Elgo LIMAX44 RED, Operating Manual

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Design and Functions
9.2 Operating Modes
The sensor can be operated in two different modes:

Safe dual-channel operation

Non-safe single-channel operation (energy saving mode)
Switching between modes happens automatically, depending on the supply voltage.
9.2.1 Dual-Channel Operation
Usually, the sensor works in dual-channel operation. In this mode, both channels are fully functional and deter-
mine the position independently of each other. After determining the position, the position results of the two
channels are compared and then transmitted to the safe evaluation unit via a safe interface. If an internal error
is detected or if the position results of the two channels do not match, the sensor sends a request for transition
into safe state to the evaluation unit. The evaluation unit has to make sure that the safety circuit is opened.
Further information:

Overview of error status and possible errors:

12.6

Protocol description of the safe position information transmission

9.5.4
9.2.2 Single-Channel Operation
In order to keep the door zone indication functioning in case of loss of the regular power supply (24V operating
voltage), the sensor can be operated with an external 12V back-up battery or an emergency power supply. To
maximise the durability of the back-up battery, one channel is switched off. All position comparisons between
the two channels are terminated in such a case and the sensor communicates only the non-safe position result
of one channel to the evaluation unit. If the evaluation unit is still in operation at that time, it can further process
this position information for non safety related functions. The evaluation unit absolutely has to switch into safe
state.
Further information:

Possible additional circuit for automatic switch to single-channel operation

9.5.1

Protocol description of the position information transmission

9.5.4
9.3 LED Signals
The LEDs at the upper side of the sensor (shown in Fig. 22) signal the operating status or possible errors:

PWR A: Supply voltage channel A

PWR B: Supply voltage channel B

RUN: Operating status

ERR: Signalling of an error

TAPE: Magnetic tape status
Fig. 22: LED signals on the upper side of the sensor
The LEDs PWR A, PWR B signal the status in a static manner. They are either turned on or off. The LED RUN
flashes, with the frequency depending on the operating status. The LED ERR has three possible states: Off, regu-
lar flashing and irregular flashing. The LED TAPE also knows three possible states: off, on and irregular flashing.