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EEP301: Transducer and instrumentation

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Control Lab experiment EEP301, 5th sem electrical engineering @ IIT Delhi

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EEP301: Transducer and instrumentation

1. 1. EEP301 LAB REPORT TRANSDUCER AND INSTRUMENTATION TRAINER (DIGIAC 1750) SUBMITTED BY: Vivek Mangal (2010EE50566) Umang Gupta (2010EE50564) Mehul Mittal (2010EE50553) Kumar Sourav (2009EE50796) Indra Bhushan (2010EE50548) Aastha Dua (2009EE50052) Akshay Gupta (2009EE50275)
2. 2. Servo-potentiometer Aim: To observe the characteristic of the output voltage/dial setting of servo Potentiometer. Introduction: In a positional Resistance Transducer, the position is observed in terms of resistance. If the resistive element and a contact is arranged in a rotary manner, the resistance change can be related to an angular position of the contact. This arrangement can be obtained by using Servo potentiometer. Observation: The maximum voltage position is achieved when the dial is at 172O Angle(o ) Voltage(V) 172 5 150 4.47 120 3.61 90 2.717 60 1.817 30 0.93 0 0.0211 -30 -0.873 -60 -1.769 -90 -2.666 -120 -3.516 -150 -4.37 -180 -5.02 Graph: Voltage as a function of angular position of the dial. -6 -4 -2 0 2 4 6 -200 -100 0 100 200 Voltage Voltage
3. 3. Wheatstone Bridge Aim: To find out the value of unknown Resistance using Wheatstone bridge. Introduction: A Wheatstone bridge is an electrical circuit used to measure an unknown electrical resistance by balancing two legs of a bridge circuit, one leg of which includes the unknown component. Its operation is similar to the original potentiometer. Wheatstone bridge circuit When Ig = 0, Rx can be measured as: Rx = (R2/R1)*R3 Observation: Zero Setting Dial reading = 202 R3 = 2.02 kOhm R1 = 10 – R3 kOhm = 7.98 kOhm R2 = 12 kOhm 10 kOhm Resistor setting Dial reading R3 = 10*Dial R1 = (10kOhm - R3) Rx 10 484 4840 5160 11256 9 476 4760 5240 10901 8 452 4520 5480 9898 7 422 4220 5780 8761 6 386 3860 6140 7544 5 346 3460 6540 6349 4 294 2940 7060 4997 3 250 2500 7500 4000 2 182 1820 8180 2670 1 90 900 9100 1187
4. 4. Graph: Resistance R4 observed as a function of 10kOhm Resistor Setting Result: Rx comes out to be approximately equal to the resistance applied. The Platinum RTD (Resistance Temperature Dependent) Transducer Aim: To observe the temperature – resistance characteristic in a Platinum RTD Transducer Introduction: In a Platinum RTD, the increase in resistance is linear, the relationship between resistance change and temperature rise being 0.385 Ohm/o C Rt = Ro + 0.385t, Ro=Rt = 100 Ohm at 0o C. Temperature sensor measures the value of temperature in 10mV/o K Observation and Calculation: Platinum RTD voltage recorded = 110 mV Temperature Sensor INT = 3.056 V So, temperature = 305.6 o K = 32.6 o C Calculated RTD resistance = 100 + 0.385*(o C) = 100 + 0.385 * 32.6 = 112.55 Ohm 0 2000 4000 6000 8000 10000 12000 0 2 4 6 8 10 12 Resistance Rx R4
5. 5. NTC (Negative temperature coefficient) Thermistor Aim: To observe the temperature-resistance characteristic of a Negative Temperature Coefficient Thermistor. Introduction: In an NTC Thermistor, resistance decrease with increase in temperature. Thermistor differ from RTD as the material used in a Thermistor is generally a ceramic or polymer, while RTD uses pure metals. RTDs are useful over larger temperature ranges, while thermistors typically achieve a higher precision within a limited temperature range, typically −90 °C to 130 °C. Observation: Thermistor resistance = 10*Dial reading + 1 kOhm Time(min.) Temperature (INT reading) Temperature (K) Temperature (C) Dial reading Thermistor Resistance (Ohm) 0 3.057 305.7 32.7 258 3580 1 3.089 308.9 35.9 234 3340 2 3.134 313.4 40.4 190 2900 3 3.189 318.9 45.9 152 2520 4 3.23 323 50 118 2180 5 3.267 326.7 53.7 100 2000 6 3.299 329.9 56.9 86 1860 7 3.325 332.5 59.5 74 1740 8 3.344 334.4 61.4 64 1640 9 3.361 336.1 63.1 54 1540 10 3.372 337.2 64.2 50 1500 Graph: Thermistor Resistance plotted as a function of Temperature 0 500 1000 1500 2000 2500 3000 3500 4000 25 35 45 55 65 75 Thermistor Resistance(Ohm) Thermistor Resistance(Ohm)
6. 6. Photovoltaic Cell Aim: To observe the short circuit current and open circuit voltage characteristic of a photovoltaic cell. Introduction: A photovoltaic cell can be used either as a current source or a voltage source and is inherently a linear device. When used as energy source, these photovoltaic cells are known as Solar Cells. Observation: Lamp filament Voltage Short Circuit Current (uA) Open Circuit Voltage (V) 1 0 0 2 0 0.6 3 2.6 2.25 4 20.6 3.56 5 69.9 4.9 6 164.8 6.32 7 324.3 7.78 8 606 9.16 9 802 10.13 10 803 10.16 Graph: Short Circuit Output Current as a Function of Lamp Filament Voltage The graph is approximately linear after some appropriate voltage is applied. -100 0 100 200 300 400 500 600 700 800 900 0 2 4 6 8 10 12 Current (uA) Current (uA)
7. 7. Graph: Open Circuit Voltage as a Function of Lamp Filament Voltage Result: The open circuit voltage as well as short circuit current is observed to have linear dependence on the lamp filament voltage. 0 2 4 6 8 10 12 0 2 4 6 8 10 12 Voltage (V) Voltage (V)
8. 8. Phototransistor Aim: To observe the output voltage characteristic of a Phototransistor as a function of applied lamp filament voltage. Introduction: A phototransistor is in essence a bipolar transistor encased in a transparent case so that light can reach the base-collector junction. When light falls on the base region, the leakage current increases, which flows from the base emitter junction, thus functioning as an amplifier. As the lamp filament voltage increases, current increases, so the voltage drop VCE decreases. VCE = V – I*R Lamp filament voltage Phototransistor output 0 5.01 1 5.01 2 4.95 3 4.52 4 3.315 5 1.226 6 0.842 7 0.816 8 0.8 9 0.788 10 0.781 Graph: Phototransistor Output Voltage as a function of Lamp Filament Voltage 0 1 2 3 4 5 6 0 2 4 6 8 10 Phototransistor output voltage Phototransistor output
9. 9. Photoconductive Cell Aim: To observe the output voltage characteristic of a photoconductive cell as a function of applied lamp filament voltage. Introduction: The photoconductive cell is a two terminal semiconductor device whose terminal resistance vary linearly with the intensity of the incident light. It is frequently called a photo- resistive device. The photoconductive materials most frequently used include cadmium sulphide (CdS) and cadmium selenide (CdSe). Both materials respond rather slowly to changes in light intensity. Observation: Lamp filament voltage Photoconductor output voltage 0 4.92 1 4.92 2 4.87 3 4.46 4 3.603 5 2.576 6 1.821 7 1.28 8 0.949 9 0.732 10 0.604 Graph: Photoconductor output voltage as a function of applied lamp filament voltage. 0 1 2 3 4 5 6 0 2 4 6 8 10 12 Photoconductor output voltage Photoconductor output voltage
10. 10. Strain Gauge Transducer Aim: To observe the output voltage of a strain gauge transducer as a function of load applied. Introduction: A strain guage measures the external force applied to a fine wire. A fine wire is usually arranged in the form of a grid. The pressure change causes a resistance change due to the distortion of the wire. The value of the pressure can be found by measuring the change in resistance of the wire grid. Generally this resistance is observed by using a Wheatstone bridge but in this experiment we observe the output voltage which is linearly dependent on resistance. Observation: No. of Coins Output Voltage 0 0 1 0.769 2 1.389 3 2.108 4 2.76 5 3.38 6 3.98 7 4.64 8 5.32 9 6.35 10 7 Graph: Output Voltage as a function of number of Coins placed. 0 1 2 3 4 5 6 7 8 0 2 4 6 8 10 12 Output Voltage Output Voltage