Fig. 152: Connection of passive-type analog sensors (current) to the analog inputs
Current 4...20 mA 1 channel used
The measuring ranges are described in the section Measuring Ranges
Ä
Chapter 1.7.2.2.8
“Parameterization” on page 794
Ä
Chapter 1.7.2.2.11 “Measuring Ranges” on page 802:
CAUTION!
Risk of overloading the analog input!
If an analog current sensor supplies more than 25 mA for more than 1 second
during initialization, this input is switched off by the module (input protection).
Use only sensors with fast initialization or without current peaks higher than 25
mA. If not possible, connect a 10-volt zener diode in parallel to I+ and I-.
Unused input channels can be left open-circuited, because they are of low resistance.
Connection of Active-type Analog Sensors (Voltage) to Differential Analog Inputs
Differential inputs are very useful, if analog sensors are used which are remotely non-isolated
(e.g. the minus terminal is remotely earthed).
The evaluation using differential inputs helps to considerably increase the measuring accuracy
and to avoid earthing loops.
With differential input configurations, two adjacent analog channels belong together (e.g. the
channels 0 and 1). In this case, both channels are configured according to the desired operating
mode. The lower address must be the even address (channel 0), the next higher address must
be the odd address (channel 1). The converted analog value is available at the higher address
(channel 1).
The analog value is calculated by subtraction of the input value with the higher address from the
input value of the lower address.
The converted analog value is available at the odd channel (higher address).
Communication Interface Modules (S500) > CS31
2019/04/17 3ADR010121, 13, en_US 789
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