Answer / kishore kumar

Distance is the main concideration, as distance increases
voltage drop will be increased where current remains same

Answer / rakesh kumar n

There won't be any current drop in mA, but when you consider
Voltage there will be Voltage drop.

-->main Reasons for Voltage drop

#Distance between the Field and Control Room(more the
Distance and more will be the Voltage drop)

#Consider if the Distance is small between the Field and
Control room,then also there will be Voltage drop,because it
is milli Volt

#Theory Sum of the incoming current and Out going current
is always Zero 20mA=20mA by KCL, if you find any thing
wrong,you can check it in Transmitter Outlet and the DCS
Inlet will have the same milli Amp.

Thank you
Rakesh Kumar.N
INSTRUMENTATION ENGINEER

Answer / mahesh soni

Distance is the main concideration, as distance increases
voltage drop will be increased where current remains same
due to ohms law there is

I=V/R SO CURRENT VWILL SAME any time or no lossed by
wire resistance so v can lay cables long root laying in
plant& all instruments draw curren not voltage

Answer / mohammed abbas

As length of the cable increses the line resistence also
increse, but the current remain same, suppose if your
using the long cable assume 50mtr the line resistance
assume 2 ohm for 50mtr, for 100mtr the line resistance will
be double 100=4 ohm. as per ohmns law. if you are measuring
the flow parameter for 50 mtr and another 100 mtr for same
process condition the reading will be diffrent, suppose if
your are using millivolt means but milli amps will remain
same.
the volatge will increse or decerse as the lenghth incerese
of decerses, but current remain same that is what milli
amps will be used

Answer / pankaj kumar (iert)

* voltage pickup more noise as compare to current.
* if we use voltage signal then chance of its drop.
*

Answer / vijay vaidya

ya i m agree wid mr. kishore

Answer / mohammed

because we cannot lay a cable for more than 50 m to carry mV
signal whereas we can connect current signal cable because it
is less diameter, will not affect by noise and not costly in
addition can be connected for long distances

Answer / delta_v

That's due to voltage drop :)
As simple as that...

Answer / shankar prasad p

MV if transmitted over long distance in wires, voltage
drops occurs leading to variation in actual value.where as
if we transmit mA signal over cable voltage drop not takes
place so we can get actual readings.

Answer / ashutosh

in series the current remain same so the loss of current
due to wire res is not into the consideration in mA but it
is there in mV

can a control valve works without positioner?why need tunning of c/v?

4 Answers  

how to calibrate level transmitter

2 Answers   Reliance,

i want formula for flow control.am doing project in flow control using orifice . i know value of the flow level(Q) . upstream(p1) pressure, orifice diameter(Do) , pipe diameter(Di) and oil viscosity(Vi) how can i calculate downstream pressure

0 Answers  

how to set calibration range in a DP transmitter to measure level for a closed tank and for an open tank,and also please explain me how to set calibration range for a DP flow transmitter in a line ?

1 Answers   CCL Products, IOCL,

What is inside the PLC panel? How does instruments communicate to DCS computer via PLC? What is the type of wiring in PLC connections? Please answer... Thanks

1 Answers  

Can DP transmitter with orifice plate works on Beta ratio 0f 0.3 and differential pressure of 100 MMWC in liquid service application?

1 Answers  

In your own words, would you expect an ultrasonic level device to work better in a pressure vessel with a high pressure or a strong vacuum, and why?

1 Answers  

can u briefly explain aboutan aryton shunt multirange DC ammeter?

0 Answers  

WHAT IS INSTRUMENTATION?

17 Answers   ITC Infotech,

Which buffer solution is used for PH transmitter calibration?

3 Answers  

different between calibration range and instrument range ?

2 Answers  

What is the difference between local indicator(flow) and flow indicator?

2 Answers