EI 1302 TRANSDUCER LABORATORY 0 0 3 100
AIMThe aim of this lab is to train the students in handling the different kinds of transducers like LVDT, Hall effect, Thermocouple etc., which he often meets in his study.
OBJECTIVE
By training the students in the different aspects of transducers, which are magnetic, electrical, mechanical and optical in nature, he becomes a capable and efficient technician.
1. Loading effect of potentiometer.
2. Strain gauge & load cell characteristics.
3. Capacitive transducers.
4. Photoelectric tachometer & Piezoelectric transducers.
5. Hall effect transducers.
6. Characteristics of LVDT.
7. Characteristics of thermocouple, Thermistor and LDR.
8. Step response characteristics of RTD and thermocouple.
9. P/I and I/P converters.
10. Digital transducer – shaft angle encoder.
P = 45 Total = 45
Detailed Syllabus
1. Loading effect on potentiometer
Aim
To study the loading effect on potentiometer circuit.
Objectives
i. To observe the output, input calibration curve using FET voltmeter has the output device.
ii. To observe the output, input characteristic with an voltmeter whose input impedance is finite.
iii. To observe the linearity which decreases with a decrease in the input impedance of the output meter.
Exercise
1. In the potentiometer circuit, displacement is given to the wiper arm and the corresponding output is observed with 2 meters (one is a FET voltmeter and the other is meter with a finite input impedance)
2. For various input displacements, output voltage from the two different meters are recorded and tabulated.
3. Plot the graph output Vs input displacement for both cases.
Equipment
1. Potentiometer – Linear displacement transducer kit – 1 No
2. Regulated power supply – 1 No
3. FET voltmeter, ordinary voltmeter – 1 No
2. Strain guage and load cell characteristics
Aim
To study the characteristics of strain guage and load cell.
Objectives
1. To identify and study the characteristics of strain guage and load cell.
2. To determine the sensitivity of strain guage and load cell.
3. To determine the Young’s modulus and hence the guage factor of the given strain guage.
Exercise
1. Load and Unload the load cell and strain guage.
2. Measure the corresponding voltages during both loading and unloading and plot
the calibration curve.
3. Find the Young’s Modulus and gauge factor from the graph.
Equipment
1. Strain guage and Load cell kit. – 1 No
2. Variable power supply – 1 No
3. Loads for measurement - A set
3. Capacitive Transducers
Aim
To study the operation of capacitive transducers and use it for measurement of
displacement, pressure etc.
Objectives
1. To identify and study the characteristics of capacitive transducer.
2. To operate the capacitive transducer and accurately measure the displacement in of voltage.
3. To determine the sensitivity of capacitive transducer.
Exercise
1. Change in capacitive is observed in terms of output voltage for the given input displacement.
2. Measure the output voltage for various input displacements.
3. Plot output voltage versus input displacement and determine the sensitivity of the capacitive transducer.
Equipment
1. Capacitive transducer – 1 No
2. Regulated power supply – 1 No
4(a) Characteristics of Photoelectric tachometer
Aim
To study the characteristics of photoelectric tachometer using the servo motor speed control trainer kit.
Objective
1. To calculate the number of pulses generated in the photoelectric pick up.
2. To study the variation of speed with the variation of the input voltage.
Exercise
1. Connect the circuit as per instructions given in the manual.
2. Adjust the power supply.
3. Vary the speed of the motor by using rotary potentiometer and note down the readings.
4. Calculate number of pulses generated in the photoelectric pick up.
5. Draw the graph between voltage and speed.
Equipments
1. Speed control trainer kit – 1 No
2. Power supply – 1 No
3. Wires - Some
4. Multimeter – 1 No
4(b) piezoelectric transducer
Aim
To study the characteristics of piezoelectric transducer.
Objective
1. To measure acceleration in both the directions using piezoelectric transducer.
2. To find the voltage sensitivity of the piezoelectric transducer.
3. To find the response of the piezoelectric transducer.
Exercise
1. Generate the vibrations from vibration excitor.
2. Note down the output voltage from the piezoelectric transducer.
3. Tabulate the readings for various frequencies.
4. Plot the response.
Equipment
1. Piezoelectric transducer – 1 No
2. Vibration excitor – 1 No
3. Voltmeter – 1 No
4. Power supply – 1 No
5. Hall effect Transducer
Aim
To study the characteristics of Hall effect transducer.
Objective
1. To determine the positive hall voltage at the bottom of the transducer.
2. To determine the negative hall voltage.
3. To identify and study the characteristics of hall effect transducer.
4. To measure the displacement of a structural element .
Exercise
1. Study the internal configuration of Hall effect IC.
2. Patch the circuit diagram as per patching diagram.
3. Place the north pole of the magnet above the scale and take the reading air gap between hall IC and magnet to output voltage.
4. Place the south pole of the magnet above the scale and take the reading for different distances and plot the graph between air gap voltmeter readings.
Equipments
1. Hall effect characteristics trainer – 1 No
2. Power supply – 1 No
3. Voltmeter – 1 No
6. Characteristics of LVDT
Aim
To study the operation and characteristics of LVDT
Objective
1. To study the displacement of the core from its null position.
2. To study the variation of output voltage with change in displacement.
Exercise
1. Adjust the potentiometer knob present in the LVDT kit to bring the core to Null position (set the output voltage to be ‘0’ volts)
2. Rotate the knob in the positive direction such that the LVDT scale moves in steps of 1cm and measure the corresponding output voltage.
3. Tabulate the readings.
4. Repeat the above procedure for negative displacement.
5. Plot the characteristic curve between displacement and output voltage.
Equipments
1. LVDT trainer kit – 1 No
2. Power supply – 1 No
7(a) Characteristics of Thermocouple
Aim
To determine the characteristics of thermocouple.
Objectives
1. To determine the voltage for corresponding change in temperature.
Exercise
1. Measure the initial temperature and temperature of boiling water (1000C)
2. Calibrate the thermocouple in the hot water and measure the 50C temperature fall in thermocouple.
3. The output voltage is noted for corresponding fall in temperature.
Equipment
1. Thermocouple trainer kit – 1 No
2. Thermocouple – 1 No
3. Voltmeter – 1 No
4. Heater – 1 No
7(b) Characteristics of thermistor
Aim
To determine the characteristics of thermistor
Objectives
To measure the resistance value for the corresponding changes in temperature.
Exercise
1. Measure the initial temperature of water.
2. Take another vessel full of water and boil it to1000C.
3. Note down the readings for every 50C fall of temperature in thermistor, thermometer and output voltage readings.
4. Plot the Thermistor characteristics.
Equipments
1. Thermistor Trainer kit – 1 No
2. Heater – 1 No
3. Thermistor – 1 No
4. Thermometer – 1 No
5. Voltmeter – 1 No
7(c) Characteristics of LDR
Aim
To determine the characteristics of LDR
Objectives
1. To determine the change in resistance for corresponding change in light intensity.
2. To determine the output voltage for corresponding change in voltage.
Exercise
1. The lamp for LDR is selected by using a select switch.
2. Initially the lamp is kept away from LDR.
3. Now the distance is decreased gradually and the corresponding values of voltages and resistances are taken.
4. Repeat the above steps for various positions of lamp.
Equipments
1. Photo conductive trainer kit – 1 No
2. Multimeter – 1 No
3. Connecting wires – 1 No
8. Step response characteristics of RTD and Thermocouple
Aim
To study the step response characteristic of RTD and thermocouple.
Objective
a. To analyse the change in temperature due to change in emf in case of thermocouple.
b. To analyse the change in temperature due to change in resistance in case of RTD.
c. To observe the transients when step input [i.e sudden change in the input] is given.
Exercise
1. Calibrate the RTD and thermocouple at room temperature and 1000C alternatively.
2. Bring down the sensor to room temperature and provide a sudden change of input temperature to boiling point (i.e) 1000C.
3. Start the stop clock and tabulate the time taken for every 50C rise of temperature.
4. Plot the step response for both the sensors.
Equipment
1. Thermocouple and RTD trainer kit – 1 No
2. Thermometer – 1 No
3. Heater – 1 No
4. Thermocouple and RTD sensors – 1 No
5. Voltmeters – 1 No
9. P/I and I/P Converters
Aim
To study the characteristics of P/I and I/P converters.
Objective
1. To convert the given input pressure to corresponding current output using a P/I converter.
2. To convert the given input current to corresponding pressure output using a I/P converter.
Exercise
P/I converter
1. Connect the P/I converter to the pressure source.
2. Set the pressure range to 3-15 psi using the regulator unit.
3. By varying the pressure range note down the values of the current meter.
4. Plot the graph by taking pressure in x-axis and current in y-axis.
I/P converter
1. Connect the I/P converter to pressure source.
2. Set the pressure range to 20psi using the regulator unit.
3. Vary the input current (4-20) mA using potentiometer and note down the reading using ammeter.
4. Note down the value opening (stem position) in % or in mm.
5. Calculate the output pressure using the valve opening.
6. By repeating above steps, tabulate the readings.
7. Plot the graph by taking current in x-axis and pressure in y-axis.
Equipment
1. P/I trainer kit – 1 No
2. I/P trainer kit – 1 No
3. Pressure source – 1 No
4. Control valve etc – 1 No
10. Digital transducer – shaft angle encoder
Aim
To study the operation of shaft angle encoder and use it for measurement of angular position.
Objectives
1. Linear of angular displacements can be converted into digital signal by having digital encoders.
2. Shaft angle encoders can be used for a total angular displacement of 3600.
Exercise
1. The length of the scale of a translational encoder becomes the circumference of circle on a flat disc of a shaft encoder.
2. The scale is scanned radially and a binary 0 or 1 is obtained from each track depending upon angular position of disc.
3. The accuracy depends upon the number of brakes and if there are n tracks the accuracy obtained is 3600 / 2n
Equipments
1. Digital shaft angle encoder – 1 No
2. Regulated power supply – 1 No