ENMET ISA-44-RALE-OD - Manual (Page 13)

ISA-44RALE-OD/ISA-44RAHE-OD/ISA-44E-OD ENMET Corporation
9
Sample Head Assembly see figure 2
Feature Description
Sample Head
Assembly This assembly includes an inlet orifice, regulator, air pressure gauge and humidifier.
This assembly pressure regulates and humidifies the compressed air for the sensors.
High-Pressure
Regulator
(ISA-44RAHE-OD only) This device regulates high-pressure air (300 - 5000 PSI) for the sample head assembly.
This device must be used when monitoring very high-pressure air. The high-pressure
regulator is part of the ISA-44RAHE-OD and is not included with ISA-44RALE-OD.
Terminal Enclosure: See figure 3
Terminal Enclosure This enclosure supports the Purge/Operate/Horn-off switch on the outside and houses
all user terminal connections on the inside. The Wiring Table describes these terminal
connections.
MOS Sensor Enclosure This explosion-proof enclosure houses the MOS sensor. Air flows through the sample
head assembly into this enclosure so the MOS sensor can monitor the CO content of the
compressed air.
Oxygen Cell Enclosure This enclosure houses the oxygen cell. Air flows through the sample head assembly
into this enclosure so the oxygen cell can monitor the oxygen content of the compressed
air.
Switch
Purge/Operate/Horn-off This switch is located on the terminal enclosure.
In the PURGE position, this switch increases the MOS sensor heater voltage to clear off
contaminants from the sensor surface and silences horn if supplied.
In the OPERATE position, this switch sets the MOS sensor to normal operation for
monitoring CO and the horn circuit is active if supplied.
The HORN-OFF position is included only on instruments with a factory-installed horn
(option). When in the HORN-OFF position, the switch silences the horn during testing
or calibration procedures.
IMPORTANT: While the switch is set to PURGE, the MOS sensor does not monitor
target gases accurately.
Oxygen Gain Knob Located on the terminal enclosure. This knob is actually a gain potentiometer for the
oxygen channel. It is adjusted periodically during operation and calibration.
Relay contact
connections Located on terminal blocks inside the terminal enclosure. See Wiring Information table
3. All of these relays are non-latching; they change state upon alarm and reset when the
channel comes out of alarm.
The oxygen channel has one set of relay contacts for its one alarm point.
The gas channel has two sets of relay contacts, one for each alarm point (high and low).
Relay contacts are in alarm position when the corresponding channel is in alarm.
Relay contacts are also in alarm position when the power to a channel is interrupted.
Relay contacts automatically reset when the gas or oxygen hazard diminishes beyond
the alarm point.
Audio Alarm
(Horn-Optional) A factory-installed horn activates during certain alarms; see section 4.3. This horn is
optional; it is not included on all ISA-44RALE-OD / ISA-44E-OD instruments.