Answer / jose

Instruments have a nominal resistance of 250 ohms. With
that, the usual output of field instruments is 1-5 volts or
4-20 mA. If you put a 250 ohm resistor on a 1 volt output
the the result will be .004 amps or 4 mA. The same holds
true if you put a 250 ohm resistor accross a 5 volt output
you will get .020 amps or 20 mA.

Answer / vijay

usually there exsist linear relationship between this range
when you plot pressuer verses current graph. so depending
on application we can select o/p as 4-20mA or 3-15 psig.
also
for long distance transmission 4-20mA is good

Answer / rajesh mistry

1> Liner Scale
2> Live Zero as a electronics
3> Active signal for pneumatic equipment.

Answer / karthik

The Electronic circuits employed in all Instruments require
atleast 3 mA for its actuation so the lowest range is
limited to 4mA & the rest as said by JOSE is exactly correct

Answer / ravi kiran

After observation of current functioning engineers finalized
that at 4-20ma the current is having linear and constant
properties. Below 3ma and above 25ma the current properties
are different.

Answer / s

there are two reason live zero and other is linearity..
if we divide the 4-20ma in four part it will show more
linearity than 3-15ma

What is the use of control cable?

0 Answers  

Explain working principle of lvdt?

0 Answers  

how to measure the output of RTD given the general formula of  rtd.  

2 Answers  

What is instrumentation control?

0 Answers  

who discoverd ohms law?

6 Answers   HPCL, Patni,

A motor is taking 15 Amps at no load and 60 Amps at full load. and a valve has to open 10% at full load and 80% at no load. How to draw ladder logic.(PLC).

2 Answers  

what is the path to communicate from profi to ofc.what is the means of communication.what is multi cire cable in ofc.

1 Answers  

when we calibrate the DP transmitter at that time which matrial we used in pressure pump?

4 Answers  

Identification of control valve parts.

0 Answers   CCIE, Oil and Gas Jobs,

What is mean by Ethernet, Device net and Control net? For what application we are using these?

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,

what is ABB DCS SYSTEM?

2 Answers   OMV,