Answer / lokesh gatty

We cannot control through thermocouple/RTD, they are only
measuring elements,which is connected to temperature
controller which as set value for which point it has to
control temperature (PID/Relay logic control)..Meanwhile
Temperature transemeter is used to convert mv/ohm to anolog
signal(4--20 ma)...we have to refer ohms/mv to degree Celsius
table

Answer / aditya kaushik

When we are using the rtd/thermocouple, The output is in mv
or Ohm variation wrt temperature, that will nt be directlyy
processed by our dcs/PLC so we are using transmitters to
convert it to 4-20 ma accordingly, bt now a days rtd cards
are available widely with plc vendors so we can now a days
use directy without transmitters also,\\thnx,

aditya

Answer / george mathews

Neither temperature transmitter not the thermocouple or Rtd
can control the process. Because as we know Thermocouple and
RTD are nothing but measuring medium , their only work is to
measure the temperature , and for the transmitter it nothing
but a transducer whose only work is to send the measurement
in d form of mA (4 to 20 mA.)

Answer / palanisamy

If you transmit Thermocouple/RTD signal for a longer
distance, it can easily pickup noise & you will not get a
steady reading in the receiving instrument. By providing a
temperature transmitter, we can avoid noise pickup.

Answer / chandrakant kale

WE GENERALLY NEED TO CONTROL THE PROCESS PARAMETER
(TEMPERATURE) SO FOR THAT WE NEED TRANSDUCER.WHICH SEND 4-20
MA TO THE DEVICE WHICH IS TO BE CONTREOLLED. TC IS ONLY FOR
SENSING TEMP.

what is "smart" in smart transmitter ?

4 Answers  

Witch type cable use for rtd ,why?

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I have observed in field instrumentation work... I remove the fuse of an analog transmitter then it shows 7.75 kg/sq cm (which is practically wrong value)in DCS and when put the fuse it shows 0 in dcs. Then cheach the field transmitter termination and found moister. clean that and then it shows 1.1 kg/ sq cm which is right value. Please describe the above phenomenon.

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sir ,iam in dem urgent need of HPCL Paper of Instrumentation Branch plz send me at your earliest convenience at ujjwal_sharma1983@yahoo.com

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which type of zones used for boiler? & why ?

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what is the difference between transmitter and converters?

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What is open loop and close loop?

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relation between flow and differential pressure.

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what is proportional & what is proportional band

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what is actual drum level and compensated drum level?

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As you are fresher in Instrumentation & control engineer.Then why should I select you?

1 Answers