If AGND does not get connected to ZP, the sensor current flows to ZP via the
AGND line. The measuring signal is distorted, as a very small current flows
through the voltage line. The total current through the PTC should not exceed
50 mA. This measuring method is therefore only suitable for short lines and
small sensor currents. If there are bigger distances, the difference measuring
method should be applied.
Voltage
0 V...10 V
1 channel used
Voltage
-10 V...+10 V *)
1 channel used
*) if the sensor can provide this signal range
In order to avoid error messages or long processing times, it is useful to configure unused
analog input channels as "unused".
Connection of passive-type analog sensors (Current)
UP
ZP
1.0
I0-
1.1
I1-
1.8
UP
1.9
ZP
PTC
2.0
I0+
2.1
I1+
2.8
UP
2.9
ZP
4 ... 20 mA
-
+
Fig. 58: Connection example
Current
4 mA...20 mA
1 channel used
CAUTION!
If, during initialization, an analog current sensor supplies more than 25 mA for
more than 1 second to an analog input, this input is switched off by the module
(input protection). In such cases, it is recommended to protect the analog input
by a 10-volt Zener diode (in parallel to I+ and I-). But, in general, sensors with
fast initialization or without current peaks higher than 25 mA are preferrable.
Unused input channels can be left open-circuited because they are of low resistance.
Connection of active-type analog sensors (Voltage) to differential inputs
Differential inputs are very useful if analog sensors are used which are remotely non-isolated
(e.g. the minus terminal is remotely grounded).
Device specifications
I/O modules > Analog I/O modules
2022/01/31
3ADR010278, 3, en_US
508
