Why any transmitter signal is 4-20 mA only
Why is started from lower range 4 mA and upper range is
20mA.

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Why any transmitter signal is 4-20 mA only Why is started from lower range 4 mA and upper range is ..

if we use 0-20 mA scale for 0-100%,then 0% will be read in two cases;1)when instrument has any kind of damage problem(not responding case)& 2)for the ground level reading.so we use 4-20mA which shows 4mA for 0%(ground level) & 20mA for 100%(full value) and 0mA shows that instrument has any damage problem.And guyz,in the range of 4-20mA the calibration shows linear characterstic too.

 Is This Answer Correct ? 30 Yes 3 No

Why any transmitter signal is 4-20 mA only Why is started from lower range 4 mA and upper range is ..

current output is 4-20 mA.
Let take a transmitter operating range is 0-100%
in this case, 0% is only 4 mA,100%is 20 mA.
Because the transmitter have no power,then its output is
0mA.That means zero , live zero.
zero means there is no process is done.
live zero is transmitter have no power,etc.,

 Is This Answer Correct ? 5 Yes 0 No

Why any transmitter signal is 4-20 mA only Why is started from lower range 4 mA and upper range is ..

because if use 0 -20 mA as 0-100% there is any signal cable
damage or cable open it will show only 0%. if use 4-20mA as
0-100% it will show bad process value(live zero).

 Is This Answer Correct ? 13 Yes 9 No

Why any transmitter signal is 4-20 mA only Why is started from lower range 4 mA and upper range is ..

Upper all answer is right but its 4ma not 3,2,1 bcz it is calculting prove. Has calcultion

 Is This Answer Correct ? 0 Yes 0 No

Why any transmitter signal is 4-20 mA only Why is started from lower range 4 mA and upper range is ..

1. signal is linear
2.no noise
3.current signal will not drop

 Is This Answer Correct ? 0 Yes 3 No

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Q1: Consider part of a control loop, which excludes the transmitter, consisting of a process, a controller and a control valve which may be represented by two dead times of 0.5 min each and three exponential lags of 0.8 min., 1.0 min. and 1.5 min. respectively. We wish to express this system as an overall first order plus dead time (FOPLD) model ie gain, time constant and process dead time. (We will see later that this is often done, to simplify controller tuning). For this exercise, gain is considered to be 1.0. (A) If the transmitter is a flow transmitter whose behaviour can be described by a dead time of 0.2 min. and an exponential lag of 0.5 min. in terms of the overall dead time and overall first order lag how can the system behaviour be approximated ? Overall dead time = Overall time constant = (B) If the transmitter is a temperature transmitter with a temperature sensor in a protecting well whose behaviour can be described by a dead time of 0.7 min. and an exponential lag of 15 min. how can the overall system behaviour be approximated now? Overall dead time = Overall time constant =

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