Answer / guest

A thermocouple measurement involves two thermocouples, one
at hot junction and another, a cold junction, at 0degC.
Maintaining this cold junction at 0 degC is cumbersome, and
it is easier if it can be at room temperature. The
indicated temperature will be lesser by "room temperature
value", and if room temperature varies, then the indicated
temperature also varies. Measures to counteract these
errors is called cold junction compensation. When cold
junction temperature increases, the voltage from
thermocouple decreases. If an equivalent voltage is added
to this, then cold junction errors can be removed.One can
monitor this cold junction (near the terminals where the
thermocouples get connected to copper wires of indicator)
using another sensor, and add an equivalent voltage to
thermocouple voltage to compensate for changes in cold
junction. Alternatively, the ambient temperature measured
can be added to temperature computed from thermocouple
voltage to get CJC.

Answer / vinoth.s

TC works on the principle of SEEBACK's Effect, which states
the the temperature difference is directly proportional to
induced emf, when two dissimilar metals are twisted together
and heated at end.
its equation states,
hot junction - cold junction = induced emf.
its means hot junction is the temperature measured..
cold junction means the ambient temperature unlessly
considering the compensation. we have keep the cold junction
as constant by giving a constant hot source or ice bath. so
that its easy to find the hot junction values.

Answer / guest

cold jn.compensation is achieved by introducing a 3 junction
called compensating jn.which does not allow the temperature of
cold jn.to rise above 1 degree celcius .

Answer / zaheer abbas

Open ended through we received TC output as mv

Please explain about FAT? What is the difference between FAT and SAT?

6 Answers   IBM,

---

i want know about capillary type LT transmitter installation. we can install any location in between to HP and LP leg?

2 Answers  

---

Identification of ss fittings, pilot valves, relief valve.

0 Answers   CCIE,

---

how the arrangement of equipments done in control room

0 Answers  

---

What is the PLC Level & type.

2 Answers   Bhushan Power Steel,

---

---

We are using Rosemount 5400 series Radar Level Transmitters in all types of Sump Applications having oily water hdrocarbon petrochemical nature. What we are facing the problem frequently is that always getting reading frezzed at some value. If we do power recycling , sometimes it is working . then making same freezing problem. If anybody faced before such type of problem and also having solution , Please give the answer.

0 Answers   Sabic,

---

can you tell me how many stages in steam turbine of 10 MW power plant

2 Answers  

---

what is difference between call out and call log

0 Answers   Petro Rabigh,

---

Why 4ma - 20ma signal used in instrumentation??

5 Answers  

---

how to adjust relay in smart positioner ?

1 Answers   SipChem,

---

my temperature transmitter in field showing 700 degree , whereas in dcs showing 459 degree, how to resolve this?

4 Answers   ONGC,

---

why we use 24v dc in instrument rahter than 230vac????

4 Answers  

---