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4.
The detector display will show "GAS 2" while the catalytic combustion sensor is
being re-calibrated and "CO" when the CO sensor is being re-calibrated.
5.
After calibration, the detector will show "CAL" and the instrument will beep briefly.
Remove the probe from the gas outlet. The instrument is ready for use.
Note: When the Gas Dispenser is used, it may be useful to attach the 7" extension (with the
white Teflon tip) to the end of the standard probe. The white Teflon tip is designed to fit
the Gas Dispenser port.
Note: During calibration, the selector switch remains in the AUTO ZERO position. After
calibration is complete and "CAL" is displayed, the selector switch must be placed at
some other scale (or the OFF position) to return the detector to a normal operating mode.
CAUTION:
Automatic calibration presupposes and depends on using Bascom-Turner's
calibration gas (Part No. MC-105). Do not use a different gas for automatic
calibration.
The thermal conductivity sensor is calibrated at the factory with methane. Routine re-
calibration of this sensor is not necessary.
operationally using air as the reference gas every time the AUTO ZERO routine is used.
However, the thermal conductivity sensor should be re-calibrated if it has been re-calibrated by
the user with system gas since the gas composition varies seasonally and sometimes more
frequently.
To calibrate the thermal conductivity sensor, proceed as follows:
1.
Place the selector switch on "AUTO ZERO" and zero the instrument in clean air.
The usual series of displays will appear on the detector display. Note that if the
instrument had just been calibrated with the methane and CO calibration gas, the
selector switch must be moved to some other scale and given 30 seconds to purge
residual gas before the AUTO ZERO routine is repeated.
2.
After "End" appears on the display and the instrument beeps, block the probe tip
manually until "bloc" appears on the display. Now release the block. The display
will show "go" and the instrument is ready for calibration.
3.
Connect the probe to a source of pure methane or system gas. The gas should not
exceed 6" or 7" of water. The display will show "GAS 1" while the thermal
conductivity sensor is being calibrated. When calibration is complete, "CAL" will
appear on the display and the instrument will beep briefly.
A-CAL Calibration with the Methane or System Gas
The thermal conductivity sensor is checked
22
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