ASSIGNMENT-01

ES1107 - ENGINEERING MEASUREMENT AND MACHINES

INSTITUTE OF ENGINEERING AND TECHNOLOGY(IET),

SUBMITTED TO:
Mr. YOGESH ROHILLA

SUBMITTED BY:
KOPPUNOOR BHANU PRAKASH REDDY
2020BTECHCSE041
Question-1 :
What do you mean by Analog to Digital Converter ? Provide at least 2 ways to
convert Analog to Digital.
Solution:
An analog-to-digital converter is any device that converts analog signals into
digital signals. The analogue signal is a continuous sinusoidal waveform that a
computer cannot interpret, necessitating conversion. By converting the analog
signal, data can be amplified, added, or taken from the original signal.
If we have an analog signal, then we want to change an analog signal to digital
data we use two techniques:
1. Pulse code modulation
2. Delta modulation.
After the digital data are created then we convert the digital data to a digital
signal.
Pulse code modulation:
Pulse Code Modulation (PCM) is the most common technique used to change
an analog signal to digital data (digitization). A PCM encoder has three
processes are:
i)Sampling
ii) Quantization
iii) Encoding
Sampling:
The first step in PCM is sampling. The analog signal is sampled every Ts s,
where Ts is the sample interval or period. The inverse of the sampling interval
is called the sampling rate or sampling frequency and denoted by ƒs, Where ,
ƒs = 1/ Ts.
Quantization:
The outcome of sampling is a series of pulses with amplitudes that fall between
the signal's maximum and lowest values. With non-integral values between the
two limits, the set of amplitudes can be infinite. The encoding procedure will
not accept these values.
The following are the steps in quantization:
1. We assume that the original analog signal has instantaneous amplitudes
between Vmin and Vmax
2. We divide the range into L zones, each of height ∆ (delta).
∆=(Vmax-Vmin)/L
3. We assign quantized values of 0 to L - I to the midpoint of each zone.
4. We approximate the value of the sample amplitude to the quantized values.
The quantization value is chosen from the centre of each zone via the
quantization procedure. This indicates that the normalised quantized values and
the normalised amplitudes are not the same. The difference between the two is
known as the normalised error. Based on the quantization levels to the left of
the graph, the fourth row is the quantization code for each sample. The encoded
words are the conversion's ultimate products.
Encoding:
Encoding is the final stage of PCM. Each sample may be converted to a nb-bit
code word after it has been quantized and the number of bits per sample has
been determined. The encoded words are presented in the last row in the
diagram above. A quantization code of 2 is 010, a quantization code of 5 is 101,
and so on. It's worth noting that the number of quantization levels determines
the number of bits for each sample. The number of bits is nb=log2 L if the
number of quantization levels is L. Because L is 8 in our case, nb equals 3. The
formula may be used to calculate the bit rate.
Bitrate = Sampling rate X Number of bites per sample= ƒs X nb
Delta modulation:
In PCM the signalling rate and transmission channel bandwidth are quite large
since it transmits all the bits which are used to code a sample. To overcome this
problem, Delta modulation is used.
Working Principle:
Delta modulation transmits only one bit per sample. Here, the present sample
value is compared with the previous sample value and this result whether the
amplitude is increased or decreased is transmitted.
Input signal x(t) is approximated to step signal by the delta modulator. This step
size is kept fixed. The difference between the input signal x(t) and staircase
approximated signal is confined to two levels, i.e., +Δ and -Δ.
Now, if the difference is positive, then approximated signal is increased by one
step, i.e., ‘Δ’. If the difference is negative, then approximated signal is reduced
by ‘Δ’ . When the step is reduced, ‘0’ is transmitted and if the step is increased,
‘1’ is transmitted.
Hence, for each sample, only one binary bit is transmitted.

Question – 02:
Write a short note on AC to DC conversion. How to remove noise from the
output?

Solution:
AC-DC converters convert regulated AC power from wall outlets to unregulated
DC power. Transformers alter the voltage of the AC that enters via wall outlets,
rectifiers save it from AC to DC, and a filter eliminates noise from the peaks
and troths of the AC power waves are all included in these power supplies. The
transformer will often scale down the voltage to the voltage required by the item
being fed. The voltage is rectified using a series of diodes in the first stage of
converting AC to DC. Using a rectifier, the sinusoidal AC wave is converted
into a sequence of positive peaks. However, there is still waveform variation -
the period between peaks - to be eliminated at this stage.
A capacitor is employed to filter this out by storing energy
that is subsequently delivered to the load when the voltage decreases. The
capacitor stores incoming energy on the rising edge and expands it when the
voltage drops, minimising voltage droop considerably. In general, the greater
the capacitor's storage capacity, the higher the power supply's quality. The
output fluctuation is smoothed out after voltage conversion by running the
voltage through a regulator to generate a fixed DC output.
Filtering, bypass, and post-regulation are the three most common strategies for
reducing power-supply noise, although there are a few more. One option is to
power your electronics with a battery. When compared to switching or even
linear converters, batteries produce relatively little noise.
Question – 03:
What is Counter ? Provide one example of counting of at least 3 digits through
the counter ?
Solution:
Counter is a digital device, and the output of the counter includes a predefined
state based on the clock pulse applications. The counter's output may be used to
count how many pulses there are. Counters are often made up of a flip-flop
configuration that can be either synchronous or asynchronous. In a synchronous
counter, all flip-flops have the same clock i/p, but in an asynchronous counter,
the flip-o/p flop's is the clock signal from a neighbouring one. The
microcontroller's applications necessitate the counting of external events such as
accurate internal time delay generation and pulse train frequency.
In digital systems and computers, these events are widely utilised. Both events
can be performed using software approaches, however counting loops in
software will not get the precise result since slightly more critical tasks are not
performed. Timers and counters in microcontrollers that are utilised as
interrupts can solve these difficulties.
For example, a 2-bit counter that counts from 002 to 112 in binary, that is 0 to 3
in decimal, has a modulus value of 4 ( 00 → 1 → 10 → 11, and return to 00 ) so
would therefore be called a modulo-4, or mod-4, counter.
Question -04:
What are attenuators? How an attachment works in a multimeter?
Solution:
Every signal, including electrical, communications, entertainment (television),
and other signals, should be transferred from one location to another via a
medium. As the distance travelled by a signal grows, the signal strength
diminishes, making many activities impossible. However, attenuation, or the
progressive reduction of signal intensity over distance, is still beneficial in many
applications. Attenuators are basic passive two-port electrical devices that are
used to decrease the intensity of signals without producing waveform
disruption.
Attenuators work in multimeter as, Attenuator pads or adapters are used to
decrease the amplitude of a signal by a specified amount to permit
measurements or to protect the measuring equipment from signal levels that
might harm it when measuring signals.
Question-05:
Discuss how a Bridge circuit is helpful in showing any sensors output on a
display. What are common ways in this process? Give any one example.
Solution:
Bridge circuits based on resistance are commonly utilised to generate electrical
outputs from sensors that measure physical factors like pressure ,force and light
intensity. Because these outputs are often low, amplification is necessary to
bring them up to the levels required by A/D converters in measurement and
control systems.
Wheatstone bridges in pressure sensors are usually adjusted manually to
eliminate offset and span errors. This necessitates trimming the offset, offset
temperature drift, span, and span temperature drift as part of the instrumentation
manufacturing process. Wheatstone Bridges depicts a bridge that has resistors
added to compensate for these flaws. Getting rid of these mistakes takes time
and money. Alternatively, a programmable dc voltage from a D/A converter can
be applied to the reference pin of an instrumentation amplifier to modify the
offset. Because the offset would otherwise limit the ADC's usable dynamic
range, offset correction is necessary. Gain adjustment is required in most
instrumentation amplifier-based systems due to gain uncertainty in pressure
sensors.
Traditionally, this was accomplished by connecting a trim potentiometer to the
instrumentation amplifier's external gain resistor. System designers used
software-controlled gain adjustment to obtain greater levels of performance
across a broader temperature range. A common example are Manual Bridge
Compensation and Pressure sensing , in above para I mentioned about Manual
Bridge Compensation.