Delphin ProfiMessage, Hardware Manual

Page: 215 / 322

Profi Message
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 . Earth
loops can however occur between the sensors of different channels of a module.
To avoid such loops, we recommend the use of earth-free sensors or signal
sources.
See also
Potential differences .
Measuring device—computer earth loop
Most of the device's interfaces are galvanically isolated towards each other and
towards the central device. The earth loop through the communication circuit as
shown in the example does not occur with this device.
Use these interfaces to connect the device to PCs, PLCs or to other manufacturers’
equipment.
See also
Galvanic isolation .
7.4 Shielding
Measurement signals can be disrupted by the occurrence of magnetic and electric
fields in the measuring circuits, for example generated by neighbouring current-
carrying circuits. Shielded cables should therefore always be used for sensor cir-
cuitry and kept at least 50 cm away from other current-carrying circuits.
The smaller the sensor signal and/or the higher the sensor impedance, the more
important good shielding becomes for a low noise, accurate reading.
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Delphin Technology AG
Dezember 2015
Profi Message Manual