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.

Q- voltage source of 12v is driving the circuit.if circut draw the current of 0.5A them source voltage will became 11.8v.what is the power dilevered by source when circuit draw 5A current ?

4 Answers   Ecil,

---

define feed forward control loop with example and drawing?

0 Answers   Honeywell,

---

TEMPERATURE VARIATION FOR FREQUENTLY.

0 Answers   TVS,

---

Explain bernoulli’s theorem.

0 Answers  

---

Reason for capillary type dp level transmitter fluctuation

0 Answers   BMB, Enppi,

---

GWR radar transmitter working principle?

2 Answers   Tata Steel Limited,

---

HOW CAN I CONNECT ROSEMOUNT 3300 LEVEL TRANSMITTER TO Allen-Bradley SLC500

1 Answers  

---

what is PM/CM/RCM?

2 Answers   Emco,

---

HOW THE ORIFICE & PRV SIZING BE HAPPENED -- EXPLAIN IN BRIEF

3 Answers  

---

Why Bently Nevada use negative voltage for vibration probes?

4 Answers  

---

Is there’s power on the bus (if so, state whether on the signal bus, or on a separate in the following: a) HART b) Profibus DP c) Profibus PA d) DeviceNet e) Foundation Fieldbus

1 Answers   EIT,

---

how do u calibrate the vacuum transmitter if it shows more reading

0 Answers  

---