Beckhoff EL3182, Документация

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Mounting and wiring
EL3182 39 Version: 1.2
For all channels within the terminal U
CM-max
must not be exceeded.
U
CM
for 0/4..20 mA inputs
If U
CM
of an analog input channel is exceeded, internal equalizing currents result in erroneous mea-
surements.
For 1 and 2 channel terminals the internal GND is therefore fed out to a terminal point, so that the
U
CM
specification can be met through application-specific configuration of this GND point, even in
cases of atypical sensor configuration.
Example 1
The 2-channel EL3012 is connected to 2 sensors, which are supplied with 5 and 24 V. Both current
measurements are executed as low-side measurements. This connection type is permitted, because at I
max
CMP
ch1
and CMP
ch2
are approx. 330 mV above 0 V, which means that U
CM
is always < 0.5 V. The
requirement of U
CM
< 10 V (applicable to EL30xx) is therefore adhered to.
Fig. 33: Example 1: low-side measurement
If the EL30x1/EL30x2 or EL31x1/EL31x2 terminals have no external GND
int
connection, the GND
int
potential
can adjust itself as required (referred to as "floating"). Please note that for this mode reduced measuring
accuracy is to be expected.
Example 1a
Accordingly, this also applies if the floating point GND
INT
is connected to another potential.