portable test measurement
DESCRIPTION
Study about Portable measuring device.TRANSCRIPT
Portable Test Measurement
A Study
Presented to the
College Department
Don Bosco Technology Center
In Partial Fulfillment
of the Requirement for the Degree
Bachelor of Science in Electronics Engineering
By
J. William Achilles D. Young
John Paul G. Suan
Luis Mikael Arzadon
February 2015
Engr. Carlo Pilapil
Adviser
Chapter 1
THE PROBLEM AND ITS SETTING
Introduction
Don Bosco Technology Center is a Catholic institution managed and
operated by Salesian Brothers and Fathers of Don Bosco. Many years had
passed since the first opening of the college program in Don Bosco, the
Bachelor of Science in Technical Education (BSTE). The BSTE program has
three different specialization- Industrial Electronics, Furniture Technology and
Mechanical Technology. Since the opening of the program in 1995, the
institution has produced a number of graduates in the different specializations
(DBTC Student Manual p2). The need for an engineering program that
matches the need of industries prompted DBTC to take the challenge to pilot
their designed engineering program. After some adaptations on the curriculum
and with the capability of the center, the Bachelor of Science in Mechanical
Engineering major in Machine Design and Manufacturing (BSME-MDM) was
offered in year 2002. It is a five- year engineering program leading to
Mechanical Engineering with extra hands-on skills in metal Electronics, and
Computer programming. In 2003, the institution was given a permit to open
two other new engineering programs, the Bachelor of Science in Electronics
and communications Engineering (BSECE), and the Bachelor of Science in
Industrial Engineering major in Furniture Manufacturing (BSIE-FM). BSECE
graduates shall receive a certificate as Junior Engineers and have a primary
career options to work in Telecommunications Industries here and abroad and
do business related opportunities to solid state technology, and semi-
conductor applications. Industrial Engineering focuses on the Furniture Trade
Area. The primary career options of Industrial Engineering are to work in
Furniture Industry positions in facilities planning in the country hence, the
course will serve as its engineering and scientific support (DBTC Student
Manual p3).
1
It is safe to say that one of the primary goals of every college and
university in the Philippines offering the program Electronics Engineering is to
produce well-rounded and competitive professionals in their field of
specialization. The Commission on Higher Education (CHED) is tasked to
supervise and guide private schools, including state universities and colleges
(SUC) to attain this goal by setting standards and mandate minimum
requirements. One of these requirements is to have well-equipped
laboratories, facilities, and equipments where students can developed their
practical skills. The laboratory equipments needed per course must be at least
five (5) sets for newly opened engineering undergraduate programs. The ideal
requirement is to have a ratio of one (1) trainer per trainee or student for the
recognized engineering undergraduate program to ensure comprehensive
learning and training.
Trainees or students having their respective trainers also need test
equipments in order to measure the output or input of the experiments. The
Portable Test Measurement (PTM) is a combination of an oscilloscope,
function generator, and a multimeter. Portable Test Measurement (PTM) can
generate its own frequency input using a function generator and its output
signal can be measured and displayed using an oscilloscope. It can also
measure resistance, voltage and current using a multimeter.
2
Conceptual Background
Figure 1.1: Portable-Test-Measurement(PTM)
The Portable-Test-Measurement (figure 1.1) is an equipment which
has the capabilities of three different types of test equipment, namely, the
oscilloscope, the function generator, and the millimeter.
With the function of the oscilloscope, it is used to display and analyze
the waveform of electronic signals. In effect, the device draws a graph of the
instantaneous signal voltage (figure 1.2) as a function of time.
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Figure 1.2: Instantaneous Signal Voltage
Also, with the ability of the function generator, it would generate a
variety of simple repetitive waveforms. In addition to producing sine waves
(figure 1.3), function generators may typically produce other repetitive
waveforms including square waves (figure 1.4), pulses (figure 1.5), triangular
waveforms (figure 1.6), and sawtooth (figure 1.7). Another feature included on
many function generators is the ability to add a DC offset.
Figure 1.3: Sine wave
Figure 1.4: Square wave
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Figure 1.5: Pulse
Figure 1.6: Triangular wave
Figure 1.7: Sawtooth(ramp) wave
Finally, with the measuring capabilities of the multimeter, it measures
resistance (ohm meter), voltage (voltmeter) and current (ammeter). It can also
be used to measure capacitance, inductance, and temperature. They may
also be able to measure frequency and duty cycle (a measurement relating to
pulse systems such as fiber optic networks).
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Multimeter
Table 1.1
Measurement
Fluke 117 Multimeter
(Industry standard)
PTM-Multimeter
Minimum Maximum Minimum Maximum
Resistance
(Ohms)
0.1Ω 40.0M Ω 0.1Ω 40.0M Ω
Voltage (Volts) 0.1mV 600.0V 0.1mV 600.0V
Current
(Amperes)
0.001A 10.0A 0.001A 10.0A
Continuity 1.000 Ω 600.0 Ω 1.000 Ω 600.0 Ω
Diode test 0.001V 2.000V 0.01V 2.000V
Frequency
(Hertz)
0.1Hz 50.0 kHz 0.1Hz 50.0kHz
Capacitance
(Farad)
1nF >1000uF N/A N/A
Fluke 117 (Industry standard) vs. PTM-Multimeter comparison
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Oscilloscope
Table 1.2
Tektronix TDS3000C
Digital Oscilloscope
PTM-Oscilloscope
Bandwidth 300 MHz 100 Mhz
Rise time (typical) 1.2 nS 1.0 nS
Sample rate
(per channel)
2.5 GS/s 1.5 GS/s
Input coupling AC, DC, GND AC, DC, GND
Input impedance 1MΩ, parallel with 13pF
or 50Ω
1MΩ, parallel with 13pF
or 50Ω
Input sensitivity range 1MΩ 1mV/div – 10V/div
50Ω 1mV/div - 1V/div
1MΩ 1mV/div – 10V/div
50Ω 1mV/div - 1V/div
Position range ±5 div ±5div
Power source
(AC)
100VRMS to 240VRMS
±10%
220VRMS ±10%
Tektronix TDS3000C Digital Oscilloscope vs. PTM-Oscilloscope
comparison
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Function Generator
Table 1.3
Agilent-HP 8662A
Function Generator
PTM-Function
Generator
Frequency Range 10 kHz to 1280 Mhz 10 Hz to 1Mhz
Resolution 0.1 Hz 0.5 Hz
Level Range +13 to -139.9 dBm +10 to -50 dBm
Agilent-HP 8662A Function Generator vs. PTM-Function Generator
comparison
8
Theoretical Background
Multimeter
A multimeter or a multitester, also known as a VOM (Volt-Ohm meter),
is an electronic measuring instrument that combines several measurement
functions in one unit, namely; the Voltmeter, the Ammeter, and the
Ohmmeter. A typical multimeter would include basic features such as the
ability to measure voltage, current, and resistance. A multimeter can be a
hand-held device useful for basic fault finding and field service work, or
a bench instrument which can measure to a very high degree of accuracy.
They can be used to troubleshoot electrical problems in a wide array of
industrial and household devices such as electronic equipment, motor
controls, domestic appliances, power supplies, and wiring systems.
Voltmeter
A voltmeter measures the change in voltage between two points
in an electric circuit and therefore must be connected in parallel with
the portion of the circuit on which the measurement is made (figure
1.8). In analogy with a water circuit, a voltmeter is like a meter
designed to measure pressure difference. It is necessary for the
voltmeter to have a very high resistance so that it does not have an
appreciable effect on the current or voltage associated with the
measured circuit. Modern solid-state meters have digital readouts, but
the principles of operation can be better appreciated by examining the
older moving coil meters based on galvanometer sensors.
9
Figure 1.8: Voltmeter Circuit Diagram
Ammeter
An ammeter is an instrument for measuring the electric
current in amperes in a branch of an electric circuit. It must be placed
in series with the measured branch, and must have very low resistance
to avoid significant alteration of the current it is to measure (figure 1.9).
The analogy with an in-line flow meter in a water circuit can help
visualize why an ammeter must have a low resistance, and why
connecting an ammeter in parallel can damage the meter. Modern
solid-state meters have digital readouts, but the principles of operation
can be better appreciated by examining the older meters based
on galvanometer sensors.
Figure 1.9: Ammeter Circuit Diagram
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Ohmmeter
The standard way to measure resistance in ohms is to supply a
constant voltage to the resistance and measure the current through it (figure
1.10). That current is of course inversely proportional to the resistance
according to Ohm's law, so that you have a non-linear scale. The current
registered by the current sensing element is proportional to 1/R, so that a
large current implies a small resistance. Modern solid-state meters have
digital readouts, but the principles of operation can be better appreciated by
examining the older moving coil meters based on galvanometer sensors.
Figure 1.10: Ohmmeter Circuit Diagram
Voltmeter / Ammeter Measurements
The value of electrical resistance associated with a circuit element or
appliance can be determined by measuring the voltage across it with
a voltmeter and the current through it with an ammeter and then dividing the
measured voltage by the current (figure 1.11). This is an application of Ohm's
law, but this method works even for non-ohmic resistances where the
resistance might depend upon the current. At least in those cases it gives you
the effective resistance in ohms under that specific combination of voltage
and current.
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Figure 1.11: How to measure voltage and current
Voltage and Frequency Measurements
To measure voltage or frequency of a particular electrical signal, the
oscilloscope is setup to display a graph of voltage versus time. The signal to
be measured is applied to either the CH1 or the CH2 inputs. Triggering is set
to show a trace on the screen. Then the vertical (VOLTS/DIV) and horizontal
(SEC/DIV) scaling controls are adjusted to show the signal to be measured
appropriately on the screen. With all the knobs in their calibrated position, the
instantaneous voltage at any time can be read directly from the y-axis and the
period T (time for one cycle) can be read from the x-axis. Including
uncertainty) with the oscilloscope are made by reading the number of
divisions on the screen and multiplying by the scaling factor. The scaling
controls for uncertainty considerations are taken to be exact (as with most
measuring instruments, their calibrations are much more exact than the
reading of that instrument).
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Peak to peak voltage (actually measured trough to peak) is one type of
voltage measurement
Peak to Peak Amplitude = (5.2±0.1Div)(2V/Div) (Eq. 1.1)
= (5.2Div±2.0%)(2V/Div)
= (5.2Div)(2V/Div)±2.0%
= 10.40±0.20V
The period in this example was determined over two cycles for
increased accuracy. The greatest accuracy is attained by measuring
over the greatest part of the screen (same as in graphing where slope
is determined from points with the most separation).
Period = (8.0±0.1Div)(1ms/Div)/(2cycles) (Eq. 1.2)
= (8.0Div±1.3%)(1ms/Div)/(2cycles)
= (4.0ms)±1.3%
= 4.000±0.052ms
From the period, frequency is calculated;
Frequency = 1/Period (Eq. 1.3)
=1/(4.000±0.052ms)
=1/(4.000ms±1.3%)
=.25ms−1±1.3%
=0.2500±0.0033ms−1
=250.0±3.3Hz
(1Hz = 1 Cycle/sec)
Waveforms
A function generator is a very versatile instrument that is extensively
used in electronics, mechanics, bioengineering, physics and many other
fields. It allows you to create a wide variety of synthesized electrical signals
and waveforms for testing and diagnostic applications. Figure 1.12 shows the
most common functions such as the sine, square, triangle and ramp functions.
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Figure 1.12: Sample Waveforms
Each of the waveforms can be adjusted through the front panel
controls or remotely for frequency, amplitude and DC offset voltage. As an
example, let’s look at a sine function described by the following equation,
v(t)=VAsin(21ft) + VOFF (Eq. 1.4)
In which f is the frequency, VA the amplitude, and VOFF the offset voltage
as shown in Figure 1.13. Instead of amplitude one often used the RMS (Root
Mean Square) value to express the signal voltage level. For a sine wave the
RMS value is the amplitude divided by the square root of 2 or VRMS = VA/1.41.
The RMS is the most useful way to specify AC signal amplitudes.
4
Figure 1.13: Sine wave with amplitude VA , frequency f, and offset VOFF
Functions and Use of a Waveform Generator
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The function generator is based on digital signal processing (DSP)
methods. A DSP is basically a beefed-up microprocessor which is specially
designed for number crunching. DSPs are used in many everyday
instruments ranging from a compact disc player, an electronic synthesized
piano, or a voice-synthesized telephone answering message system. The
DSP is able to generate complex and arbitrary functions. The principle if fairly
simple and is called Direct Digital Synthesis. A simplified block diagram is
shown in Figure 1.14.
Figure 1.14: Block diagram of the waveform generator.
The heart of the instrument is a random-access-memory (RAM) which
stores the function (e.g. sine) in digital form. This memory is addressed
sequentially through an increment register. The frequency of the voltage
waveform is proportional to the speed with which the RAM is addressed. The
output data from the memory is a digital bit stream which is converted in the
actual (analog) wave shape through a Digital-to-Analog Converter (DAC). A
low pass filter at the output ensures a smooth waveform. The amplitude and
offset are controlled by changing the signal gain of the amplifier at the output
of the DAC.
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Any circuit can be represented by the Thevenin's equivalent circuit.
This is shown in Figure 1.15a. Vgen represents the waveform (sine, pulse, etc.)
and RT is the Thevenin resistance (output resistance).
Figure 1.15: (a) Thevenin's equivalent circuit; (b) Voltage divider
between the output and load resistors.
Important is that this output resistance of the function generator has a
value of 50 Ohm. This implies that the actual output voltage one measures
over the load will vary with the load resistance because of the voltage divider,
as shown in Figure 1.15b. The output amplitude is calibrated for a 50 Ohm
load resistance, which means that the voltage shown on the function
generator's display panel corresponds to the actual voltage VLOAD over the
load only when the load is equal to 50 Ohm. In other words, the value of
Vgen is double of the value displayed (or selected) by the function generator. If
the function generator's output is measured with no load connected (open
circuit or infinite resistance), the output voltage will be twice the displayed
amplitude. Thus, be careful when applying the output voltage of the function
generator to a circuit whose input resistance is different from 50 Ohm. In
general, it is a good practice to measure the amplitude of the waveform using
a Digital Multimeter (DMM) or an oscilloscope instead of relying on the
function generator display reading.
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Statement of the Problem
The main purpose of this project is to make sure that every trainer has
its own corresponding test equipment, to make things more convenient for the
students or trainees, and to make it easier to store and organize.
Specifically, the study aims to answer the following questions:
1. Designing, conceptualizing, and fabricating three (3) test
equipments, making it as a single equipment.
2. The effectiveness of the Portable Test Measurement is in contrast to
its individual equipments.
3. Some components for the Portable Test Measurement would be
from abroad.
4. The Portable Test Measurement is easy to repair.
Significance of the Study
The study is important because it is a need, a requirement and a
technology to look into. This will solve the worries of local schools in providing
quality hands-on education without fear of high cost test equipments. This
study is beneficial to the following:
School Administration – They will not have a hard time in keep track
of the equipments since the number of equipments are lessened and their
functionality the same.
Engineering Schools – The schools offering Bachelor of Science in
Electronics Engineering.
College Students – They are the beneficiaries of the equipments, and
their hands-on experience and knowledge will be enhanced.
Industries – They are the provider of jobs for Engineering Graduates.
With the result of this study they are assured that graduates from this
institution are well-rounded and prepared for the industry’s needs.
Future Researchers – They could probably add more features to the
PTM and use this study as basis.
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Scope and Limitations
Scope
This project includes imitation and fabrication of oscilloscope,
multimeter, and function generator using different components but of the
same function as the original ones.
Limitation
The specifications of the Portable Test Measurement are for laboratory
use only.
Multimeter
Voltmeter
o Maximum voltage measured = ±500 Vpeak
o Minimum voltage measured = 0v AC/DC
Ammeter
o Maximum current measured = 2000mA
o Minimum current measured = 0A
Ohmmeter
o Maximum resistance measured = 200 MΩ(ohms)
o Minimum resistance measured = 200 Ω(ohms)
Function Generator
Oscilloscope
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Definition of Terms
1. Alternating Current (AC) - an electric current that reverses its direction
many times a second at regular intervals, typically used in power supplies.
2. Direct Current (DC) - an electric current flowing in one direction only.
3. Frequency - is the number of occurrences of a repeating event per unit
time.
4. Resistance - is an electrical quantity that measures how the device or
material reduces the electric current flow through it. The resistance is
measured in units of ohms
5. Current - is a flow of electric charge. In electric circuits this charge is often
carried by moving electrons in a wire. It can also be carried by ions in an
electrolyte, or by both ions and electrons such as in plasma.
6. Voltage - is electric potential difference between two points of an electric
field.
7. Amperes - often shortened to amp, is the SI unit of electric current.
8. Period - the time between cycles of a periodic wave.
9. Amplitude - the maximum extent of a vibration or oscillation, measured
from the position of equilibrium.
10.Peak-to-peak amplitude - is the change between peak (highest amplitude
value) and trough (lowest amplitude value, which can be negative). With
appropriate circuitry, peak-to-peak amplitudes of electric oscillations can
be measured by meters or by viewing the waveform on an oscilloscope.
Peak-to-peak is a straightforward measurement on an oscilloscope, the
peaks of the waveform being easily identified and measured against the
graticule. This remains a common way of specifying amplitude, but
sometimes other measures of amplitude are more appropriate
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