Network and Measurement

Dev Bhoomi Institute Of Technology LABORATORY Department of Electrical & Electronics Engg. MANUAL PRACTICAL INSTRUCTION SHEET EXPERIMENT NO. ISSUE NO. : ISSUE DATE: 10-July-2010 REV. NO. : REV. DATE : PAGE: 1

LABORATORY Name & Code: NETWORK & MEASUREMENT LAB SEMESTER: III (PEE353)

MEASUREMENT LAB

1. Study of semiconductor diode voltmeter and its use as DC average responding AC voltmeter.

2. Study of L.C.R bridge & determination of the value of the given components.

3. Study of distortion factor meter & determination of the % distortion of the given oscillator.

4. Study of the following transducer (i) K- type trans (ii) Pressure trans

5. Measurement of phase difference & frequency using CRO (Lissajous figure)

6. Measurement of the resistance using Kelvin’s double bridge.

7. Study of the transistor tester and determination of the parameters of the given transistors.

8. To study the process of 4-bit analog to digital conversion by counter method.

9. To study the process of 4-bit digital to analog conversion by counter method.

10. To Study Super heterodyne AM receiver and measurement of receiver parameters viz. sensitivity,

selectivity & fidelity.

Prepared By- Mr Pawan Negi Approved By- Mr. Rohit Kumar

LABORATORY Name & Code: NETWORK & MEASUREMENT LAB SEMESTER: III (PEE353)

EXPERIMENT - 1

1. AIM: Study of semiconductor diode voltmeter and its use as DC average responding voltmeter.

2. APPARATUS REQUIRED:

S. No Component name Specification Qty 1. Function Generator 2. DMM 3. Patch cords

3. THEORY:

The conventional voltmeter based upon a moving coil movement responds to a DC signal. To use dc voltmeter as an ac voltmeter diode rectifiers are employed. An AC signal can be converted into a unidirectional signal by passing it through a rectifier diode. Here the diode conducts during the positive half cycle of the signal, but presents a high impedance path to negative cycle. The output signal has series of positive half cycles, which can be used to deflect dc voltmeter. The meter movement is unable to respond to the rapidly changing signal, gives a reading which is proportional to the average value of the input signal over a period of time. The average value of half rectified sine wave pulses:

Vavg = (Vpk/π)

Which is 1/3 of the peak amplitude. The improved output of rectifier may obtained by using diode rectifiers in bridge configuration. The bridge rectifier converts both half cycles to dc, gives an average dc output to ac input is -

Vavg = 2(Vpk/π)

It is twice of half wave rectifier output. The input ac sinusoidal voltage is measured in rms & the output dc is averaged having a ratio, called form factor. The series resistance of bridge rectifier can be adjusted to take rms readings.

Prepared By- Mr Pawan Negi Approved By- Mr. Rohit Kumar

LABORATORY Name & Code: NETWORK & MEASUREMENT LAB SEMESTER: III (PEE353)

BLOCK DIAGRAM OF DMM

4. PROCEDURE:

1. Take reading across resistor using DMM for any type of voltage or current input.

2. Connect the function generator with the ac input sockets, select sine wave at 100 Hz frequency. Kept the switch to ON position.

3. Connect DMM (ac 20V range) across the function generator & note the readings in rms.

4. Put the given to off position. Note the voltmeter reading as Vavg. 5. Select switch to ON position. Decrease the amplitude control to read 2V. Note the reading of DMM.

6. Select switch position to off stage. Note Vavg.

7. Take such readings for 1V & 0.5V (switch is in ON state), & note DMM readings. Compare the result, which clearly show the inaccuracy in dial readings in lower ac voltage measurements.

Prepared By- Mr Pawan Negi Approved By- Mr. Rohit Kumar

LABORATORY Name & Code: NETWORK & MEASUREMENT LAB SEMESTER: III (PEE353)

8. From the results plot a curve between the input & o/p (voltmeter reading), which is a straight line.

The average o/p:

Vavg = Vrms/1.11

Where Vrms is DMM reading & Vavg is voltmeter reading taken at switch off.

5. OBSERVATION:

S.No Voltmeter Voltmeter DMM Reading, Vrms Reading, reading, (SW ON) Vavg Vrms (SW OFF) (i/p) 1, 2. 3. 4.

6. CALCULATION: Complete table with graph representation.

7. RESULTS: Thus determine I/p – o/p characteristics of rectifier voltmeter.

Prepared By- Mr Pawan Negi Approved By- Mr. Rohit Kumar

LABORATORY Name & Code: NETWORK & MEASUREMENT LAB SEMESTER: III (PEE353)

EXPERIMENT 2

1. AIM: Study of L.C.R bridge & determination of the value of the given components.

2. APPARATUS REQUIRED:

S.no Component name Specification Qty 1. Capacitor <1uF 2. Capacitor (Non >1uF Electrolytic) 3. Capacitor >1uF (Electrolytic) 4. Inductor < 1H 5. Inductor >1H 6. Resistor < 10 K ohms 7. Resistor >10 K ohms

3. THEORY:

The LCR Q Bridge measures inductance, capacitance, resistance & Q with a basic accuracy of ± 0.25% of reading for values up to 2000 H 2000 F & 99 respectively, either series equivalent or parallel equivalent component values are displayed. LCR-Q bridge is auto ranging it selects range automatically & also it discriminates automatically between inductors & capacitors. Frequencies of measurements is 100Hz or 1 KHz . An internal DC bias voltage of 2 volt can be selected for use when testing electrolytic capacitors.

4. PROCEDURE:

1. Frequency Test Prompts :

Capacitors in range 3nF to 2000uF, & inductor in range 2mH to 2000 H, can be measured, to the basic accuracy at a measurement frequency of 100 Hz. If an attempt is made to measure components in these range, at a frequency which prevent the basic accuracy from being attained, a frequency change will be indicated by flashing the frequency indicator LED. Thus LCR-Q bridge will provide a measurement at inappropriate frequency, but the basic accuracy may not be achieved.

Prepared By- Mr Pawan Negi Approved By- Mr. Rohit Kumar

LABORATORY Name & Code: NETWORK & MEASUREMENT LAB SEMESTER: III (PEE353)

2. Measurement Conditions:

LCR-Q is capable of providing both series & parallel equivalent values of components, at frequencies of 100 Hz & 1 kHz. This is to achieve measurements which have the most relevance either to the physical form of the component or to a manner in which is commonly used. This is for a number of reasons associated with the physical construction of this type of component. Their value at 100 Hz is the most useful, therefore. The loss term of such capacitors isexpressed as Equivalent Series Resistance (ESR), series capacitance & resistance values should be measured.

5. CALCULATION:

1. Note the value of C, Vc, V2. 2. Q is calculated as Q = VcVe3. 3. L can be estimated using three relations: f = 1/2п√LC f² = 1/4П²LC L =1/4п²FC

6. ASSUMPTIONS:

1. Internal impedance of voltage source is neglected. 2. The capacitor is assumed to be non leaky. 3. Inverting capacitance is neglected.

8. RESULTS AND DISCUSSION: Measured Q is less than actual Q.

Prepared By- Mr Pawan Negi Approved By- Mr. Rohit Kumar

LABORATORY Name & Code: NETWORK & MEASUREMENT LAB SEMESTER: III (PEE353)

EXPERIMENT- 3

1. AIM: Study of distortion factor meter & determination of the % distortion of the given oscillator.

2. APPARATUS REQUIRED:

S. No Component name Specification Qty 1. Distortion factor 1 meter 2. Function generator 1 3. Connecting wires.

3. THEORY:

When a sinusoidal signal is applied to an amplifier it produces sinusoidal output. However in most of cases the output is not exact replica of input because of the nonlinear of active device. The amount by which output waveform of an amplifier differs from that of input waveform to measure distortion. If B1 is fundamental, B2 is amplitude of Ist harmonic

nd Distortion of 2 harmonic D = B2 / B1

rd Distortion of 3 harmonic D = B3 / B1

Where D = distortion of nth harmonic

Total harmonic distortion D = (D2 +D3 +D4 ...... +Dn )

The parallel resonant circuit consist of Lp, Rp and Cp is to provide compensation for the variation in the ac resistance of the series resonant circuit consisting of inductor L & capacitor C and also for the variation in the amplifier gain over the frequency range of the instrument.

Prepared By- Mr Pawan Negi Approved By- Mr. Rohit Kumar

LABORATORY Name & Code: NETWORK & MEASUREMENT LAB SEMESTER: III (PEE353)

The output of the series resonance circuit is transformer coupled to the input of an amplifier the output of the amplifier is rectified and applied to a meter circuit. Series resonant circuit is tuned to specific Harmonic frequency. CIRCUIT DIAGRAM:

4. PROCEDURE:

a) Connect the input signal from function generator to distortion meter.

b) Take the various signals, first sat calibration and see the distortion on 100% scale.

c) Note the distortion for different waves.

Prepared By- Mr Pawan Negi Approved By- Mr. Rohit Kumar

LABORATORY Name & Code: NETWORK & MEASUREMENT LAB SEMESTER: III (PEE353)

5. OBSERVATION:

Distortion and type of waveform for different input given -

S. No. Frequency Type of waveform Distortion

6. RESULTS AND DISCUSSION:

Distortion for sine wave is minimum approximately 2-3% for triangular wave 11-12% and maximum for square wave 42-44%

7. PRECAUTIONS:

a) All connection should be according to the circuit diagram.

b) All connection should be right & tight.

c) Reading should be taken carefully.

d) Power supply switched off after completing the experiment.

Prepared By- Mr Pawan Negi Approved By- Mr. Rohit Kumar

LABORATORY Name & Code: NETWORK & MEASUREMENT LAB SEMESTER: III (PEE353)

EXPERIMENT 4

1. AIM: Study of the Pressure Cell transducer.

2. APPARATUS REQUIRED:

S.No Component name Specification Qty

1. Pressure cell

2. Digital Multimeter

3. Patch cords

3. THEORY:

Pressure Cell: A pressure cell is an electromechanical device which converts applied pressure into an electrical signal & is used for measurement of static & dynamic forces. The pressure cell has a receiving element having highly tensile strength & strain gauges which convert this change in formation of pressure receiving element into proportional change in electrical signal. Pressure cell has three basic parts, the housing, the receiving element (diaphragm, disc) & strain gauges. In the pressure cell four strain gauges are mounted to form four arm active bridge. The bridge is excited with a dc potential obtained from a band gap reference.

4. PROCEDURE:

1. Connect the given pressure cell with the set up by mean of 5 pin connector. Switch ON the power. The readout will glow.

2. Set zero control to made readout 00.0

3. Apply known pressure 50Psi, upon the cell by mean of pressure applying column handle clockwise

Prepared By- Mr Pawan Negi Approved By- Mr. Rohit Kumar

LABORATORY Name & Code: NETWORK & MEASUREMENT LAB SEMESTER: III (PEE353) rotation & read Bourden gauge.

4. Adjust the span control to read the o/p display as 50 Psi. Rotate the handle of pressure applying column reverse direction to read 0 at Bourden gauge, the readjust zero control for 00.0 readout. Put the same pressure again & adjust readout for 50Psi.

5. Bring back pressure to zero, if required adjust zero by zero adjust.

Measurement:

1. Connect multimeter across the analog output. Apply same pressure (25 Psi) on the cell. Note the displayed psi from panel meter & analog voltage Van, from multimeter.

2. Connect multimeter at instrumentation amplifier output(socket marked A) note voltage as Vin.

3. Apply pressure in same steps up to 100Psi & note the readings.

6. OBSERVATION:

P(psi) Vin, mV Van, volt Psi/display 0 25 50 75.

7. CALCULATION:

Є = V/ (GF . Vr)

∆V = Van/Av

Є = 2[ (Van/Av) / (Gf.Vr)]

Av’ = ∆Van / ∆Vin Where Av is amplifiers voltage gains given as Av = A1.A2.A3…

Prepared By- Mr Pawan Negi Approved By- Mr. Rohit Kumar

LABORATORY Name & Code: NETWORK & MEASUREMENT LAB SEMESTER: III (PEE353) Є = strain

Instrumentation Amplifier gain = 75 Av = 75. Av’ 1. Plot a curve b/w strain and pressure. The curve will be a straight line, which verify that strain is proportional to applied pressure.

2. Plot curve between P & displayed value. It should be linear.

8. RESULTS AND DISCUSSION:

Hence we have studied pressure cell transducer.

9. PRE- EXPERIMENT:

1. Define Transducer.

2. Give types of transducer.

3. Differentiate between transducer & sensor.

4. Explain Strain Gauge in detail.

Prepared By- Mr Pawan Negi Approved By- Mr. Rohit Kumar

LABORATORY Name & Code: NETWORK & MEASUREMENT LAB SEMESTER: III (PEE353)

EXPERIMENT 5

1. AIM: Measurement of phase difference & frequency using CRO (Lissajous figure).

2. APPARATUS REQUIRED:

S.no Component name Specification Qty 1. CRO 1 2. Signal Generator 1

3. Patch Cords 3

3. THEORY:

1.1 Measurement of Voltage Using CRO:

A voltage can be measured by noting the Y deflection produced by the voltage; using this deflection in conjunction with the Y-gain setting, the voltage can be calculated as follows :

V = (No. of boxes in cm.) x (selected Volts/cm scale)

1.2 Measurement of Current and Resistance Using a CRO:

Using the general method, a correctly calibrated CRO can be used in conjunction with a known value of resistance R to determine the current I flowing through the resistor.

1.3 Measurement of Frequency Using a CRO:

A simple method of determining the frequency of a signal is to estimate its periodic time from the trace on the screen of a CRT. However this method has limited accuracy, and should only be used where other methods are not available. To calculate the frequency of the observed signal, one has to measure the period, i.e. the time taken for 1 complete cycle, using the calibrated sweep scale. The period could be calculated by

Prepared By- Mr Pawan Negi Approved By- Mr. Rohit Kumar

LABORATORY Name & Code: NETWORK & MEASUREMENT LAB SEMESTER: III (PEE353)

T = (no. of squares in cm) x (selected Time/cm scale)

Once the period T is known, the frequency is given by f (Hz) = 1/T (sec)

4. Measurement of Phase:

The calibrated time scales can be used to calculate the phase shift between two sinusoidal signals of the same frequency. If a dual trace or beam CRO is available to display the two signals simultaneously ( one of the signals is used for synchronization), both of the signals will appear in proper time perspective and the amount of time difference between the waveforms can be measured.

Figure. Phase shift between two signals

Referring to figure, the phase shift can be calculated by the formula -

Phase shift in cm. One x 360 period in cm.

Prepared By- Mr Pawan Negi Approved By- Mr. Rohit Kumar

LABORATORY Name & Code: NETWORK & MEASUREMENT LAB SEMESTER: III (PEE353)

The frequency relationship between the horizontal and vertical inputs is given by;

y(cm.) Y

Y 1 1 x(cm.) 1 X1 X2

f No. of tangencies (vertical) h = fv No. of tangencies (horizontal)

5. PROCEDURE: The Lissajous pattern shown in figure1 is observed on the CRT screen. Find the phase shift between the signals applied to the X and Y inputs of the scope.

Two sinusoidal inputs having the same amplitudes but different period, are applied to the X and Y inputs of the CRO. Draw the Lissajous pattern which will be observed on the CRT.

The signals given V1 and V2 are applied to the X and Y inputs of the scope. Sketch the Lissajous pattern and calculate the phase difference between the two signals.

V1 = 10 Sin (wt) V2 = 15 Sin (wt + 180)

Prepared By- Mr Pawan Negi Approved By- Mr. Rohit Kumar

Dev Bhoomi Institute Of Technology LABORATORY Department of Electrical & Electronics Engg. MANUAL PRACTICAL INSTRUCTION SHEET

EXPERIMENT NO. ISSUE NO. : ISSUE DATE: 10-July-2010 Figure shows a LissajousREV. pattern NO. observed: on the CRTREV. screen. DATE Determine : the frequencyPAGE: relationship 16 between the signals applied to the X and Y inputs of the scope. LABORATORY Name & Code: NETWORK & MEASUREMENT LAB SEMESTER: III

(PEE353)Fy/Fx = 3/2

FY = (3/2) Fx

If Fx is 100 Hz than Fy = 150 Hz

6. OBSERVATION: The output of CRO is traced with the help of tracing paper.

7. RESULTS:

Hence measurement of phase & frequency has been done & o/p is traced using CRO.

Prepared By- Mr Pawan Negi Approved By- Mr. Rohit Kumar

LABORATORY Name & Code: NETWORK & MEASUREMENT LAB SEMESTER: III (PEE353)

EXPERIMENT 6

1. AIM: Measurement of the resistance using Kelvin’s double bridge.

2. APPARATUS REQUIRED:

S. No Component name Specification Qty 1. Galvanometer

2. Multimeter

3. Resistance 4. Patch cords

3. THEORY: The Kelvin Bridge is a modification of the Wheatstone bridge & provides greatly increased accuracy in the measurement of low- value resistances, generally below 1 ohm. The double bridge is used because the circuit contains a second set of ratio arms, which is connected to the galvanometer. The Kelvin bridge is used for measuring very low resistances (1 ohm to low as 0.00001 ohm). In this bridge, resistance is represented by the variable standard resistor. The ratio of arms(R1 & R2) can be usually be switched in a number of decade steps. Contact potential drops in the measuring circuit may cause large errors & to reduce this effect the standard resistor consists of nine steps of 0.001 ohm each plus a calibrated manganin bar of 0.0011 ohm with a sliding contact.

4. CIRCUIT OF KELVIN DOUBLE BRIDGE

Prepared By- Mr Pawan Negi Approved By- Mr. Rohit Kumar

LABORATORY Name & Code: NETWORK & MEASUREMENT LAB SEMESTER: III (PEE353)

5. PROCEDURE:

Application: Measurement of low resistance from 0.2 micro Ω to 11 Lay Out:  Main Dial: It consists of 10 coils of 0.01 Ω.

 Slide Wire: It also of 0.01 ohm, divided into 500 equal parts.(least count of each small division =0.00002 ohm).

 Multiplying Ratio: A single dial having ratios of 0.01, 0.1, 1,10 & 100 ohms.

 Current Reversing Switch: It is to reverse the direction of current & to switch off the battery circuit to the KELVIN’S BRIDGE>

 Terminals: Eight terminals are fitted on the panel. Two terminals are marked D.C. meant for  D.C source connected to the KELVIN BRIDGE. Two terminals are marked GALVO meant null detector to be connected. Four terminals on the left side of the panel are meant for unknown resistance.

Measurement of Two Terminal Resistance.

 Connect the potential terminals of the Kelvin bridge to the resistance terminals.

 Connect the current terminals of the Kelvin bridge to the resistance terminal.

1. CALCULATION:

Ekl = ( R2/R1 + R2 ) E =( R2/R1 + R2 ) I

Rx=R3(R1 / R2)

7. RESULTS: Hence resistance has been measured using Kelvin double bridge.

Prepared By- Mr Pawan Negi Approved By- Mr. Rohit Kumar

LABORATORY Name & Code: MEASUREMENT LAB (PEE353) SEMESTER: III

EXPERIMENT- 7

1. AIM: Study of the transistor tester and determination of the parameters of the given transistor.

2. THEORY:

Here is a very simple circuit that can be used to check the hfe of transistors. Both PNP and NPN transistors can be checked using this circuit. Hfe as high as 1000 can be measured by using this circuit. The circuit is based on two constant current sources build around transistors Q1 and Q2.The Q1 is a PNP transistor and the constant current flows in the emitter lead. The value of constant current can be given by the equation; (V D1 -0.6)/ (R2+R4).The POT R4 can be adjusted to get a constant current of 10uA.

The Q2 is an NPN transistor and the constant current flows into the collector lead. The value of this constant current can be given by the equation; (VD2-0.6)/(R3+R5).The POT R5 can be adjusted to get a constant current of 10uA.This constant current provided by the Q1 circuit if the transistor under test is an NPN transistor and by Q2 circuit if the transistor under test is a PNP transistor is fed to the base of transistor under test. This current multiplied by the hfe flows in the collector of the transistor and it will be indicated by the meter. The meter can be directly calibrated to read the hfe of the transistor.

3. CIRCUIT:

Prepared By- Mr Pawan Negi Approved By- Mr. Rohit Dobriyal

LABORATORY Name & Code: MEASUREMENT LAB (PEE353) SEMESTER: III

Notes.

 Assemble the circuit on a general purpose PCB.  The circuit can be powered from a general purpose PCB.  J1 and J2 are transistor sockets.  The Zener diodes must be rated at least 400mW.

Simple Transistor Tester

Simple transistor tester is a transistor analyzer circuit which is suitable for testing both NPN and PNP transistors. This is a very simple circuit as compared to other transistor testers. This circuit is very useful for both technicians and students. This circuit can be easily assembled on a general purpose PCB. A basic electronic component like resistors, LED’s, diode and transformer is used for developing this circuit. Using this circuit, we can check whether a transistor is in good condition or not, is it opened or shorted, and so on.

4. WORKING:

The principle behind this circuit is very simple. This circuit basically works on the basis of transistor switching action (Basic Transistor Theory). Take a look at the circuit diagram given below.

Prepared By- Mr Pawan Negi Approved By- Mr. Rohit Dobriyal

LABORATORY Name & Code: MEASUREMENT LAB (PEE353) SEMESTER: III

Testing of NPN Transistor

 Let us start by connecting an NPN transistor to the circuit with the corresponding Emitter, Base, and Collector terminals and the switch on the circuit.  During the first half cycle of the transformer input , the emitter base junction of transistor is forward biased and collector base junction is reverse biased and the transistor is in ON state and diode D1 is in forward

biased The current starts flow through the D1 and the red LED begins to glow. During the next half cycle, the transistor is reverse biased and is in OFF state.

 By the alternative nature of the input AC , we can see that the red LED is in ON state and the transistor is in good working condition(Diode D2 and Green Led is in reverse biased and in OFF state). By using the variable resistor, we can check the transistor with various base currents.  If the NPN transistor is in open state, the transistor does not conduct and no current flow through LED. If the transistor is in shorted condition, the transistor acts as a closed switch. And both diode conduct alternatively and both LED’s starts glowing.

Testing of PNP transistor

The PNP transistor is attached to the device with corresponding pin terminals and switch on the circuit. If, during one half cycle of the input AC (assume top terminal of transformer is negative and bottom is positive), the emitter base and collector base junctions of the transistor are forward biased. Then, in such a condition if there is a and a current flow through the Diode D2 and the Green LED starts glowing, then understand that the transistor is in good working condition(the Diode D1 and Red LED is in reverse biased and not working at that time). During the next half cycle both diodes, and transistors are reverse biased and in OFF state. By the alternating property of input AC, we feel the Green LED is in ON state. We can check this circuit by providing various base currents (by very the variable resistor.

If the PNP transistor is in open state, it doesn’t conduct in both half cycles and no output is obtained. If the transistor is in a shorted condition, transistor acts as a closed path and both diodes are forward biased alternatively, thus making the two LED’s glow at the same time.

5. RESULT:

NPN and PNP Transistor are identified.

Prepared By- Mr Pawan Negi Approved By- Mr. Rohit Dobriyal

LABORATORY Name & Code: MEASUREMENT LAB (PEE353) SEMESTER: III

EXPERIMENT NO.8

1. AIM: To study the process of 4-bit analog to digital conversion by counter method .

2. APPRATUS REQUIRED:

 A/D Converter kit.  Connecting wires.

3. THEORY:

A/D Comparator are the power inter phase b/w digital and analog words ADC in values transition of analog information in to equivalent digital information(word), there are so many connection techniques in given band counter method is adopted. The band layout designed is blocks verify the whole process which is described as follows.

(A)Comparator-: Its basic function is to compare I/p analog voltage in) with the binary ladder o/p voltage ( reference) o/p signal to reset the gate flip-flop.

(B)Flip-flop_-:It is RS flip-flop which is called gate flip-flop. its instruction is to make count gate enables and disable, where it is set applying start signal. Its o/p goes logic 1 which allows count gate to pass I/P clock signal to the up-counter.

(C)Up counter-: It is a 4- bit counter the o/p of which is a digital equivalent of analog I/P initiated by start pluse.

(D)Binary ladder and switched-: There are the scent of 4- bit digital to analog converter. the up-counter signal switch guard analog switches b/w applied reference and and ground which produce the resultant o o/p is the form of reference o/p to the comparator.

(E)Start and set mono- flops-: There are set of two mono – flops used to set the count gate flip-flop and to reset the counter.

Prepared By- Mr Pawan Negi Approved By- Mr. Rohit Dobriyal

LABORATORY Name & Code: MEASUREMENT LAB (PEE353) SEMESTER: III

4. CIRCUIT DIAGRAM:

5. PROCEDURE ANALOG TO DIGITAL CONVERTOR:

1. Connect the given voltmeter across the analog voltage sockets and adjust input voltage to 1.00 volt with the given knob situated just under the voltmeter note the comparator status LED comes on disconnect the voltmeter from the analog input sockets and connect it with the ref –in socket.

2. Apply a brief push on start key. It will start the conversion which is indicated by another two LEDs fitted with the gate.

3. Note the data output LEDs fitted at the top of the board. Also check the change of voltage in analog meter.

Prepared By- Mr Pawan Negi Approved By- Mr. Rohit Dobriyal

LABORATORY Name & Code: MEASUREMENT LAB (PEE353) SEMESTER: III

6. OBSERVATION TABLE:

ANALOG INPUT (VOLT) REFERENCE VOLTAG OUT PUT VOLTAGE

2. RESULT:

Studied the 4-bit analog to digital converter is verified.

8. PRECAUTION:

(1).Switch off the power supply when not in use.

(2).All the connections should be right and tight.

(3)Reading Should be taken carefully .

Prepared By- Mr Pawan Negi Approved By- Mr. Rohit Dobriyal

LABORATORY Name & Code: MEASUREMENT LAB (PEE353) SEMESTER: III

EXPERIMENT NO.09

1. AIM: To study a 4- bit R-2-R Ladder digital to analog converter.

2. APPRATUS REQUIRED:-

 Experimental board on 8-bit R- 2R Digital to analog converter.  Digital voltmeter range 0-20 volt.

3. THEORY:

A circuit which can convert a binary number in to a corresponding voltage/current is called D to A converter( D/A or DAC).the input to a DAC will be a N-bit digital word and its output is an analog voltage or current. The various o/p in a DAC are in terms of a full- scale o/p voltage V0 (Fs) .the highest of 4-bit word is 1111and the number next to this is 10000.The o/p voltage corresponding to the LSB input(…………….001) is V0 (LSB).similarly for MSB input ( 10000……..) it is Vo ( MSB) and for max input ( 1111…….) it is vo (max)

V0( LSB) = VO(Fs)/1

V0( MSB) = VO(Fs)/2

V (max)= V0(Fs)-V0(LSB)

If V0 (Fs)= 10V

V0(LSB)= 10/16= 0.625 Volt

Vo(MSB)= 10/2= 5 volt

V(max)= 10-0.625 =9.375

The methods of D to A conversion are based on generating current proportional to the positional value of a bit in the binary word. If the bit is high the current is allowed to flow and if the bit is low –then the current is dissolved.

Prepared By- Mr Pawan Negi Approved By- Mr. Rohit Dobriyal

LABORATORY Name & Code: MEASUREMENT LAB (PEE353) SEMESTER: III

4. CIRCUIT DIAGRAM:

5. PROCEDURE 4- BIT R-2R DIGITAL-TO-ANALOG CONVERTOR:

1. Switch on the supply and adjust the VREF= 10volt.

2. Connect VREF to T5 and digital voltmeter 0—20, volt between T5 –T6. 3.4-bit R-2R network with VREF=10 volt.

4.Now measure the voltage for each binary from 0000 to 1111 and verify the eqs.(1) to (3). You will find that the voltage 0.625 volt is added for each next binary digit.

5.Find out V0( LSB), V0(MSB) and V (max) theoretically and compare the results obtained practically.

6.Plot the observations for each binary no.and compare it with fig. and set any other value of VREF ( say 10.24 volt) and repeat steps.

Prepared By- Mr Pawan Negi Approved By- Mr. Rohit Dobriyal

LABORATORY Name & Code: MEASUREMENT LAB (PEE353) SEMESTER: III

6. OBSERVATION:

INPUT OUTPUT

7. RESULT-: Studied the 4-bit R-2R Ladder digital to analog converter

Prepared By- Mr Pawan Negi Approved By- Mr. Rohit Dobriyal

LABORATORY Name & Code: MEASUREMENT LAB (PEE353) SEMESTER: III EXPERIMENT No.10

1. AIM: To Study Super heterodyne AM receiver and measurement of receiver parameters viz. sensitivity, selectivity & fidelity.

2. APPARATUS REQUIRED:- (i)C.R.O. (ii) CRO Probe (ii) DSB/SSB Transmitter(ST 2201) and Receiver Trainer (ST 2202)

1. BLOCK DIAGRAM:

Figure: Superhetrodyne Receiver

4. THEORY:-

Prepared By- Mr Pawan Negi Approved By- Mr. Rohit Dobriyal

LABORATORY Name & Code: MEASUREMENT LAB (PEE353) SEMESTER: III

The principle of operation of the superheterodyne receiver depends on the use of heterodyning or frequency mixing. The signal from the antenna is filtered sufficiently at least to reject the image frequency (see below) and possibly amplified. A local oscillator in the receiver produces a sine wave which mixes with that signal, shifting it to a specific intermediate frequency (IF), usually a lower frequency. The IF signal is itself filtered and amplified and possibly processed in additional ways. The demodulator uses the IF signal rather than the original radio frequency to recreate a copy of the original modulation (such as audio). Fig.1. shows the minimum requirements for a single-conversion superheterodyne receiver design. The following essential elements are common to all superhet circuits: a receiving antenna, a tuned stage which may optionally contain amplification (RF amplifier), a variable frequency local oscillator, a frequency mixer, a band pass filter and intermediate frequency (IF) amplifier, and a demodulator plus additional circuitry to amplify or process the original audio signal (or other transmitted information). To receive a radio signal, a suitable antenna is required.

Mixer stage: The signal is then fed into a circuit where it is mixed with a sine wave from a variable frequency oscillator known as the local oscillator (LO). The mixer uses a non-linear component to produce both sum and difference beat frequencies signals, each one containing the modulation contained in the desired signal. The output of the mixer may include the original RF signal at fd, the local oscillator signal at fLO, and the two new frequencies fd+fLO and fd-fLO. The mixer may inadvertently produce additional frequencies such as 3rd- and higher-order intermodulation products. The undesired signals are removed by the IF bandpass filter, leaving only the desired offset IF signal at fIF which contains the original modulation (transmitted information) as the received radio signal had at fd.

Intermediate frequency stage: The stages of an intermediate frequency amplifier are tuned to a particular frequency not dependent on the receiving frequency; this greatly simplifies optimization of the circuit.[6] The IF amplifier (or IF strip) can be made highly selective around its center frequency fIF, whereas achieving such a selectivity at a much higher RF frequency would be much more difficult. By tuning the frequency of the local oscillator fLO, the resulting difference frequency fLO - fd (or fd-fLO when using so- called low-side injection) will be matched to the IF amplifier's frequency fIF for the desired reception frequency fd. One section of the tuning capacitor will thus adjust the local oscillator's frequency fLO to fd + fIF (or. less often, to fd - fIF) while the RF stage is tuned to fd. Engineering the multi-section tuning capacitor (or varactors) and coils to fulfill this condition across the tuning range is known as tracking. Other signals produced by the mixer (such as due to stations at nearby frequencies) can be very well filtered out in the IF stage, giving the superheterodyne receiver its superior performance. However, if fLO is set to fd + fIF , then an incoming radio signal at fLO + fIF will also produce a heterodyne at fIF; this is called the

Prepared By- Mr Pawan Negi Approved By- Mr. Rohit Dobriyal

LABORATORY Name & Code: MEASUREMENT LAB (PEE353) SEMESTER: III

image frequency and must be rejected by the tuned circuits in the RF stage. The image frequency is 2fIF higher (or lower) than fd, so employing a higher IF frequency fIF increases the receiver's image rejection without requiring additional selectivity in the RF stage. Usually the intermediate frequency is lower than the reception frequency fd, but in some modern receivers (e.g. scanners and spectrum analyzers) it is more convenient to first convert an entire band to a much higher intermediate frequency; this eliminates the problem of image rejection. Then a tunable local oscillator and mixer convert that signal to a second much lower intermediate frequency where the selectivity of the receiver is accomplished. In order to avoid interference to receivers, licensing authorities will avoid assigning common IF frequencies to transmitting stations. Standard intermediate frequencies used are 455 kHz for medium-wave AM radio, 10.7 MHz for broadcast FM receivers, 38.9 MHz (Europe) or 45 MHz (US) for television, and 70 MHz for satellite and terrestrial microwave equipment.

Band pass filter: The IF stage includes a filter and/or multiple tuned circuits in order to achieve the desired selectivity. This filtering must therefore have a band pass equal to or less than the frequency spacing between adjacent broadcast channels. Ideally a filter would have a high attenuation to adjacent channels, but maintain a flat response across the desired signal spectrum in order to retain the quality of the received signal. This may be obtained using one or more dual tuned IF transformers or a multi pole ceramic crystal filter.

Demodulation: The received signal is now processed by the demodulator stage where the audio signal (or other baseband signal) is recovered and then further amplified. AM demodulation requires the simple rectification of the RF signal (so-called envelope detection), and a simple RC low pass filter to remove remnants of the intermediate frequency. FM signals may be detected using a discriminator, ratio detector, or phase- locked loop. Continuous wave (morse code) and single sideband signals require a product detector using a so-called beat frequency oscillator, and there are other techniques used for different types of modulation. The resulting audio signal (for instance) is then amplified and drives a loudspeaker. When so-called high-side injection has been used, where the local oscillator is at a higher frequency than the received signal (as is common), then the frequency spectrum of the original signal will be reversed. This must be taken into account by the demodulator (and in the IF filtering) in the case of certain types of modulation such as single sideband.

RECEIVER CHARACTERISTICS: The important characteristics of receivers are sensitivity, selectivity, &fidelity

Prepared By- Mr Pawan Negi Approved By- Mr. Rohit Dobriyal

LABORATORY Name & Code: MEASUREMENT LAB (PEE353) SEMESTER: III

PROCEDURE:-

1. Apply AM signal with 400 Hz modulating frequency and 30% modulation taken from AM generator into Rx input socket. 2. Set the input carrier frequency to suitable value that lies within the AM band (525 KHz - 1600 KHz). Also set signal level to 100mV. 3. Tune the Receiver using tuning control. Also adjust gain potentiometer provided in R.F. amplifier section of ST2202 so as to get unclipped demodulated signal at detector's output (output of audio amplifier). 4. Note the voltage level at receiver's final output stage i.e. audio amplifier's output on CRO (voltage at resonance (Vr)). 5. Now gradually offset the carrier frequency in suitable steps of 5 KHz or 10 KHz below and above the frequency adjusted in step 2 without changing the tuning of receiver while maintaining the input signal level. 6. Now record the signal level at output of audio amplifier for different input carrier frequency, on CRO (i.e. voltage off resonance (Vi)).

RESULT:-

Superhetrodyne receiver has been studied and plot for receiver parameters viz. sensitivity, selectivity and fidelity has been drawn.

PRECAUTIONS:-

1. Do not use open ended wires for connecting to 230 V power supply. 2. Before connecting the power supply plug into socket, ensure power supply should be switched off 3. Ensure all connections should be tight before switching on the power supply. 4. Take the reading carefully.

Prepared By- Mr Pawan Negi Approved By- Mr. Rohit Dobriyal

LABORATORY Name & Code: MEASUREMENT LAB (PEE353) SEMESTER: III

Prepared By- Mr Pawan Negi Approved By- Mr. Rohit Dobriyal

LABORATORY Name & Code: MEASUREMENT LAB (PEE353) SEMESTER: III

Prepared By- Mr Pawan Negi Approved By- Mr. Rohit Dobriyal