Measurement Systems in Electronics
University of Pitesti
Dolnośląska Wyższa Szkoła Przedsiębiorczości i Techniki w
Polkowicach
Dobrica Adrian
Dr inż. ZDZISŁAW PÓLKOWSKI
Polkowice, 2015
TOPICS MENU
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Definition
Standard Electrical Units
Osciloscope
Operational amplifiers
Voltmeter
Ammeter
Definition
A system of measurement is a set of units of
measurement which can be used to specify anything which can
be measured and were historically important, regulated and
defined because of trade and internal commerce. In modern
systems of measurement, some quantities are designated
as fundamental units, meaning all other needed units can be
derived from them, whereas in the early and most historic eras,
the units were given by fiat (see statutory law) by the ruling
entities and were not necessarily well inter-related or selfconsistent.
http://en.wikipedia.org/wiki/System_of_measurement
Standard Electrical Units
Electrical
Parameter
Measuring
Unit
Symbol
Voltage
Volt
V or E
Current
Ampere
I or i
Resistance
Ohm
R or Ω
Conductance
Siemen
G or ℧
Capacitance
Farad
C
Charge
Coulomb
Q
Inductance
Henry
L or H
Power
Watts
W
Impedance
Ohm
Z
Frequency
Hertz
Hz
http://www.electronics-tutorials.ws/dccircuits/dcp_3.html
Osciloscope
An oscilloscope is a laboratory instrument commonly used to
display and analyze thewaveform of electronic signals. In effect,
the device draws a graph of the instantaneous signal voltage as
a function of time.
http://whatis.techtarget.com/definition/oscilloscope
General Information
• A typical oscilloscope can display alternating current (AC) or pulsating direct
current (DC) waveforms having a frequency as low as approximately 1 hertz
(Hz) or as high as several megahertz (MHz). High-end oscilloscopes can
display signals having frequencies up to several hundred gigahertz (GHz).
The display is broken up into so-called horizontal divisions (hor div) and
vertical divisions (vert div). Time is displayed from left to right on the
horizontal scale. Instantaneous voltage appears on the vertical scale, with
positive values going upward and negative values going downward.
• The oldest form of oscilloscope, still used in some labs today, is known as
the cathode-ray oscilloscope. It produces an image by causing a
focused electron beam to travel, or sweep, in patterns across the face of a
cathode ray tube (CRT). More modern oscilloscopes electronically replicate
the action of the CRT using a liquid crystal display (liquid crystal display)
similar to those found on notebook computers. The most sophisticated
oscilloscopes employ computers to process and display waveforms. These
computers can use any type of display, including CRT, LCD, and gas
plasma.
http://whatis.techtarget.com/definition/oscilloscope
How to use Osciloscope
• In any oscilloscope, the horizontal sweep is measured in seconds per
division (s/div), milliseconds per division (ms/div), microseconds per division
(s/div), or nanoseconds per division (ns/div). The vertical deflection is
measured in volts per division (V/div), millivolts per division (mV/div), or
microvolts per division (?V/div). Virtually all oscilloscopes have adjustable
horizontal sweep and vertical deflection settings.
• The illustration shows two common waveforms as they might appear when
displayed on an oscilloscope screen. The signal on the top is a sine wave;
the signal on the bottom is a ramp wave. It is apparent from this display that
both signals have the same, or nearly the same,frequency.Suppose the
horizontal sweep rate in this instance is 1 µs/div. Then these waves both
complete a full cycle every 2 µs. If the vertical deflection is set for, say, 0.5
mV/div, then these waves both have peak-to-peak amplitudes of
http://whatis.techtarget.com/definition/oscilloscope
approximately 2 mV.
Operational amplifiers
• Operational amplifiers can be used to perform mathematical
operations on voltage signals such as inversion, addition,
subtraction, integration, differentiation, and multiplication by a
constant. You need to understand how to figure out what an
operational amplifier circuit does. We will start with a simple
circuit so that we can examine a method that will permit you to
figure out how these circuits work and then you will have a
more general method you can use for more complex
circuits. So, you have two goals in this section.
http://www.facstaff.bucknell.edu/mastascu/eLessonsHTML/OpAmps/OpAmp2.html
Op-amp basics
• The circuit symbol for an operational amplifier consists simply
of a triangle as shown below. The two inputs are designated by
"+" and "-" symbols, and the output is at the opposite end of the
triangle. Inputs from the "+" input appear at the output in the
same phase, whereas signals present at the "-" input appear at
the output inverted or 180 degrees out of phase. This gives rise
to the names for the inputs. The "+" input is known as the noninverting input, while the "-" input is the inverting input. As the
output from the amplifier is dependent upon the difference in
voltage between the two inputs, it is known as a differential
amplifier.
http://www.radio-electronics.com/info/circuits/opamp_basics/operational-amplifier-basics-tutorial.php
Exampe: Inverting Amplifier
• The circuit we will examine is shown below. This circuit
amplifies a voltage by a factor (- Ro / R1). What is important in
this circuit is that it amplifies by almost exactly (-Ro /R1) so that
the gain of the circuit can be controlled precisely by controlling
the resistor values precisely. The gain of the circuit will not
depend upon paramters of the "Op-Amp". We'll analyze this
circuit to get a mathematical prediction of how it works.
http://www.facstaff.bucknell.edu/mastascu/eLessonsHTML/OpAmps/OpAmp2.html
Voltmeter
• A voltmeter, also known as a voltage meter, is an instrument
used for measuring the potential difference, or voltage, between
two points in an electrical or electronic circuit. Some voltmeters
are intended for use in direct current (DC) circuits; others are
designed for alternating current (AC) circuits. Specialized
voltmeters can measure radio frequency (RF) voltage.
http://whatis.techtarget.com/definition/voltmeter
Analog & Digital Voltmeter
A basic analog voltmeter consists of a
sensitive galvanometer (current meter)
in series with a high resistance. The
internal resistance of a voltmeter must
be high. Otherwise it will draw
significant current, and thereby disturb
the operation of the circuit under test.
The sensitivity of the galvanometer
and the value of the series resistance
determine the range of voltages that
the meter can display.
A digital voltmeter shows voltage
directly as numerals. Some of these
meters can determine voltage values
to several significant figures. Practical
laboratory voltmeters have maximum
ranges of 1000 to 3000 volts (V). Most
commercially manufactured voltmeters
have several scales, increasing in
powers of 10; for example, 0-1 V, 0-10
V, 0-100 V, and 0-1000 V.
http://whatis.techtarget.com/definition/voltmeter
Ammeter
• Ammeters are a type of electronic measuring instrument that
are used to evaluate the flow ofelectric current in a particular
circuit. Essentially, one will measure the flow of current in terms
of amperes. Various designs allow the device to be used in
measuring the amount and rate of current in both small and
large electrical devices.
http://www.wisegeek.org/what-is-an-ammeter.htm
Digital Ammeter
• Digital ammeter designs use a shunt resistor to produce a
calibrated voltage proportional to the current flowing. This
voltage is then measured by a digital voltmeter, through use of
an analog to digital converter (ADC); the digital display is
calibrated to display the current through the shunt. Such
instruments are generally calibrated to indicate the RMS
value for a sine wave only but some designs will indicate true
RMS (sometimes with limitations as to wave shape).
http://en.wikipedia.org/wiki/Ammeter