Thermocouple when senses gives "mv" readings to the
transmitter. RTD gives "ohm" readings to the transmitter.
For checking put the multimeter in resistance mode and if
the the sensor is throcouple the meter will indicate
almost"0" resitance whereas the RTD would indicate
around "119 ohms" in normal temperature like 30deg.C
rtd can be checked by measuring the resistance accross the
terminals. At room temp rtd has got a resistance around
110ohm when neasured across its terminal.
t/c can be checked by measuring mv at the terminals
connected. the corresponding mv is corelated with mv v/s
temperature chart to find the temp.
Thermocouple is basically couple of two dissimilar matel
wire which generate certain emf on puting the couple end in
higher temperature source.As emf is generated then it can
measure in terms of mV.Phisically we can check the T/c by
checking it two wires, they will be of different
RTD is resistance temperature detector works on the basis
of resistance changes when temperature changes. Physically
they can be identified by wire exposed to make
connection.In normally everyone uses three wire RTD, in
which 2 wires are of same insulation colour and resistance
between them will be nearly 2-3 Ohms. The resistance b/w
third wire and any of those wire will be 119.5 Ohms at room
temperature.RTD never generate emf hence we can't measure
any mV b/w any of wire of RTD.
more answers are here. Answer No 7 is currect.
but one thing is missed about the color coding of thermo
couple. mostly in industrial section we are using K, E, J,
T , types we can understand the these types from the color
code of TC. you will get further details on
put multimeter in resistance mode and check for resistance
b/w wires of rtd or thermocouple,If it shows 0 ohm in
normal earth atmospheric temperature it's fine.And There is
no big difference B/w RTD AND THERMOCOUPLE Accorting to the
measurement range(low temp to high temp),Accuracy it is
In control valve , Failure position : Close
If it is Fail close(FC) during failure of AIR.. what will be the initial/ normal position of control valve is it normally open or close? please some one explain soon..