Answer / arindam

why we require a 4-20 mamp for transmission? the main reason
behind it because of electro magnetic interference the
voltage can get interfered very easily and we can't get our
desired o/p value.when we are using 4-20 mamp this problem
is solved but since, PLC is a digital device it can
understand mainly High=5V or low so we design the sink to
have a resistance as high to get the desired voltage, the 4
mamp is also helpful to power the electronics at the
transmitter end. to have a 4-20 mv instead can firstly :
cause em interference and secondly we need to have a
continuous level monitoring for different voltages...which
can increase the size of PLC . Also because of change of
impedance at the transmission line the voltage can drop
below 4 volt ocassionaly then loop powering of field
instrument will not be possible.

Answer / biswarup das

There is different module in a PLC . Out of which one is T/C
module if you connect the o/p of T/C directly to this module
of PLC , then the PLC will recognise it.

T/C module is not inbuilt we have to select it seperately.
There are many modules like this such as RTD module, 0-10
volt module etc.

Answer / altamash

In plc, there is a separate I/O MODULE FOR T/C which already have inbuit converter so we dont have to worry on this,First we have to know complete module of plc.thanx

Answer / guest

we will convert mV in to the ma....by connecting resistance
in parallel

Answer / kishore

There will be a Convector for mv to ma what ever the
temperature Sens by the t/c that will convert to the ma and
signal goes to DCS.

Answer / sattar

Voltage to current converter using op-amp

Answer / sreekanth

standard thermocouple output is 0 to 10 mV. There will be 4-
20MA converter either in DCS in the field(Transmitter)as
the modules will accept only 4-20 MA output.

what's the reson that,Load is not same on VFD I/P and O/P Side.whenever DOL condition load is same I/P and O/P side.

2 Answers  

How can SmartPlant Instrumentation users take advantage of these global services?

1 Answers  

what is o2 analyzer and how it measured ,what is the role of this analyzer in cfbc boiler...

2 Answers  

which flow meter is use for measuring the open channel flow?

2 Answers  

I want to measure level under vaccum by using DP Tx and vaccum vary between -500 to -670 mmHg and process fluid is accetic anhydride if consider process fluid density 1 kg/cm2. how to calibrate Tx ? consider level is 0 to 100 Cm.

1 Answers   CCC,

how to calibrate transmitter online (in running plant)please explain correct procedure

4 Answers   Sabic,

What are the disadvantages of Human-Machine Interface (HMI)? atleast 3.

1 Answers  

Why we use 4 to 20 mA, (This is International Standard) instaed of this can we use 4-16, or 4-24 or 3- 15 or any other range

13 Answers   ONGC,

yokogawa Temperature transmitter showing Error 15 which is Reverse Cal Fail (confirmation calculation result is bad) in manual they mentioned reasion That the output goes to the value set by hardware failure mode jumper. How can solve this problem ? anybody can say solution

1 Answers   GTL,

When a timer is placed in RS Logix 5000 with preset value less than its scan time it is malfunctioning. i.e., if the preset is set to 30ms still the timer TT bit is counting till 150ms(its scan time). Any solution for the problem?

2 Answers   Balco,

Which boiler is use in power plant

1 Answers   Jindal,

what is the difference b/w normal thermocouple and skin type thermocouple?

1 Answers   Heisco,