BT CGA-411 Operation Manual page 34

3. Remove four screws from the aluminum block manifold freeing the sensor hold-
down plate and cable strap, and lift the methane sensor out of its well. Verify that
an O-ring remains positioned on the shelf at the top of the well.
4. Install the new sensor assembly and press down until it sits in the well with its cable
aligned directly toward the 6 pin connector on the main circuit board. Align the
four holes in the new sensor hold-down plate with the corresponding holes in the
manifold, and insert and tighten the four screws.
5. Reconnect the 6 pin filament connector to the main circuit board with the label on
the connector facing upward. Put the cable clamp around the new cable and secure
the clamp to the manifold with a screw.
Note: If the 6 pin filament connector is inverted, the display will show FAIL when the
instrument is turned on.
6. Replace the top cover on the instrument and move it gently until the post of the
selector switch falls into the slotted switch on the main circuit board. Replace the
two screws holding the top to the bottom half of the case.
II. Adjustment and Calibration of the Methane Sensor
Access the set-up mode by setting the front panel switch to the % Oxygen position,
pressing simultaneously the two push button switches, and turning the front panel switch to the
AUTO ZERO position. The display will show "Pu" followed by a number.
1. Press switch #2 twice. The display will advance to: "
By pressing switch #1 and #2 as described in detail in Section 11, set the number at
the ambient room temperature, in degrees centigrade, within ±0.2
depression of switch #2 will show: "
2. Press switch #2 again. The display will show: "
By pressing switch #1 and #2 as described in detail in Section 11, set the displayed
number to 400.0. The final depression of switch #2 will show: "
400.0.
The displayed number may be ±0.4, i.e., 399.6 to 400.4.
3. Exit the set-up mode and return to a normal operating mode by placing the front
panel switch a position other than AUTO ZERO. Then switch back to AUTO
ZERO, allow the instrument to zero and calibrate the sensor automatically (block
intake after "End" appears on the display and introduce calibration gas after "go" -
see Section 10).
o
C 1" followed by a number.
o
C 1" followed by the room temperature (
o
C 2" followed by a number.
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o
C. The final
o
C).
o
C 2" followed by