International Journal of Engineering Trends and Technology (IJETT) – Volume 29 Number 3 - November 2015
Domestic Electrical Supply Monitoring using DSO
Charu Maggu1, Dr.S.K Pahuja2
1
Lecturer, Electrical, SBBSIET, Punjab, India
2
Professor, ICE, NITJ, Punjab, India
Abstract
Present paper proposes a power measurement
method of a single phase electrical load (RLC). Real
time monitoring of power supply is essential for its
continuous and reliable operation. So, this paper also
presents a low cost, low power consuming system
that can be used for fast and precise domestic power
supply parameter monitoring. Simulations analysis of
the voltage waveform, current waveform and the
phase difference between these two signals were done
using DSO. By using this measurement techniques
behavior of any electrical appliances can be checked
and improvement in its working can be possible after
that in it. And also using this measurement technique
we can check which types of harmonics are flowing
in the appliances during its normal working
condition.
1. Introduction to Hardware
The requirement of the load power measurements is
repetitive in the electrical engineering labs and
installations. There are equipment’s available in the
market that can be used to measure these quantities.
Accurate measurement of power and other AC
quantities is very vital at all levels of the electrical
power system.
Fig 1 single line diagram of circuit
The objective of this paper is to design power
measurement system of an electrical load. The load to
be considered in the present study is RLC parallel
ISSN: 2231-5381
circuit. Measurement of single phase instantaneous
voltage and current has been measured with help of
CRO. Voltage is measured with the help of voltage
divider and the instantaneous current is measured
with the help transjector. Then these waveforms are
observed on the screen of CRO. The proposed
method is a low cost power measurement technique.
The load taken into consideration is resistive load,
inductive load and capacitive load. One signal trans
ducted via transjector and the other signal trans
ducted through the voltage divider.
2. Introduction to Digital storage Oscilloscope
Digital Storage Oscilloscope DSO built by Philip
Cupitt . A standard oscilloscope displays variations in
a voltage over time. A simple oscilloscope is of
limited use for non-repeating signals .A storage scope
is more advantageous as it stores the data related to
signal which can be displayed at any time. Because
the screen is not continuously refreshed with the
current state of the signal the scope can be used to
analyze non-repeating signals. Both analogue storage
and digital storage scopes are available, but digital
storage are of greater use.Standard oscilloscopes use
an electron beam, which is swept across a phosphor
screen, the vertical deflection of the beam is directly
proportional to input voltage. Areas of the screen that
are bombarded by the electron beam will emit light
rays, resulting in an image that shows the waveform
of the input signal. Analogue storage scopes use a
specially modified cathode ray tube (CRT) which is
used to store the signal. A Digital Storage
Oscilloscope (DSO) uses digital memory to store a
waveform. In order to do this the incoming signal
firstly digitized once this is complete the data in the
memory can be continuously replayed through a
digital to analogue (D/A) converter and can be
displayed on a CRT.
2.1 Digital Storage Oscilloscope block diagram
An oscilloscope is a device which is used for writing
a time-varying signal to a screen where we
canmeasure maximum and minimum values and we
can observe the behavior of Signals. The DSO writes
on the screen the same way a CRT TV. The DSO
generates a very narrow beam of electrons. On the
inner surface of the screen of DSO there is a
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International Journal of Engineering Trends and Technology (IJETT) – Volume 29 Number 3 - November 2015
phosphorescent material that glows whenever
exposed to radiation and continues to glow for some
while after the radiation is removed.
Fig 2.1 Block diagram of DSO
2.2 Basic front-panel controls
Typically, we can operate an oscilloscope using the
knobs and buttons on the front panel. In extra to
controls found of the front panel, many advance
oscilloscopes now come equipped with operating
systems, and as result, they behave like computers.
You can connectup a mouse and keyboard to the
oscilloscope and use the mouse to adjust the controls
through drop down list and buttons on the display as
well. In addition, some oscilloscopes have touch
screens so you can use a stylus or fingertip to select
the menus. Most oscilloscope front panels contain
four main sections: vertical and horizontal controls,
triggering controls and input controls.
Fig 3.6 Front panel of DSO
2.2.1 Vertical controls
Vertical controls on an oscilloscope are grouped in a
section marked Vertical. These controls permit you to
adjust the vertical aspects of the display. For
example, there will be a control that denotes the
number of volts per division (scale) on the y-axis of
the display grid. You can zoom in on a waveform by
decreasing the division i.e.volts per division or you
can zoom out by increasing this parameter. There
also is a control for the vertical division of the
ISSN: 2231-5381
waveform. This control easily translates the entire
waveform up or down on the display.
2.2.2 Horizontal controls
An oscilloscope's horizontal controls are grouped in a
front panel section marked Horizontal. These controls
are able us to make adjustments to the horizontal
scale of the display. There will be a control that
represent the time per division on the x-axis. Again,
decreasing the time per division enables you to zoom
in on a narrower range of time. There will also be a
control for the horizontal delay. This control makes
youable you to scan through a range of time.
2.2.3 Trigger controls
As we stated earlier, triggering on your signal helps
provide a stable, usable display and permit you to
synchronize the oscilloscope’s acquisition on the part
of the waveform you are interested in viewing.The
trigger controls let you select your vertical trigger
level and select between various triggering
capabilities.
2.2.4 Edge triggering
Edge triggering is the most frequently used
triggering mode. The trigger occurs when the voltage
attain some set threshold value. You can select
between triggering on a rising or a falling edge.
2.2.5 Glitch triggering
Glitch triggering mode make youable to trigger on an
event or pulse whose width is more than or less than
some specified length of time. This capability is very
useful for checking random glitches or errors. If these
glitches do not occur very frequently, it may be very
difficult to analysis them. However, glitch triggering
allows you to check many of these errors.
2.2.6 Pulse-width triggering
Pulse width triggering is quite resembled to glitch
triggering when you are looking for specific pulse
widths. However, it is more often in that you can
trigger on pulses of any specified width and you can
choose the polarity (- or +) of the pulses you want to
trigger. You can also choose the horizontal position
of the trigger. This permits you to see what occurred
pre-trigger or post-trigger. For example, at any
instant you can move a glitch trigger, find the error,
and then see signal pre-trigger to see what caused the
glitch. If you have the horizontal interval set to zero,
your trigger event will be placed in the center of the
screen horizontally. Events that take place right
before the trigger will be on left of the screen and
events that occur directly after the trigger will be on
right of the screen. You also can set the coupling of
the trigger and set the input source you want to
trigger on. You do not always have to trigger on your
signal, but can instead trigger a related signal.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 29 Number 3 - November 2015
2.2.7 Input controls
There are typically two or four analogue channels on
an oscilloscope. They will be numbered and they will
also generally have a button associated with each
particular channel that enables you to turn them on or
off. There may also be a selection that permits you to
specify AC or DC coupling. If DC coupling is
selected, the whole signal will be input. On the other
hand, AC coupling blocks the DC component and
centers the waveform about 0 volts. In addition, you
can mention the probe impedance for each channel
through a selection button. The input controls also
permit s you choose the type of sampling. There are
two ways to sample the signal.
2.2.7.1 Real-time sampling
Real-time sampling samples the waveform often
enough that it take a complete image of the waveform
with each acquisition. Now a day some higher
performance oscilloscopes can capture up to 32-GHz
bandwidth signals in a single-shot utilizing real-time
sampling.
Time Interval=Record Length of sample/Sample
Rate.
3.1 First case: Voltage measurement
Fig 3.1: Instantaneous voltage waveform of main supply
Table 3.1: comparison of voltage readings
Multiplyi
ng factor
Actual
voltage
read
through
DSO(V)
Values
from
voltmeter
(V)
2.26
100
226
228
2
2.20
100
220
224
3
2.28
100
228
228.5
4
2.2
100
220
221.5
5
2.3
100
230
230
Sr.
No
Readi
ng
from
DSO
1
Fig 2.27.1 Trigger control
2.2.7.2 Equivalent-time sampling
Equivalent time sampling builds up the waveform
with many acquisitions. It samples half of the signal
on the first acquisition, then another half on the
second acquisition, and so on. It then collects all this
information together to recreate the waveform.
Equivalent time sampling is usable for highfrequency signals that are too fast for real-time
sampling (>32 GHz).
2.2.8 ADC Resolution
The resolution of the ADC, indicates how precisely it
can convert input voltages into digital values.
Calculation method can improve the effective
resolution.
2.2.9 Record Length
Record length, can be representing as the number of
points that consist of a complete waveform record,
and determines the amount of data that can be
captured with each channel. Since a scope can save
only a limited number of samples, the waveform
duration (time) will be inversely proportional to the
oscilloscope’s sample rate.
ISSN: 2231-5381
3.2 Second case: Current measurement
In this experiment, for the determination of flowing
current in the circuit connect 1ῼ resistance wire in
parallel to the neutral wire. As a result drop takes
place across the wire due to the current flowing in the
circuit. Now this voltage drop gives us the value of
current of the circuit. The purpose of connecting this
1ῼ shunt is to convert the current signal into voltage
Fig 3.2.1: Instantaneous current waveform of load
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International Journal of Engineering Trends and Technology (IJETT) – Volume 29 Number 3 - November 2015
and analytical tools in power quality studies. IEEE T IndAppl 34:
534-548.
[5]. ShindeSachin, PrabhuSapna,(2013)”Labview based digital
CRO for electronic measurement techniques” International Journal
of Engineering Research and Applications (IJERA) ISSN: 22489622, vol. 3, issue 1, pp.693-69
[6]http://uenics.evansville.edu/~amr63/equipment/scope/terminolo
gy.html
Fig 3.2.2: Traced current waveform of load
Table 3.2: comparison of current readings
Sr.
No
.
Load
Current obtained
from DSO(A)
Values obtained
from Current(A)
1
RLC
1.09
1.12
2
RL
1.03
1.18
3
LC
.331
.33
4
RC
.8
.91
5
R
.86
.89
6
L
.54
.55
7
C
.155
.20
4. Conclusion and Future Scope
In this project, disturbances in the two signal i.e.
voltage and current is observed. How power factor is
varied by changing the load can be easily studied.
However, the setup is not tested for capacitive load.
Further same set up can be used in conjunction with
the DSP or Microcontroller and can be used for other
supply parameter estimation specially the supply
frequency, energy consumed and that too using a
single measurement, that may be the part of future
work and scope.
REFERENCES
[1]. Kularatna,Nihal (2007), "Fundamentals of Oscilloscopes",
Digital
and
Analogue
Instrumentation:
Testing
and
Measurement,Institution of Engineering and Technology, pp. 165–
208, ISBN 978-0-85296-999-1
[2]. Sawhney AK, Sawhney P (2003) Electrical and electronics
measurements and measuring instruments. Measurement and
Measurement Systems.
[3]. Artigas JI, Urriza I, Acero J, Barragán LA, Navarro D, et al.
(2009) Power Measurement by Output-Current Integration in
Series Resonant Inverters. IEEE T Ind Electron 56: 559-567.
[4]. Simpson RH (1998) Instrumentation, measurement techniques,
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