Answer / vinoth

the destination of any signal will be a Controller.
Take DCS, its input supply will be 1-5V.
from instruments, across a 250ohm resistor, the value will
reach DCS as desired 1-5V.

expl:
say 4ma is the output of transmitter.
V=IR,
V=4ma * 250 ohm
V= 1V,
say 20ma,
V=20ma*250ohm
V=5V.

Answer / dhanabalan

It is where the linearity is maintained (4-20 mA Signal).

Answer / t.naveen babu

The reasons for the 4-20 mA standard (and, before it, the
10-50 mA standard) have a lot to do with the original 3-15
psi/20-100 kPa air
signal. The origin of the suppressed or "live" zero in the
pneumatic system was two-fold - if you want to reduce a
passive pneumatic signal quickly, you need to maintain some
differential between the pressure and the "sink" - in this
case, atmospheric air. The basic characteristic of a
flapper-nozzle assembly also has a bit to do with it -
the "linear" range of the flapper pressure is about 3 - 15
psi for a 20 psi supply. Next question - why a 20psi
supply? Anyone else remember 6-30 psi equipment for
final actuators needing a bit more grunt??

The original electronic instruments were direct imitations
of the pneumatic systems with bellows replaced by magnet-
coil assemblies. The first I came across were used in a
geothermal power project (1958 vintage)where the pressure
at the power station was controlled by manipulating valves
in the steam field 1 1/2 miles or so away. The flapper-
nozzle was replaced by a
contact moving between positive and negative terminals - I
guess a bity of mains hum in the amplifier kept it
jittering. In the mid-70's Foxboro produced a range of
pressure transmitters using the magnetic principle which
used the same basic mechanism as their pneumatic equipment -
but the size of the coils made the assemblies a lot
bigger ...

Answer / abhishek

this 3-15 psi later used in electronic signal as 4-20mA. 4mA
used as live Zero , & 20mA is current so
20mA*24V=480mWatt. this power if we increase any signal
wire can cause such type of arc that can cause Fire.

Answer / ahmad

1- Any electronic circuit having its error, here Ico=3.85 ma(aprox=4 ma). that is why we do start from 4 ma.
2- it is also convertable to 1-5 volt, with precision resistance of 250 ohms.

What is hp & mp seperator .& what is its working principle ?

0 Answers  

---

the 3 most common transmitter protocol being in refinery or qatar gas and aramco.

0 Answers   Shell,

---

protection relay watchdog contact operation?

0 Answers   L&T,

---

How to check vortex flow meter is in good condition while we do not having calibration setup?

4 Answers  

---

tell about various protocols used in different plcs

3 Answers   Emerson, Samtel,

---

---

what do u mean by 2/3 soleniod valves?

8 Answers   Nile Sugar,

---

please send the drdo exam paper

0 Answers   DRDO,

---

How to calibrate DP tramitter in flow measurement application? consider my range of flow is 0 to 2000 kg/hr ? please give calculation of , How much pressure applied on low pressure side and high pressure side please give detail of calculation .... It so important for me please reply as soon as possible

1 Answers  

---

Manipulation of dead wt. tester double piston type.

0 Answers   CCIE,

---

how u calculate ai/di/ao/do capacity in ur dcs?

1 Answers  

---

What is difference between reset and initialization in system.

1 Answers   Marafiq,

---

What the basic of communication?

4 Answers   Schneider,

---