Answer / dinesh priyadarshi

1)1-5Vdc have voltage drop at longer distance. It is only
loop voltage for 4-20mA signal
2)4-20mA gives linear output
3)All the eletronics circuit have a leakage current range
between 0-3mA. so for perfact meausre of curent we start
from 4 mA
4)If we see the span of 4-20mA is 16 mA. We are using
digital eletronics, so we have achieve good resolution with
16 bit resoution with successive approxiation DAC. We can
say i the step of 65,353 in terms or digital count for
processor.
5)4 mA is also called live zero. If cable may cut or damage
transmitter shows you 0 mA. So we cannot differentiate
between our signal so we used 4mA as live starting signal.
So if cable cut or damage we get 0 mA.
6)We use 20mA as maximum current because between 4 to 20 mA
we have get linear output.

Answer / sikandar mehra

to differentiate live and dead zero.........

Answer / adrianmlopez

When we use 1-5V in the loop, it may have some loses to the
destination point since voltage dissipated when the
conductor is very long.When we applied current, it can't be
dissipated even a kilometers away from the source to the
destination point. Since we do an instrumentation,
instrument or equipment needs an accurate value,we do not
use voltage but 4-20mA instead.But it may depend on some
other applications,for instance if your output variable
needs voltage,why used 4 to 20mA, right.

Answer / amit

because if wire is broken or signal not come so we are
check that cable working or not so we are using 4-20ma.

Steve said that "An eddy-current probe works by passing an alternating current through a coil of wire and measuring the coil’s impedance" while we are using -24 Volt DC , So I am confused about DC and AC. Plz .

2 Answers   Jindal, Sadara Chemicals,

---

ON RADAR INTERFACE LEVEL TRANSMITTER IF DI-ELECRIC IS WRONG WITH CONTINIUS PROCESS THAN HOW CAN INDENTIFY OR HOW CAN I PUT NEW DI-ELECTRIC VALUE?(ROSEMOUNT-TDR-3300-COXIAL PROBE TYPE)

1 Answers   Chevron Phillips,

---

what is intools software

2 Answers  

---

when the instrument tapping on pipe line is located below and transmitter is located above the tapping point for liquid service transmitter, what should we do, is there any additional drain valve is required??

2 Answers  

---

What is mean by ATEX?

1 Answers  

---

---

define SIMULATION a and what is the need of it

3 Answers   Siemens,

---

what is weighfeeder

2 Answers  

---

what is sil (safety integrity level

0 Answers   Essar,

---

What is the basic difference between Modbus and CAN Open Protocols

0 Answers  

---

hii my name is sujith...i am preparing for HPVL GET 2010... so ,,,pls help me by send any previous questions or material to my site.....(Msujith_12@in.com) thank q

0 Answers  

---

p=hdg,please explain these parameters?

7 Answers  

---

why I need valve guard and whats different between guard and positioner ??

0 Answers  

---