(RTD) – simple temperature sensing tool. made of conductive material Work on principle of change of resistance of metal with respect to temperature Rise in temperature reduce in resistance of conductive material RTD types are broadly classified according to the different sensing elements used.(Pt, Ni ,Cu)

1. GOVERNMENT ENGINEERING
COLLAGE RAJKOT
Subject: EMI (2141003)
Present by: Borisagar Bhargav
(160200111012)

2. TOPIC :
RTD
(RESISTIVE TEMPERATURE DETECTOR)

3.  CONTENT
 Resistance/temp. relation of metal
 About RTD & Functions
 Classifications of RTDs
 Construction
 Advantages
 Limitation
 Applications

4.  RELATION BETWEEN TEMPERATURE AND
RESISTANCE
 Rt = R0[ 1+ X1t + X2t2 ]
 X1 & X2 are constant and it is different values for
different metals.
 Rt is the resistance of temperature at temperature “t”.
 R0 is the resistance of temperature at room
temperature T0.
 “t” is the change in temperature.

5.  ABOUT RTD & FUNCTIONS
(RTD) – simple temperature sensing tool.
 made of conductive material
Work on principle of change of resistance of metal
with respect to temperature
Rise in temperature reduce in resistance of
conductive material

6.  RTD TYPES
RTD types are broadly classified according to the different
sensing elements used.(Pt, Ni ,Cu)
 Platinum
 best metal for process type RTD’s.
 withstand oxidation and is effective over a range of –200
to + 850 degrees C.

7.  Copper
- The greatest strength of this metal is its low cost.
-measure temperatures as high as 120 degrees C.
 Nickel
- good compromise between copper and platinum.
-has a higher output and is slightly less expensive than
platinum.
- extremely nonlinear above 300 degrees C.

8.  CONSTRUCTION

9.  The simplest type of open wire construction of platinum
resistance thermometer(PRT).
 The platinum wire is wound in the form of spirals on an
insulating material such as mica or ceramic.
 This assembly is fired at high temperature to assure
annealing of the winding.
 The assembly is then placed at the tip of probe as shown in
figure.
 This wire is in direct contact with the gas or liquid whose
temperature is to be measured.

10.  This gas or liquid however should not be corrosive or
conductive.
 The resistance of the platinum wire changes in
temperature of the gas or liquid.
 The maximum temperature measurable in continuous
operation is 1000*K i.e. 727*C
 This type of sensor have a positive temperature
coefficient of resistivity as they are made from metals.
 The wire is direct contact with the gas or liquid whose
temperature is to be measured.

11.  The other metal used are nickel and copper.
 For many application the platinum resistance wire is
enclosed in a protective tube.
 The tube is made of glass, quartz, porcelain or metal.
 This protect the resistance wire from any mechanical
damage or chemical reaction.

12.  ADVANTAGES
 Very high accuracy
 Excellent stability and reproducibility
 Ability to be matched to close
tolerances for temperature difference
 measurements.
 Ability to measure narrow spans
 Suitability for remote measurement

13.  LIMITATION
Susceptibility to mechanical
damage
 Need for lead wire resistance
compensation
 Susceptibility to self-heating error
 Susceptibility to signal noise

14. CONTINUE…
Unsuitability for bare use in
electrically conducting substance
 Generally not repairable
 Need for power supply

15.  APPLICATIONS
Air conditioning and refrigeration servicing
 Food Processing
 Stoves and grills
 Textile production
 Plastics processing

16. CONTINUE…
 Petrochemical processing
 Micro electronics
 Air, gas and liquid temperature measurement
 Exhaust gas temperature measurement
 Immersion sensors
 Surface mounted sensors