Igema EWLS, Installation And Operating Instruction

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4.3 Setup
For ensuring high availability IGEMA recommends the use of 2 power supply units
(redundancy). In terms of hardware the CU-3 is designed for operation with 2 power supply
units.
Both the measuring unit (MU-3) and the control unit (CU-3) have 2 independent electronic
circuits with their own processors. All processors carry out regular self-tests for internal faults
in the electronic circuit. This provides self-monitoring of the device and thus a higher safety
standard.
Measuring unit
Both electronic circuits record the state of the probes and send it to the control unit.
Control unit:
Both electronic circuits evaluate the status messages of both electronic circuits of the
measuring unit. If both status messages are identical the required reaction (Chap. 4.2) is
carried out.
A plausibility check takes place.
Each electronic circuit switches its “own” relay (SPDT) for the corresponding output. Only
when both relays of both electronic circuits are driven (activated) equally (e.g. during normal
operating status) is the output active.
The output contacts do not have any latching. The switching behaviour is
exclusively in line with the desired specified (programmed) state. If
latching is required, this manual locking (latching) must be carried out on
site.
4.4 Components of the control unit (CU-3)
The control unit contains:
1 LCD display (2-line each 16 characters) for communication with the operator
(Programming and information display)
4 buttons for programming
3 LEDs as additional status indication
3 SPDT outputs to be freely assigned by customer (see assignment plan Chap.: 5.2.2)
when using two probes
1
4mA.. 20mA output for loads up to 500Ω, not galv. insulated (optional)
Danger