Answer Posted / jaldeep
For signal transmission we are using 4 to 20 mA, because of
following reasons.
1. If you are using 0 to 10 for long distance then
signal will be dropped due to cable resistance you will not
get correct feedback
2. 4 to 20 mA will give correct feedback even for
long distance. It will not drop according to cable
resistance. Only you have to keep loop impedance as per
your field instrument.
3. Open loop, you can easily detect in 4 to 20 mA.
You can program if mA is less than 4 then you can define it
as open loop.
4. For 0 to 10 v input if cable is open then it will
be difficult to identify that cable is open or input is 0
volt.
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