Answer / vinoth

In RTD, we are measuring temperature through Resistance
change. Normally we are measuring this parameter in the
field. while transmitting, these signal to control panel
through cable, some additional resistance due to distance
will add upto the RTD resistance value. which shows
incorrect value. in order to overcome these, normally in 2
wire system, we will manual add/subtract some resistance
value with the measured resistance value.but it is no percise
whereas in 3 wire system, a parallely third wire run with
the two polarity wires, but its direction of current flow is
opposite to the other two. so it will cancel the line
resistance and give exact value. similarly, for more precise
and accurate measurement, we mostly use 4 wire system.
In above mentioned description, the addition of resistance
or removal of line resistance through extra wire is called
compensation for RTD

Answer / sandip patel

RTD means resistor temperature detector .its resistance is increase with increasing of the temperature. 2wire RTD is used for direct use of it but 4 wire RTD used when the compansation is needed in plant for removing the errors.

Why we use DPT? can we use PT instead of DPT?

2 Answers  

---

I HAVE GOT TYPICAL PROBLEM WITH THE TEMP.INDICATION. THE PROBLEM IS THE K-TYPE T/COUPLE OUT PUT IS CONNECTED TO A INDICATOR.THE INDICATION FLUCTUATES SOME TIMES AND SOME TIME IT IS STABLE. WHEN I CHECKED OUT PUT OF T/COUPLE THE MV WILL NOT VARY. WHERE AS INDICATION FLUCTUATES. WHEN I GIVE MV SOURCE TO T/COUPLE EXTENSIONCABLE FROM THE FIELD IT INDICATION IS STABLE. WHEN GIVE MV SORCE TO INDICATOR ITS INDICATION IS STABLE. PLEASE CLARIFY.

5 Answers  

---

in my plant 100% feedwater control v/v is air to close but due to instrument air fail,the valve opens but instead of drum level high its get tripped in low low drum level.the urv of level tx is 0 and lrv is -800.pls tell me the reason. for such behaviour.

1 Answers   Sirpur Paper Mill,

---

as an instrumentation engineer which are the things we have to know / or we must have idea about that....

2 Answers  

---

Explain , how timer based pneumatic control valve will work ?

1 Answers  

---

---

What is Difference between Bench Set & Operating Range of Control Valve?

1 Answers   AB Sugar,

---

How can i solve the problem of ROSEMOUNT 5300 guided wave level transmitter of full range? For more clearfication , another guided wave level transmitter VEGA brand have the same problem and i solved it by drain the champer from water and make "false signal suppretion" from transmitter push buttons it's configuration to tell the transmitter to avoid any built-up signal ,,, so my question how can i avoid the problem that rosemount read full range while the champer empty or any other ????

1 Answers  

---

why micro controller 8051/52's clock frequency is internally divide by 12 ?? and why it is further divide by 32 in UART serial communication ??

1 Answers  

---

what is lead lag compensator and for wat v using that???

3 Answers  

---

Hi Friends i am going to write BARC written test by this month 20th (20-5-2008). So please if any body knows the details about this or having previous question papers pls mail me to kkumarei@gmail.com. For Suggestions give one message to 9962122264

0 Answers   PDIL,

---

can we use a control valve without positioner

19 Answers  

---

Why we not use 2-20Ma or 1-20Ma

5 Answers  

---