ENMET ISA-44-RALE-OD - Manual (Page 29)

ISA-44RALE-OD/ISA-44RAHE-OD/ISA-44E-OD ENMET Corporation
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7.0 Replacement Procedures 7.0 Replacement Procedures
7.1 Sensor Replacement ISA-44RALE-OD
The sensors require replacement whenever the specified voltages cannot be obtained or when calibration fails. Whenever
a sensor is replaced, the corresponding ISA-44RALE-OD channel must be recalibrated.
N OTE : If the MOS sensor is replaced, a whole new MOS sensor assembly must be obtained, for the MOS sensor is
permanently cemented into the MOS sensor assembly.
N OTE : One indication that the oxygen cell has depleted is an increasingly frequent need for oxygen gain adjustment as
described in section 6.0 calibration. When installing a new oxygen sensor you must trim the pins.
The oxygen cell must be replaced whenever the oxygen meter cannot be set to 20.9% oxygen using the oxygen gain
potentiometer while the oxygen cell is exposed to clean air. As the cell nears the end of its life, it becomes depleted more
and more quickly until the oxygen channel is constantly in alarm condition. Such an alarm cannot be defeated even if the
oxygen gain is adjusted. In addition, if the oxygen cell is removed from the circuit, the meter immediately falls to the
bottom of the scale and the oxygen alarm activates.
MATERIALS:
q
wire cutter
q
wrench
q
flat headed screwdriver
q
sensing element replacement
(MOS sensor assembly, ENMET part no. 03037-109; oxygen cell part no. 67013-008).
C AUTION : Keep the oxygen cell in its package until approximately 4 hours before installation, when it should be removed
from its package and allowed to adjust to the environment for 4 hours, record the cell serial number for warranty
reference.
PROCEDURE:
1. Turn off the power for the instrument, and remove the compressed air line from the sample head assembly.
Figure 10: MOS Sensor Assembly, Cut Away View
2. MOS SENSOR:
If terminal enclosure is supplied with unit remove terminal enclosure cover disconnect sensor assembly. Then
unscrew the MOS sensor assembly from the terminal enclosure. Screw the new assembly onto the terminal enclosure
and connect to correct terminals, see table 3 in section 3.0.
If terminal enclosure in not supplied, remove the tubing leading to the oxygen cell housing from the junction between
the sample head assembly and the MOS sensor assembly. Inside the control unit, remove the display plate, and
disconnect the MOS sensor wires from TB1-6, TB1-7 and TB1-8. Then unscrew the MOS sensor assembly from the
conduit junction to the control unit, and pull the assembly and wires out. Feed the wires of the new assembly
through the conduit. the conduit. Connect the wires to TB1-6 (brown), TB1-7 (orange) and TB1-8 (blue). Replace
the tubing leading to the oxygen cell housing.
Outlet for compressed air
MOS Sensor
Cement
Explosionproof
Enclosure
Inlet for compressed air