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Measurement of temperature using RTD (Pt – 100).

 

EXPERIMENT NO. 7(a)

OBJECT: -Measurement of temperature using RTD (Pt – 100).

APPARATUS REQUIRED: - RTD kit, heating arrangement, Ice, Thermometer, H2O

THEORY: - This type of transducer is used for temperature measurement. Here the basic concept used is that electrical resistance of different metal changes in accordance with the temperature i.e. for temperature measurement. Principle used is that the resistance of a conductor changes in proportion with the change in temperature. The unknown temperature is determined in terms of electrical resistance of the conductor, which senses the temperature. The change in resistance of this device is precisely determined either by bridge circuit or by ohmmeter.  Resistance of a conductor changes with change in temperature. This property is used for the measurement of temperature and each transducer is called Resistive Thermometer and falls in the category of electrical resistive transducer. The variation of resistance ‘R’ with temperature ‘T’ can be presented as:

                                                R=R0 (1+α1T+α2T2+…)          

Where    R0=Resistance at 00C

α1,α2  are constants

                           

Generally the metals used are Platinum. This is used because of following features: 

  1. Platinum provides good stability and accuracy.
  2. It can operate on wide range of temperature.
  3. It has good linearity over wide temperature range.
  4. Less errors during operation.

 

CIRCUIT DIAGRAM:

 

FIG7.1-: CIRCUIT DIAGRAM OF RTD

 

PROCEDURE: -

 

  1. Connect the input power supply to main power.
  2. Switch on the power supply, the red LED will glow.
  3. Connect the RTD source/sensor at a pin connector & 1000C temperature is calibrated. 

 

OBSREVATION TABLE:-

S.No

Temperature

Display Reading (mv)

1.

Temp with Ice point

 

2.

Temp with Boiling Point

 

 

 

 

 CALULATION:-

 

                             R=R0 (1+α1T+α2T2+…)

            Where    R0 = resistance at 00C

                        α12 are constant.

RESULT:-  we measure the temperature using R.T.D.

PRECAUTIONS:-

  1. Handle all equipments with care.
  2. Make connections according to the circuit diagram.
  3. Take the readings carefully.

QUESTION:-

Q1  What do you mean by RTD?

Q2  Which material is generally used in the construction of RTD?

Q3What are the uses of RTD?

 

 

 

EXPERIMENT NO. 7(b)

OBJECT:- Measurement of temperature using thermistor.

APPARATUS REQUIRED: - Thermistor kit, Heating arrangement, Ice, Thermometer, H2O.

 THEORY: - Thermistors are also called thermal resistors. For thermistor the absolute temperature- resistance relationship is given by

                                    RT=RT1exp [β(1/T1-1/T2)]      

Where RT=Resistance of the thermistor at absolute temperature T

            RT1= Resistance of the thermistor at absolute temperature T1

            β= Constant

            T1 and T2 = Absolute temperatures

Thermistors are made up of semiconductor materials. As temperature changes the resistance of materials also changes. The temperature range for thermistor is –600C to +150C. Its resistance varies from 0.5Ω to 0.75MΩ. Thermistor is placed in contact with the media whose temperature is to be measured. As the temperature of the media changes, the resistance of the thermistor gets changed. This change of resistance can be measured by connecting the thermistor in any one arm of the Wheat stone bridge.

 

CIRCUIT DIAGRAM:-

 

FIG. 7.2- CIRCUIT DIAGRAM OF THERMISTOR

PROCEDURE: -

  1. Connect the main power cord at I/P main socket.
  2. Switch ON the power supply
  3. Connect the thermistor sensor at the pin connector. 
  4. Keep the thermistor in boiling water & adjust the display ranging 100 by the adjustment span knob.

OBSREVATION TABLE:-

S.No

 

Temperature Sensor

                                             

Display Reading (mm)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RESULT:-We have measured temperature using Thermistor. 

PRECAUTIONS:-

 

  1. Handle all equipments with care.
  2. Make connections according to the circuit diagram.
  3. Take the readings carefully.
  4. The connections should be tight.

QUESTIONS:-

Q1 What are the advantages of thermistors?

Q2What are the limitations of thermistors?

Q3 What are the various configurations of thermistors?

  

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