System Manual HS3A-H21M4
16
Determining cable lengths using the example table (see table 2)
Example: 6 switches are to be used in series. Cabling with a length of 40 m is
routed from a safety relay in the control cabinet to the last switch (#6). Cables
with a length of 20 m each are connected between the individual HS3A safety
switches.
Figure 5: Circuit example with six HS3A
A safety relay is connected downstream which consumes 75 mA on each of
the two safety inputs. This operates over the whole temperature range with a
voltage of 19.2 V DC (corresponds to 24 V DC -20 %).
All the relevant values can now be determined using the example table:
1. Select the corresponding section in the column n (max. number of switches).
Here: 6 switches.
2. In column I
OUT
(possible output current per channel OA/OB), find a current
greater than or equal to 75 mA. Here: 100 mA.
It is then possible to determine the maximum cable length from the last
HS3A switch (#6) to the control system from column L1. Here: a length of
50 m is permitted.
Result: The desired cable length L
1
of 40 m is below the permitted value from
the table. The overall length of the switch chain L
max
of 140 m is less than the
maximum value of 200 m.
The planned application is therefore functional in this form.
Safety Relay
L
1
= 40 m
L
2
= 5 x 20 m
L
max
= 140 m
L
n
= 20 m
V
n
= min. 19.2 V
I
out
= min. 75 mA
HS3A # 6
HS3A # 5
HS3A # 4
HS3A # 3
HS3A # 2
HS3A # 1
