Compliance, safety, and intended use
17
Mako U Technical Manual V1.1.3
Ground loop explanation
Ground loops can occur only for camera applications including both:
•
PELV-powered devices in the machine application
•
Use of camera GPIOs
With the graphics on the following pages, you can easily recognize if ground loops
may occur for your application.
Abbreviations
I/Os
Opto-isolated in and outputs
GPIOs
Non-isolated general purpose in and outputs
PE
Protective earth
PELV
Protective extra low voltage
PLC
Programmable logic controller, such as Siemens SIMATIC
Ground loop factors
PELV on PCs
PELV power supplies are used to better protect the user from injuries and death.
PCs are equipped with PELV power supplies.
USB ground
USB ground is connected to the PE of the PC mainboard that is connected to the
PELV power supply of the PC.
PELV devices
PELV-powered devices in the environment of the machine application bear the risk
of a ground loop.
PELV ground
The PELV power supply’s output zero conductor is connected to the ground of the
device. Through the line power supply, this PE conductor is connected to earth.
Fault currents
On PE, fault currents up to 2500 V can occur that are caused by such as:
•
Machine defects in the environmental setup
•
Friction from ground movements or moving machine parts
•
Chemical processes in the ground.
Ground loop risks
Ground loop
If a device of the environmental setup has a PELV power supply, it is connected to
PE as is the PC; a ground loop is created.
Material damage
A fault current can destroy the camera or connected devices, such as the PC or
peripherals.
