REMAINING PARTS OF UNIT 3 EMI/BETL 305

1. ELECTRONIC
INSTRUMENTATION
BY PRASHANT KUMAR

2. SWEEP FREQUENCY GENERATOR
A sweep frequency generator is a type of signal generator that is used
to generate a sinusoidal output.
Such an output will have its frequency automatically varied or swept
between two selected frequencies.
One complete cycle of the frequency variation is called a sweep.
Depending on the design of a particular instrument, either linear or
logarithmic variations can be introduced to the frequency rate.
However, over the entire frequency range of the sweep, the
amplitude of the signal output is designed to remain constant.

3. BLOCK DIAGRAM OF SWEEP FREQ.
GENERATOR

4. WORKING
In the case of electronically tuned models, two frequencies are used. One
will be a constant frequency that is produced by the master oscillator.
The other will be a varying frequency signal, which is produced by another
oscillator, called the voltage controlled oscillator (VCO).
The VCO contains an element whose capacitance depends upon the voltage
applied across it. This element is used to vary the frequency of the
sinusoidal output of the VCO.
A special electronic device called a mixer is then used to combine the
output of the VCO and the output of the master oscillator.
When both the signals are combined, the resulting output will be
sinusoidal, and its frequency will depend on the difference of frequencies
of the output signals of the master oscillator and VCO.
For example, if the master oscillator frequency is fixed at 10.00 MHz and
the variable frequency is varied between 10.01 MHz to 35 MHz, the mixer
will give sinusoidal output whose frequency is swept from 10 KHz to 25
MHz.

5. APPLICATIONS & FEATURES
Sweep-frequency generators are primarily employed for
measurement of responses of amplifiers, filters, and electrical
components over various frequency bands.
The frequency range of a sweep-frequency generator usually extends
over three bands: 0.001 Hz-100
kHz (low frequency to audio), 100 kHz-1,500 MHz (RF range), and 1 -
200 GHz
(microwave range).
Performance of measurement of bandwidth over a wide
frequencyrange with a manually tuned oscillator is a time-consuming
task. With the use of a sweep frequency generator, a sinusoidal signal
that is automatically swept between two chosen frequencies can be
applied to the circuit under test and its response against frequency
can be displayed on an oscilloscope or X-Y recorder.

6. FREQUENCY SYNTHESIZER
GENERATOR

7. FREQUENCY SYNTHESIZER
A frequency synthesizer is an electronic circuit that generates a range of
frequencies from a single reference frequency.
Frequency synthesizers are used in many modern devices such as radio
receivers, televisions, mobile telephones, radiotelephones, walkie-talkies, CB
radios, cable television converter boxes satellite receivers, and GPS systems.
A frequency synthesizer may use the techniques of
frequency multiplication,
frequency division,
direct digital synthesis,
frequency mixing,
and phase-locked loops to generate its frequencies.
The stability and accuracy of the frequency synthesizer's output are related to
the stability and accuracy of its reference frequency input. Consequently,
synthesizers use stable and accurate reference frequencies, such as those
provided by crystal oscillators.

8. The digital PLL frequency synthesizer is possibly the most widely
used form of frequency synthesizer.
As the name digital frequency synthesizer implies, this technique
uses digital technology.
By placing a digital divider in the phase locked loop, the voltage
controlled oscillator, VCO, is able to run at a higher frequency than
that of the phase detector.
This technique enables a programmable divider to be used and this
allows digital control of the frequency of the VCO by changing the
division ratio.

9. FREQUENCY DIVIDER GENERATOR
• Frequency divider is
designed using FLIP FLOP
• FOR USING D FLIP FLIP
OUTPUT Q bar is connected
to D
• BUT IN CASE OF J K FLIP
FLIP J=K=HIGH VOLTAGE
(VCC)=LOGIC 1
• ALL COUNTERS ARE
FREQUENCY DIVIDER
• Output freq of counter is
divided by Mod of counter
• fout=fin/Mod of couter
DIVIDE BY 2 FREQUENCY GENERATOR

10. FREQ GEN USING J K F/F J=K=
HIGH

11. PULSE AND SQUARE WAVE
GENERATOR
The difference between the pulse and square waveform is with respect to
the duty cycle.
The duty cycle is 50% for the square wave.
The duty cycle is defined as the ratio of the average value of the pulse over
one cycle to the peak value of the pulse.
The average value and the peak value are inversely related to the time
duration.
The duty cycle of a pulse waveform varies. It is not 50%.
Very short duration pulses give a low duty cycle.
Pulse generation can supply more power during its ON
DUTY CYCLE=Ton/(Ton+Toff) , Ton =on time duration , Toff =off time

12. PULSE AND SQUARE WAVE
GENERATOR

13. PLEASE NOTE : THE pulse and square wave generator uses same
upper and lower current sources to charge and discharge Ramp
capacitor while schmit trigger generates square wave/Pulse. (working
discussed in Function generator)
Different resistor and control are used to control duty cycle of pulse

14. SOME SIMPLE SQUARE WAVE GENERATOR (SIMPLE IN CASE YOU
CAN’T MEMORISE ABOVE COMPLEX BLOCK DIAGRAM)
ZENER DIODE BASED
TWO LEVEL CLIPPER
GENERATES A
SQARE WAVE FROM
SINOSOIDAL INPUT
Opamp based comparator used
to generate square wave from
any
input(square/triangular/rando
m)

15. AF SIGNAL GENERATOR
IN THIS QUESTION DISCUSS BARK HUSSEIN CRITERIA AND ONE OF THE
OSCILLATOR (HARTLEY/COLPITT/WEIN BRIDGE OSCILLATOR)
AF=audio frequency
Range of AF= 20Hz to 20,000 Hz

16. DIGITAL FREQUENCY METER (UNIT
IV)

17. WORKING
A frequency meter has a small device which converts the sinusoidal voltage of the
frequency into a train of unidirectional pulses.
The frequency of input signal is the displayed count, averaged over a suitable counting
interval out of 0.1, 1.0, or 10 seconds.
These three intervals repeat themselves sequentially. As the ring counting units resets,
these pulses pass through the time-base-gate and then entered into the main gate,
which opens for a certain period of time interval.
The time base gate prevents a divider pulse from opening the main gate during the
display time interval. The main gate acts as a switch when the gate is open, pulses are
allowed to pass.
When the gate is closed, pulses are not allowed to pass that means the flow of pulses
get obstructed. The functioning of the gate is operated by the main-gate flip-flop.
An electronic counter at the gate output that counts the number of pulses passed
through the gate while it was open. As the next divider pulse is received at main gate
flip-flop, the counting interval ends and divider pulses are locked out. The resultant
value displayed on a display screen which has the ring counting units of scale-of-ten
circuits and each unit is coupled to a numeric indicator, which provides the digital
display. As the reset pulse generator is triggered, ring counters get reset automatically
and the same procedure starts again.

18. WORKING RANGE AND
APPLICATION
The range of modern digital frequency meter is between the range
from104 to 109 hertz. The possibility of relative measurement error
ranges between from 10-9 to 10-11 hertz and a sensitivity of 10-2
volt.
Use of Digital Frequency Meter
For testing radio equipment
Measuring the temperature, pressure, and other physical values.
Measuring vibration, strain
Measuring transducers

19. UNIVERSAL COUNTER
3bit UP /Down
counter

20. WORKING
UP Counting
If the UP input and down inputs are 1 and 0 respectively, then the
NAND gates between first flip flop to third flip flop will pass the non
inverted output of FF 0 to the clock input of FF 1. Similarly, Q output
of FF 1 will pass to the clock input of FF 2. Thus the UP /down
counter performs up counting.
DOWN Counting
If the DOWN input and up inputs are 1 and 0 respectively, then the
NAND gates between first flip flop to third flip flop will pass the
inverted output of FF 0 to the clock input of FF 1. Similarly, Q output
of FF 1 will pass to the clock input of FF 2. Thus the UP /down
counter performs down counting.

21. SENSITIVITY OF DIGITAL
MULIMETER/DVM
Sensitivity: Sensitivity of an instrument indicates the capacity of the
instrument to respond truly to the change in the output,
corresponding to the change in the input. For a voltmeter, sensitivity
is referred to as ∆ Vo / ∆ Vin, the ratio of the change in the output to
the change in the input.
If the output voltage changes by few millivolts, the output should also
change by the same amount in the ideal case.

22. RESOLUTION OF DIGITAL
MULIMETER/DVM
Resolution: Resolution is the smallest change in the measured value
to which the instrument can respond. It is the smallest change the
instrument can measure. For example, a 100 V voltmeter may not be
able to measure 100 mV.