6.2
Prerequisites for the safe operation of the device in a system
WARNING
Risk of injury and damage caused by electrical current!
As a result of equipotential bonding currents between the device and other grounded
devices in the system, faulty grounding of the device can give rise to the following dan‐
gers and faults:
■
Metal housings are vulnerable to dangerous currents
■
Devices will behave incorrectly or be destroyed
■
Cable shielding will be damaged by overheating and cause cable fires
Remedial measures
b
Only skilled electricians should be permitted to carry out work on the electrical sys‐
tem.
b
Ensure that the ground potential is the same at all grounding points.
b
If the cable insulation is damaged, disconnect the voltage supply immediately and
have the damage repaired.
b
Where local conditions are unfavorable and therefore do not meet conditions for a
safe grounding method (same ground potential at all grounding points), take mea‐
sures in accordance with the following formats.
The device is connected to the peripheral devices (voltage supply, any local pulse sen‐
sor(s), system controller) via shielded cables. The cable shield – for the data cable,
for example – rests against the metal housing of the device. The device can be
grounded through the cable shield or through a blind tapped hole in the housing,
for example.
If the peripheral devices have metal housings and if the cable shields also lie on their
housings, it is assumed that all devices involved in the installation have the
same
ground potential
.
This is achieved by complying with the following conditions:
■
Mounting the devices on conductive metal surfaces
■
Correctly grounding the devices and metal surfaces in the system
■
If necessary: low-impedance and current-carrying equipotential bonding between
areas with different ground potentials
SICK
Device
7
4
6
Power Supply
U
=
8
=
9
1
2
3
I
5
System
Controller
Figure 13: Example: Occurrence of equipotential bonding currents in the system configuration
1
System controller
2
Device
3
Voltage supply
4
Grounding point 2
5
Closed current loop with equalizing currents via cable shield
6
ELECTRICAL INSTALLATION
30
O P E R A T I N G I N S T R U C T I O N S | LMS4000
8023198//2018-06-18 | SICK
Subject to change without notice
