ABB ECA06 Configuration And Installation page 40

2.4 Electrical Installation
Grounding and Common Mode Voltage (CMV)
Ground loops can arise when the return wire or the sensor are grounded locally at
their point of installation and the analog inputs have fixed reference grounds. The
inputs should then be connected as differential inputs, i.e. with floating ground
references so that the inputs are floating with respect to the signal ground. Such
an input can receive a CMV within the range –5 V to +17 V measured from the
input negative pole to the supply ground. If it is anticipated that the CMV will be
outside this range then an isolation amplifier must be used. An example of a
ground loop is shown in Figure 24.
Figure 24
40
Example of a Ground Loop.
Chapter 2: Installation
Loop
Current
493-0736-11 (6-2)