NORSTAT Safety Relays - Handbuch (Seite 32)

application guide safety relays from riese electronic page 31
5 Safety mats according to EN 1760
Safety mats are used to protect dangerous areas,
which can be found in presses, robotic cells and
other movable tools. Stepping on the mat results in a
signal to the control stopping the dangerous
movement.
Safety contact edges
Safety contact edges were used for protection from
squeezing e.g. at roll gates or elevators.
If somebody presses the contact edge immediately a
stop signal is released.
Principle of Safety Mats
Safety Edges and Bumpers follow the same principle as safety mats, so we will focus on the safety mats
without loss of generality.
4-Wire-Principle
The 4-wire-mat recognizes an activation by a short circuit between the two elements (R
12
, R
34
). Inside of
the mat all connectors are connected (1-3, 2-4). Because all 4 wires have to be connected to the
controlling device, the amount of wiring is quite high.
1 2 3 4
function table mat free mat entered
fault
(broken wire)
R
12
, R
34
∞ 0 -
R
13
, R
24
0 0 > 0
R 12 means the measured electrical resistance between the clamps 1 and 2, the
others resistances respectively.
Category: up to 3
2-Wire-Mat
The structure of the 2-wire-mat is identical to the 4-wire-mat, but two of the clamps are not wired to the
controlling device but finalized by a – normally - 8.2 kΩ-resistor. The amount of wiring is less.
1 2
8k2
function table matte frei mat entered
fault
(broken wire)
R
12
8,2 kΩ 0 > 8,2 kΩ
R 12 means the measured electrical resistance between the clamps 1 and 2, the
others resistances respectively.
Category: 2
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