Transcript AVOP-ELEKTRO-HOL-001

Learning program: Mechanic – electrician
Name of the program: II. class
Numerical systems
Analog and numerical representation of quantities
Made by: Mgr. Holman Pavel
Projekt Anglicky v odborných předmětech, CZ.1.07/1.3.09/04.0002
je spolufinancován Evropským sociálním fondem a státním rozpočtem České republiky.
Numerical systems
To start with, I’d like to compare analog and numerical method.
If we should choose from analog (analogue) measuring device or
digital measuring device, which one shall we choose?
We choose the digital one
because of its undisputable advantages. If we measure for example
the electric current, the pointer of the analog ammeter is
proportionate to the measured voltage.
If we want to measure the result, we have to compare the position of
the pointer with the scale.
The scale is divided into segments, which correspond
to the certain part of the device degree.
One segment corresponds to the certain value
(f.e. 1 segment = 100 mA).
That’s why we have to guess the real value of the measured quantity.
If someone else measures the same figure, he may guess a different value
on the scale.
But if we measure the electrical current by a numerical ammeter, the
current value figure is determined by the group of numbers on the
digital device display.
The projection is then clear and everybody will have the same
results. Another advantage of numerical devices could be an
automatic setting of the best working scope and the correct
projection of the measured quantity sign.
We can conclude that the numerical projection of the measured quantity is more
accurate.
Compared to that, the analog figure is perceived and assessed often faster. For
example a time figure on the analog wrist watch can be often evaluated easier
than the figure on the watch with the numerical display.
Analog quantities are continuous functions of time (f.e. voltage).
It means that each analog quantity can have in any interval indefinite number of
values. The signal is due to the material imperfection and the external
environment distorted or degraded during its processing. Most important thing
is that the value isn’t changing rapidly and has a definitive value in each
moment.
Analog quantities are measured and processed via analog circuits. Analog
quantities (voltage, electrical current) can be measured by numerical devices.
An analog signal has to be transferred to the numerical signal, which is then
further processed.
Measured physical quantities, which can be found all around us, are
almost always analog (temperature, pressure, voltage, current).
Circuits processing signals can be divided into two basic groups:
1. Analog circuits
2. Numerical circuits
Analog circuits - process signals, which are functions of time and are
continuous in time, meaning that they are changing continuously.
They are for example sound waves, light radiation, the temperature of
the environment or previously mentioned voltage signal as a function
of time, which is also analog.
Continuous analog signal
2. Numerical circuits- process most often double-value signals. These
signals are called binary or logical.
A binary signal is determined by the combination of a number of bits
so high to represent an analog signal with the adequate accuracy by a
numerical signal.
The picture depicts the example of the binary signal by using four
bits. We can see, that there is a definite number of levels represented
by a group of nulls and ones for voltage values depiction.
Example of the numerical level signal
According to the quantity measured
by measuring devices, we distinguish:
According to the measuring method
we distinguish devices to measure:
Voltmeters – measure voltage,
Ammeters – measure electrical
current,
Ohmmeters – measure electrical
resistance,
Wattmeters – measure electrical
power,
Electricity meters – measure electrical
work (energy) of the electric current,
Oscilometers– measure frequency of
the electric current,
Phasemeters – measure (cos Φ),
Galvanometers – measure very low
electric currents, voltage and charges.
One electrical quantity in stable
stage (f.e. current, voltage, …),
galvanometr
An addition and a subtraction of
electrical quantities (f.e. tree-phase
electric meter, variance voltmeter,
…)
Electric quantities product (f.e.
wattmeter),
Electric quantities quotient ( f.e.
ohmmeter),
Electric quantities time integral (f.e.
electric meter).
According to the device use we
distinguish:
Distributor devices – permanently
attached in distributors, switching
stations or in control rooms. They
serve as constant measuring
devices.
Portable devices (assembly) – used
for the workshop measuring, often
constructed as universal (measure
more quantities).
Laboratory devices – used for the
accurate measuring in laboratories
and testing rooms.
Standards – are the most accurate
devices used for laboratory results
verification.
According to the measuring device
apparatus we distinguish:
Magnetic-electric
Ferromagnetic
Electrodynamic and ferrodynamic
Inductive
Electrostatic
Thermic
Vibrational
According to the pointer type we
distinguish:
Analog – divergence is showed by the
pointer – most common
With the light trace – there is a light ray on
the scale, which is rebound from the mirror
located on the revolving device
Recording (registration) – the divergence is
graphically recorded by the liner on the
paper strip
Vibratory – the divergence is realized by the
oscillation of steel needles
Question for 1 000 Kč
Which device measures voltage?
a) Ammeter
c) Voltmeter
b) Ohmmeter
d) Phasemeter
Question for 2 000 Kč
What is the basic unit of electric
current?
a) Ampere
c) Volt
b) Ohm
d) Watt
Question for 3 000 Kč
While processing which signal outer
environment conditions cause distortion
or other signal degradation?
a) Numerical
c) Digital
b) Binary
d) Analog
Question for 5000 Kč
Numerical circuits most often process
signals:
a) Decimal
c) Binary
b) Analog
d) Sexagesimal
Question for 10 000 Kč
Convert: 100 mA = ??? A
a) 1,0 A
c) 10 A
b) 0,1 A
d) 0,01 A
Question for 20 000 Kč
Which measuring devices are
being used for constant
measuring?
a) Standards
c) Laboratory
b) Distributor
d) Portable
Question for 50 000 Kč
Quotient of electric quantities is
measured by:
a) Voltmeter
c) Wattmeter
b) Ohmmeter
d) Ammeter
Question for 100 000 Kč
Measured electrical quantities
occurring in our surroundings
are:
a) Analog
c) Digital
b) Numerical
d) Logic
Question for 200 000 Kč
Which measuring devices are the most
accurate?
a) Standards
c) Laboratory
b) Distributor
d) Portable
Question for 500 000 Kč
Which measuring devices measure very
low current, voltage and charges?
a) Wattmeters
c) Galvanometers
b) Phasemeters
d) Oscilometers
Question for 1 000 000 Kč
Which analog measuring devices have
the divergence recorded by the liner on
the paper strip?
a) Analog
b) With the light trace
c) Recording
d) Vibratory
Sorry your answer is wrong.
End of the game
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Mužík, J. Management ve vzdělávání dospělých. Praha: EUROLEX BOHEMIA, 2000. ISBN
80-7361-269-7.
Operační program Vzdělávání pro konkurenceschopnost, ESF 2007 – 2013.
Dostupné na: http://www.msmt.cz/eu/provadeci-dokument-k-op-vzdelavani-prokonkurenceschopnost
ANTOŠOVÁ,M., DAVÍDEK. V. Císlicová technika.Ceské Budejovice: KOPP, 2004.
ISBN 80-7232-206-0.
JANSEN, H., ROTTER, A. A KOL. Informacní a telekomunikacní technika. Praha:
EUROPA- SOBOTÁLES cz.,2004. ISBN 80-86706-08-7.
Pecina, J. Ing. PaedDr. CSc.; Pecina, P. Mgr. Ph.d. Základy císlicové techniky. Brno: