Answer / chandrasekarapandian

4-20 mA is the universal standard.
Justification:
1. easily splittable ranges 0 % = 4mA
25 % = 8mA
50 % = 12mA
75 % = 16mA
100 % = 20mA
2. 4 to 20 mA passed over 250 ohms coil resistance will
produce a suitable voltage sourcew of 1 to 5 volt.
3. LIVE ZERO
If our sensor to PLC wire connecton is open PLC reads 0mA
where as if the input of sensor in ZERo PLC reads 4mA.

Answer / srinivasan narayanan

Most of the Transmitters output used 4 -20mA. This is because to identify whether the transmitters are live or not

if the Transmitter shows 4 mA it's a live Zero

if the Transmitter Shows 0 mA it's a Dead Zero

Answer / seshu

when we are using 0 to20ma if any case cable is damage it
carry o ma signal continues so we are using 4 to20 ma

Answer / kalpit thakkar

Instrument has own Load of 3mA. so we go for 4-20mA. & Also IEC Approved to 4-20 mA.

Answer / rathod mukesh

0 - 20 ma range is not use in the instrumentaion as standard range because if we use 0 ma for zero process parameter value, if any reason loop wire become break although plc or micro controller get 0 Value at unkown process parameter value and its understand process is in healthy condition but actcully fault is occur in physical data(0-20 ma) transmission link . the plc or micro controller is not accept proper value of process prameter. And we cant define live zero of process parameter. Use to 4- 20 rane ma we easily define live zero.

Answer / rathod mukesh r

If we use 0 - 20 ma rage as standard then we cant define live zero .

Answer / nilesh

This is a universal standard adopted.4 mA at 0% ensure live
zero.

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