Beckhoff EL3702, Документация

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Mounting and wiring
EL37x2 48 Version: 3.5
Fig. 38: Internal connections for 0/4..20 mA inputs of a EL3xx2
For all channels within the terminal U
CM-max
must not be exceeded.
Note
U
CM
for 0/4..20 mA inputs
If U
CM
of an analog input channel is exceeded, internal equalizing currents result in erro-
neous measurements.
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. 39: Example 1: low-side measurement