Ensuring that a rotation or
oscillation has ceased is critical if
personnel need access to that part of
a plant. Therefore, it is critical to
select devices that will protect the
workforce by ensuring that such
motion, or lack of it, is detected in as
safe a manner as possible.

The new DA101S zero-speed
safety relay from ifm electronic has
been tested by TÃœVNord for use in
applications up to and including PL
e according to ISO 13849-1, SIL 3
according to IEC 61508 and SILClaim
Limit 3 according to EN62061.

Equipped with two volt-free safety
relay outputs, the slim housing of the
DA101S measures just 25mm wide
and has a solid-state PNP feedback
output as well as LED indicators to
verify the status of inputs and outputs.

As true zero motion is difficult or
impossible to verify, the DA101S is
set by the user to detect a low
frequency, and switch when the
detected pulse rate drops below the
pre-set. This pre-set will vary
according to the pick-up
arrangement and machine
constraints, so one of our
frequencies (0.2, 0.5, 1 and 2Hz) can
be selected using a hard-wired link
that cannot be changed during
operation without the unit switching
into the safe state.