bump
test time, the larger bump test tolerance used to determine whether a
bump test failed or passed. The MODE switch sets the value of the
following bump test parameters:
• Air Purge Time
This is the length of time that a calibration station will draw air
through the AIR fitting on the back of the station to an instrument
installed in it. Air is drawn during a bump test or calibration before an
air adjust operation and to purge calibration gas from the system
after calibration gas has been drawn through the CAL GAS fitting on
the back of the station. This parameter is fixed at 30 seconds for all
switch settings
• Gas Exposure Time
This is the length of time that a calibration station will draw
calibration gas through the CAL GAS fitting on the back of the station
during a bump test or calibration.
• Bump Test Tolerance
The bump test tolerance determines how close the instrument gas
reading must be to the calibration gas concentration for each
channel during a bump test in order to pass the bump test. It is
defined as a percentage of the calibration gas concentration.The
amount that the instrument gas reading differs from the calibration
gas concentration must be equal to or less than this percentage of
the calibration gas concentration. For example, if the tolerance is set
to 50%, and the %LEL calibration gas concentration is 50% LEL,
then the bump test gas reading for the LEL channel on the
instrument must be 50 %LEL ± 25 %LEL.
• Automatic Calibration
This parameter is set to on or off. If it is set to on, then the calibration
station will automatically perform a calibration if a bump test fails.