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4.
Disconnect the probe from the gas and let the instrument run briefly in clean air to
purge residual gas. Monitor the purging by placing the selector switch on the GAS
scale. When the reading on this scale returns to zero, the instrument is ready for
use.
Note that while the probe is being connected to a source of methane or system gas, "bloc"
may appear briefly on the display, for example, if some time elapses between connection to the
gas outlet and opening of a valve that allows calibration gas to flow. This will not interfere with
proper calibration.
Error Codes during Automatic Calibration. The only special error code that may
appear during automatic calibration is "nogo" (no go). This code, which denotes that automatic
calibration cannot proceed, may appear in the following circumstances:
i).
More than 30 seconds elapse between the "go" display and the introduction of
calibration gas. If this is the case, wait for an additional period up to 60 seconds,
with gas flowing through the instrument. The "nogo" display will be replaced by
"CAL" when the sensors are calibrated.
ii)
A sensor is outside the normal range for automatic calibration. If this is the case,
the "nogo" display will alternate with a display indicative of the sensor which
cannot be calibrated. Thus, "nogo" alternating with "GAS 2" indicates that the
catalytic combustion sensor is outside the range for automatic calibration.
Similarly, "nogo" alternating with "CO" indicates that the CO sensor is outside the
range for automatic calibration. If this result is obtained, the detector must be
calibrated manually.
iii)
A sensor is not sufficiently stable for calibration to proceed normally or the gas
composition is varying with time. This last condition may hold if the calibration
system has not been purged (e.g., first calibration of the day). If this is the case,
wait for an additional period of up to 60 seconds with gas flowing through the
instrument. If response is stable, the detector will be calibrated and "CAL" will
appear on the display. If the instability persists, the "nogo" display will persist. The
instrument must then be tested manually and the cause of the malfunction corrected.
CAUTION:
Do not use a calibration gas other than Bascom-Turner's calibration gas (Part
No. MC-105) and pure methane or system gas for automatic calibration. If
some calibration gas other than those stipulated here is to be used, calibration
should be carried out manually as described in the Service Manual.
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