Thermocouple Experiment


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Electrical Engineering Experiment

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Thermocouple Experiment

  1. 1. 2010 SPARK-KING Knowledge is NO-WHERE ….. (Engineering Lectures and Engineering Solutions) 09833066325 / 08796149007 VIJAY BALU RASKAR BE-Electrical / MBA - Operation [Engineering Assignments]
  2. 2. SPARK-KING ….. Unique solution for Learning. VBR Experiment No: Title: Principle of thermocouple & characteristics of different thermocouple Roll No: Batch: Date: ___________________________________________________ DESIGNED BY, PROF. VIJAY BALU RASKAR
  3. 3. SPARK-KING ….. Unique solution for Learning. VBR EXPERIMENT NO. PRINCIPLE THERMOCOUPLE AND CHARACTERISTICS OF DIFFERENT THERMOCOUPLE TITLE: To understand the principle of thermocouple & to obtain characteristics of different thermocouples. AIM: To plot characteristics of thermocouple and find out non linearity. APPARATUS: Heater, Multimeter, Thermocouple, Water OR Thermocouple Trainer THEORY: A thermocouple consists of a pair of dissimilar metal wires joined together at one end, terminating at the other end, which is maintained at known temperature. In industrial application choice of material used to make up thermocouple depends on the temperature. Temperature should be measured using devices that measure temperature. It is based on see back effect that when two different metals having work junction when placed together, a voltage is generated at the junction. This principle is used to convert heat energy into electrical energy. Thermocouple type instrument can be used for both A.C. and D.C. application. Most attractive feature is that they are used for measurement of voltage current at high frequency. In fact these instruments are very accurate when above 50 Hz. CONSTRUCTION: Thermocouple consists of two dissimilar wires as to form two junctions. One junction is kept at constant and other is heated. Hot junction is called as measuring junction and cold junction is called as reference junction. Thermocouple may be prepared by casting two wires together. Thermocouple conductor must be insulated from hot junction to the indicating instrument. The two wires should not touch each other. Therefore suitable insulating material must be used accordingly. Temperature ranges for insulating: 1. Enameled and cotton : 250 0 F 2. Glass and asbestos : 900 0 F 3. Ceramic : 2600 0 F ___________________________________________________ DESIGNED BY, PROF. VIJAY BALU RASKAR
  4. 4. SPARK-KING ….. Unique solution for Learning. VBR On the basis of the thermoelectric principle of the thermocouple, the material decided into and base type material. Thermocouple doesn’t use rare conductors except in application where atmospheric condition permits the leads and junctions are internally insulated from sheet using various plotting component. They are normally installed in particular walls so that they may easily be removed or replaced without interaction and shut down plan. PRINCIPLE: Device that measured temperature on the basis of thermoelectric principle is called as thermocouple. The thermocouple principle given below on emf generated across the junction of dissimilar metal when junction is heated. 1. See back effect: If close circuit are formed by two dissimilar metals at different temperatures then current flow from hot junction produces a proportional voltage at the junction. 2. Peltier effect: When loop was formed by two dissimilar metals and if externally current was forced to flow through one junction of bridge is heated cold junction. 3. Thomson’s effect: When current flowing through copper wire whose temperature vary from point heat when current at any direction is in same direction of current flow. While heat is absorbed at point if current in opposite direction of heat flow.. WORKING: Since, thermocouple emf depends upon the difference in temperature eat junction the temperature of water should remain absolutely constant in order to calibrate thermocouple to reduce errors due to change in ambient temperature. Reference temperature should be kept at 00 C and thermocouple can be used up to 14000 C. ADVANTAGES: 1. Cheaper than RTD. 2. Good reproducibility 3. Speed of response is high 4. Accuracy is high 5. Rugged construction DISADVANTAGES: 1. Cold junction and lead compensation is required 2. Needs signal amplification 3. Exhibits non linearity PROCEDURE:  Ensure the following points – ___________________________________________________ DESIGNED BY, PROF. VIJAY BALU RASKAR
  5. 5. SPARK-KING ….. Unique solution for Learning. VBR o Main supply is single phase. o Furnace is off and sensor is in place. o Fan is off and away from furnace. o Sensor under calibration is removed from furnace. o The set point at temperature controller is set below 900C 1. Put water inside the tank in appropriate level. 2. Insert sensor in the furnace (K-Type or PT-100) 3. Connect multimeter at PT-100 (ohm) 4. Connect multimeter at K-type (mV) 5. Connect trainer to main power supply. 6. Noted down all the readings in different interval of time. NOTE:-  J/K Thermocouple Sensor:- Set point – strictly up to 900C  RTD PT 100 Sensor: Set point – strictly up to 500C OBSERVATION TABLE: Sr. Furnace Temperature (C ) J T/C output (mV) PT – 100 (Ohm) No. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. ___________________________________________________ DESIGNED BY, PROF. VIJAY BALU RASKAR
  6. 6. SPARK-KING ….. Unique solution for Learning. VBR GRAPH: Draw a Graph for FT VS J T/C Output and FT VS PT-100 CALCULATION: RC  100  0.385T Where, RC  Resistance at temperature T (C ) T = Temerature at 100 (C ) The increase in resistance is linear, the relationship between resistance changesand temperature rise being 0.385 Ω /°C RESULT:- We calculated the resistance at Temperature and also find the thermocouple output by using multimeter. For, _______ (C ) we get _____ mV and ______ohm CONCLUSION: Thus, we have studied construction and working of thermocouple and determined its sensitivity and linearity. ___________________________________________________ DESIGNED BY, PROF. VIJAY BALU RASKAR
  7. 7. SPARK-KING ….. Unique solution for Learning. VBR CIRCUIT DIAGRAM:- ___________________________________________________ DESIGNED BY, PROF. VIJAY BALU RASKAR