Application Manual CDA3000
2-15
2 Inverter module CDA3000
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A
DE
EN
FR
DE
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2.6 Isolation
concept
The analog and digital grounds are isolated from each other in order to
avoid transient currents and interference over the connected lines. The
analog ground is connected directly to the inverter module processor. It
serves as the reference potential for analog reference input. The digital
inputs and outputs are isolated from it. Disturbance variables are thereby
kept away from the processor and the analog signal processing function.
To enhance operating safety we recommend that the analog and digital
grounds should not be interconnected.
Figure 2.3 Voltage supply to I/Os
When selecting the cable, note that the cables for the analog inputs and
outputs must always be shielded. The cable or wire core shield on
shielded pairs should cover as large an area as possible in respect of
EMC considerations. In this way high-frequency interference voltages are
safely discharged (skin effect).
Special case: use of an analog input as a digital input
Use of the internal 24 V DC as the supply voltage when using an analog
input with the “digital input” function requires connection of analog and
digital ground. For the reasons mentioned above, this can lead to interfer-
ence, and demands extra care in selecting and connecting the control
cables.
analog
digital
M
3~
I/O
I/O
SNT
R
B
+24V
+10V
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