Digital Signals

D

Thread Starter

Darker

Analogue signals from devices like PT or LT operate on 4-20 mA current.

It starts from 4 mA and not 0 mA for lots of reasons, the main one being is that if there is a fault in the line, it will send a 0mA, the PLC might think that 0 pressure is there (or any physical quantity), but instead there is a fault in the line.

What about Digital Signals: they are either High (24VDC) or Low (0VDC) doesn't the 0 V creates some sets of problems same with the Analogue signals?

Thank you in advance.
 
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