Expert
Logger
Connect the PE terminal with a ≥ 2.5mm2 cable to the
protective earth of
your power supply.
6.3 Earth loops
By linking sensor, measurement device, and computer, connections then
exist between different ground points. Unless the individual devices are
connected to protective earth, this electro conductive connection creates
an electrical circuit between the devices. The result is what is known as an
earth or ground loop (shown red in the example).
This can have the following effects:
l
In practice the earthing points U1 to U3 shown in the graph do not neces-
sarily possess equal potential. Constant or changing potential differences
can occur between the earthing points due to the earthing plan and wiring.
Compensating currents then occur in the sensor and communication cir-
cuits.
l
Interference in the sensor or communication circuits, for example through
electromagnetic fields, enable parasitic currents to occur within the circuit.
Compensation and parasitic currents lead to interference or noise voltage
at the input of the measuring instrument and thus constant or shifting
errors in measurement.
Prevent earth
loops.
Sensor—measurement device earth loop
Galvanic isolation of the inputs to the central device, means earth loops via
the sensor circuit as shown in the example, can not occur within the device
263
Delphin Technology AG
Januar 2018
Expert
Logger
Manual
