Operation
EL2904 31Version: 3.2.2
NOTICE
Route the signal cable separately
The signal cable must be routed separately from potential sources of interference, such as motor supply
cables, 230 V
AC
power cables etc.!
Interference caused by cables routed in parallel can influence the signal form of the test pulses and thus
cause diagnostic messages (e.g. sensor errors or OpenLoad errors).
D: Distance between the cable ducts should be as large as possible
blue arrows: signal line
red arrows: potential source of interference
The common routing of signals together with other clocked signals in a common cable also reduces the
maximum propagation, since crosstalk of the signals can occur over long cable lengths and cause diagnostic
messages.
If connection via a bus cable is unavoidable, the test pulses can be switched off (parameters Testing of
outputs active and Current measurement active). However, this then leads to a reduction in the degree of
diagnostic cover when calculating the performance level.
Test pulses
The typical length of test pulse (switching from 24V to 0V and back to 24V) is 300µs to 800 µs. Testing
usually takes place 5 to 7 times per second.
Test pulses for the outputs
The following diagram shows a typical test pulse curve for the four outputs of an EL2904. The
parameters Current measurement active and Testing of outputs active are enabled.
Fig.12: Typical course of test pulses of the outputs
5.2.4 Mechanical installation
DANGER
Risk of injury!
Bring the bus system into a safe, de-energized state before starting installation, disassembly or wiring of
the devices!
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