TOPIK 2: TEST EQUIPMENT
MULTIMETER
1. A Multimeter or Multi tester, is an electronic measuring instrument used to measure
Voltage, Current , Resistance and continuity.
2. The name “Multi” meter, refer to the combination of the functionalities of Voltmeter,
Ammeter and Ohmmeter.
3. With Multimeter, we can check
• Check if the switch (or push button) is properly working or not.
• Measure the amount of current flowing through a device, like an LED.
• Measure the voltage of a battery.
• Check if the wire is conducting electricity or not.
4. Multimers can test three major things
a. Continuity. This tests if electricity can flow through the component.
b. Resistance.
c. Voltage
5. The important factor that must be considered while using a multimeter is setting the
range of voltage and current to a maximum value. If there is an OL displayed in a digital
multimeter while checking then we must know that the source that we measured is
beyond our set value and an ‘OL’ refers to overload.
6. Parts of a Multimeter
• Display
• Selection Knob
• Ports
• Probes
7. The measured value is displayed on the LCD Display of the Multimeter.
8. Multimeter Probes
• connect the Black probe to the COM port.
• red probe is usually connected to the port with label VΩmA. In this configuration,
you can measure AC and DC voltage, DC current in mA and Resistance,
• Use the other port with label 10ADC to measure DC Current up to 10A. The 10A
port will usually be marked whether there is an internal fuse or not. Be very
careful when using this port and do not use this port for long continuous durations
(not more than 10s).
• 10A is used when measuring large currents, greater than 200mA
• µAmA is used to measure current
• VΩ allows you to measure voltage and resistance and test continuity
9. How to use a Multimeter?
Measuring Voltage
Using a Digital Multimeter, you can measure both the DC and AC Voltage.
The Voltmeter section of the Multimeter is usually marked as “V” and depending on
AC or DC measurement, there will be additional indications.
➢ DC Voltage
If there is a straight line adjacent to the “V”, then it is used to measure DC Voltage.
Plug-in the correct probes into the Multimeter (if they are not already plugged in) and
set the knob to measure DC Voltage.
DC Voltage Measurement Knob Selection
•
But there are a bunch of positions in DC Voltage measurement. Which one do
you select? The number to which knob points to is the maximum value that we
can measure of that particular parameter, DC Voltage in this case.
•
So, if you set the knob to 20, then you can measure DC Voltages up to 20V.
As you can see from the image, there are 5 positions associated with DC
Voltage measurement (200m, 2000m, 2, 20, 200, 600). This particular
Multimeter can measure a maximum DC Voltage of 600V.
•
In case you want to measure the voltage of a 9V battery, then set the knob to
20. What happens if you set the range lower than the measuring value? In this
case, the LCD will display 1, indicating that the result has exceeded the range.
Steps to measure voltage:
a) Set the mode to V with a wavy line if you’re measuring AC voltage or to the V with a
straight line if you’re measuring DC voltage.
b) Make sure the red probe is connected to the port with a V next to it.
c) Connect the red probe to the positive side of the component, which is where the current
is coming from.
d) Connect the COM probe to the other side of the component.
e) Read the value on the display.
Tip: to measure voltage you have to connect your multimeter in parallel with the component
you want to measure the voltage. Placing the multimeter in parallel is placing each probe along
the leads of the component you want to measure the voltage.
1. Measure voltage 1.5V battery
a. Select a range with the selection knob that can read the 1.5V. (in this case select range
2V). but If we use digital multimeter, we don’t have to select the range.
b. What if you didn’t know what was the value of the voltage? If you need to measure
the voltage of something, and you don’t know the range in which the value will fall,
you need to try several ranges.
c. If the range you’ve selected is lower than the real value, on the display you’ll read 1
as shown in the picture below. The 1 means that the voltage is higher than the range
you’ve selected.
d. If you select a higher range, most part of the times you’ll be able to read the value of
the voltage, but with less accuracy.
If the red and black probe is switch, the reading on the multimeter has the same value,
but it’s negative.
Example: measuring voltage in a circuit
In this example we’ll show you how to measure the voltage drop across a resistor in a simple
circuit. This example circuit lights up an LED.
TIP: two components in parallel share voltage, so you should connect the multimeter probes
in parallel with the component you want to measure the voltage.
To wire the circuit you need to connect an LED to 9V battery through a 470 Ohm resistor.
To measure the voltage drop across the resistor:
1. You just have to place the red probe in one lead of the resistor and the black
probe on the other lead of the resistor.
2. The red probe should be connected to the part that the current is coming
from.
3. Also, don’t forget to make sure the probes are plugged in the right ports.
➢ AC Voltage
WARNING: Measure AC Voltage with extreme caution and preferably under a professional
supervision. Make sure that the probes are properly inserted in to the Multimeter ports without
any exposed metal. Do not touch the probes by the tips. AC Mains can be very dangerous. If
in doubt, better not to use Multimeter for AC Mains Voltage measurement.
A sine wave symbol adjacent to the “V” indicates AC Voltage measurement. As you can see
from the image, this particular Multimeter can measure AC Voltage up to 600V and has only
two range selection positions (200 and 600).
Let us measure the Mains AC voltage for the purpose of demonstration. Personally, I do not
recommend beginners to go anywhere near Main AC.
To measure AC mains Voltage, set the knob to 600 in AC Voltage Measurement (V with a
Sine Wave). I chose 600 because my mains supply is 240V. Always set the knob for AC
Voltage measurement before inserting the probes.
Now, Insert the probes into the socket and you can see the measured AC Voltage displayed
on the LCD.
Measuring Current
1. current in components connected in series is same.
2. Using this basic principle, we have to make the Multimeter a part of the circuit so that
same current passes through the Multimeter as in the component.
3. The Ammeter section of the Multimeter is indicated by the symbol A. Another
important point to note is that most Digital Multimeters can only measure DC Current.
So, there will be a straight line adjacent to the A to indicate DC Current
measurement.
➢ DC Current
1. To measure DC Current, set knob of the Multimeter to DC Current measurement.
This particular Multimeter can measure DC Current from few µA to 200mA. This
range is sufficient for measuring current in LEDs.
2. set the range to 200mA and connected the Multimeter as per the following circuit.
Consider the Multimeter in Ammeter mode as essentially a wire through which the
current flows to the main circuit.
3. In this configuration, Multimeter becomes a part of the circuit and if you disconnect
any probe, then the circuit will not work. The measured current is displayed on the
LCD.
To measure the current, you need to connect your multimeter in series with your circuit.
TIP: to place the multimeter in series, you need to place the red probe on the lead of a
component and the black probe on the next component lead. The multimeter acts as if it was
a wire in the circuit. If we disconnect the multimeter, your circuit won’t work.
Testing Continuity
1. The continuity test is essentially a low resistance measurement. If the resistance
between two points is very less (usually few Ohms), then those two points are
considered as electrically connected and the buzzer starts the sound.
2. It is used to test continuity from point A to B in a circuit, whether a wire is conducting
or not, whether a switch is properly functioning or not.
3. The continuity test function is usually represented by a “speaker” symbol.
4. Set the knob to test for continuity and connect the probes across a wire. If the wire is
in good condition without any breakage, then you will hear a continuous buzzer. If
there is a problem in the wire, you won’t hear any sound.
5. It also helps you check if two points of the circuit are connected.
How does continuity work?
6. If there is very low resistance between two points, which is less than a few ohms, the
two points are electrically connected and you’ll hear a continuous sound.
7. If the sound isn’t continuous or if you don’t hear any sound at all, it means that what
you’re testing has a faulty connection or isn’t connected at all.
8. WARNING: To test continuity you should turn off the system! Turn off the power
supply!
9. Touch the two probes together and, as they are connected, you’ll hear a continuous
sound.
10. To test the continuity of a wire, you just need to connect each probe to the wire tips.
MULTIMETER
EXAMPLE OF CONTINUITY TESTING
B
VOLTAGE TESTING
BACAAN BUMI NEUTRAL SHOULD BE NO READING. IF THE READING IS 180.. THERE
MIGHT NOT WIRING CORRECTLY
OSCILLOSCOPE
1.
Oscilloscope is test equipment used for testing and fault-finding a variety of electronic
circuits from logic circuits through analogue circuits to radio circuits and displays waveforms
with the following information:
a)
b)
c)
d)
e)
The amplitude of the signal
The shape of the signal
The behaviour of the signal
Frequency of the signal
and much more.
2. Function of an oscilloscope
•
The function of an oscilloscope is to be able to display waveforms on some form of
display. In the normal mode of operation time is displayed along the X-axis (horizontal
axis) and amplitude is displayed along the Y axis (vertical axis).
•
By seeing a waveform in this manner, it is possible to see analyse the operation of the
circuit and discover why any problems may exist.
3. Types of oscilloscope:
a. There are several different types of oscilloscope from analogue to digital and
more. The first types of oscilloscope were analogue, but with the advances in
digital technology, virtually all new test instruments these days are processor
controlled and use digital signal processing to provide excellent displays of the
waveforms.
b.
4. Scope specifications: accuracy, time base range, upper frequencies and the like are
essentially the same, digital scopes also have specifications to items like the number of
DAC bits, memory depth and the like that are specific to digital oscilloscopes.
5. How to use an oscilloscope:
a. Although oscilloscopes are easy to use these days, it helps to understand how these
items of electronics test equipment work and what controls there are and how they
operate. There are even soft keys on the screen, so there is a lot that can be done.
6. Oscilloscope triggering:
a. The trigger function is one of the most important functions on an oscilloscope. The
scope trigger enables the time-based to "start" at the same point on each cycle of the
waveform and this enables to be displayed so it appears still on the screen.
The oscilloscope trigger function has developed considerably since most scopes moved to
use digital technology. The digital signal processing available enables the trigger to provide
more flexibility and greater functionality so that signals can be investigated more closely to
discover problems and issues.
b. Oscilloscope probes: Any oscilloscope will need probes to attach to the unit under test.
The performance and use of these scope probes enables the best to be made of the actual
test instrument, so knowing which probes to select, how to set them up, and the limitations
are essential for a true understanding of the measurements made.
A typical oscilloscope
Oscilloscope exterior
An oscilloscope will normally have a large array of items on the exterior of the case.
A high performance oscilloscope
The front panel of the test equipment will typically have a number of items on it:
1. Display: used to display the waveform.
2. Connectors:
a) There is a variety of different connectors on the front panel. Typically there is an
input for each of the channels to be displayed - often an oscilloscope will have more
than one channel.
b) Many oscilloscopes are dual channel and can therefore display two signals at the
same time, allowing waveforms to be compared. Other inputs may include a trigger
input that will enable the trace on the oscilloscope to be triggered according to this
signal.
3. Controls :
1. Vertical gain/signal input sensitivity: This is generally calibrated in V/cm, i.e. each
vertical division on the scale represents a given number of volts.
2. Time base: This alters the speed at which the trace crosses the screen horizontally on
the oscilloscope. It is calibrated in terms of time/division, e.g. 1ms / cm, assuming the
divisions are at one-centimetre intervals.
3. Trigger: The controls that are associated with the trigger enable the timebase of the
oscilloscope to be triggered in various ways. This enables a still or stable picture to be
obtained on the screen of the oscilloscope.
How to use an oscilloscope
The basics or instructions of how to use an oscilloscope, and using an oscilloscope to
measure and fault find electronics circuits.
Basic oscilloscope controls
•
In view of the flexibility and level of control required to use an oscilloscope, there are
a large number of controls that are present. These need to be set correctly if the
required view of the signal is to be obtained.
1. Vertical gain:
This control on the oscilloscope alters the gain of the amplifier that
controls the size of the signal in the vertical axis. It is generally calibrated in terms of a
certain number of volts per centimetre. Therefore by setting the vertical gain switch so
that a lower number of volts per centimetre is selected, then the vertical gain is
increased and the amplitude of the visible waveform on the screen is increased.
When using the oscilloscope, the vertical gain is normally set so that the waveform fills
the vertical plane as best as possible, i.e. as large as possible without going outside
the visible or calibrated area.
2. Vertical position: This control on the oscilloscope governs the position of trace when
no signal is present. It is normally set to a convenient line on the graticule so that
measurements above and below the "zero" position can be measured easily. It also
has an equivalent horizontal position control that sets the horizontal position. Again
this one should be set to a convenient position for making any timing measurements.
3. Timebase: The timebase control sets the speed at which the screen is scanned. It is
calibrated in terms of a certain a certain time for each centimetre calibration on the
screen. From this the period of a waveform can be calculated. This if a full cycle of a
waveform too 10 microseconds to complete, this means that its period is 10
microseconds, and the frequency is the reciprocal of the time period, i.e. 1 / 10
microseconds
=
100
kHz.
Normally the timebase is adjusted so that the waveform or a particular point on the
waveform under investigation can be seen at its best.
4. Trigger: The trigger control on the oscilloscope sets the point at which the scan on
the waveform starts. On analogue oscilloscopes, only when a certain voltage level had
been reached by the waveform would the scan start. This would enable the scan on
the waveform to start at the same time on each cycle, enabling a steady waveform to
be displayed. By altering the trigger voltage, the scan can be made to start at a different
point on the waveform. It is also possible to choose whether to trigger the oscilloscope
on a positive, or a negative going part of the waveform. This may be provided by a
separate switch marked with + and - signs.
5. Trigger hold-off:
This is another important control associated with the trigger
function. Known as the "hold-off" function it adds a delay to the trigger to prevent it
triggering too soon after the completion of the previous scan. This function is
sometimes required because there are several points on a waveform on which the
oscilloscope can trigger. By adjusting the hold-off function a stable display can be
achieved.
6. Beam finder:
Some oscilloscopes possess a beam finder function. This can be
particularly useful as it is possible that sometimes the trace may not be visible.
Pressing the beam finder button enables the beam to be found and adjusted so that it
is in the centre of the screen.
First steps in using an oscilloscope
1. Turn power on and Wait for oscilloscope display to appear
2. Find the trace: set the trigger to the centre and the hold-off turned fully counter-clockwise.
Also set the horizontal and vertical position controls to the centre, if they are not already
there. Press the "beamfinder" if the trace is invisible.
3. Set the gain control: If the waveform is expected to be 8 volts peak to peak, and the
calibrated section of the screen is 10 centimetres high, then set the gain so that it is 1 volt
/ centimetre. This way the waveform will occupy 8 centimetres, almost filling the screen.
4. Set the timebase speed.
5. Apply the signal: With the controls set approximately correctly the signal can be applied
and an image should be seen.
6. Adjust the trigger: At this stage it is necessary to adjust the trigger level and whether it
triggers on the positive or negative going edge. The trigger level control will be able to
control where on the waveform the timebase is triggered and hence the trace starts on the
waveform. The choice of whether it triggers on the positive or negative going edge may
also be important. These should be adjusted to give the required image.
7. Adjust the controls for the best image: With a stable waveform in place, the vertical
gain and timebase controls can be re-adjusted to give the required image.
Oscilloscope Trigger: Triggering a Scope
• The oscilloscope trigger function enables repetitive waveforms to be displayed on the
screen in steady fashion. The trigger enables the timebase to start its scan at the same
point on each repetition of the waveform.
• In this way the oscilloscope trigger enables the waveforms to be viewed in a
meaningful manner, otherwise the timebase would start at a random point on the
waveform each time the waveform is repeated and the image of the waveform would
not be meaningful.
Oscilloscope trigger concept
•
•
The basic concept behind the oscilloscope trigger function is that some of the incoming
waveform is fed into comparator circuit.
Oscilloscope front panel showing trigger controls
•
•
When the voltage of the waveform reaches a required level, then a comparator
switches and send a start signal to the timebase. This enables the timebase to exactly
synchronise with the displayed waveform so that it remains stable on the screen.
Oscilloscope trigger level and slope
•
•
In order to be able to capture the required view on the scope, the trigger can be
adjusted in two main ways: both the level and the direction of the slope can be selected
on both analogue and digital oscilloscopes.
The trigger voltage level control sets the voltage at which the trigger fires. Changing
this voltage changes the point on the waveform where the timebase starts.
Varying the oscilloscope trigger voltage point
•
•
It can be seen that by altering the trigger voltage, the position on the waveform is
varied.
The trigger slope, as the name indicates, determines whether the time-base sweep is
triggered on a positive or negative going edge or slope.
Oscilloscope trigger on positive & negative slopes
Oscilloscope trigger sources
The waveform on which the oscilloscope can trigger can be sourced in a variety of ways.
Sometimes having an external source for triggering can make the waveform more stable and
enable the waveform to be seen in a more stable form.
•
•
•
Signal channel: The most common source of the waveform used for providing the trigger
is the signal channel itself. On multiple channel scopes the trigger defaults to the A channel,
but normally it is also possible to trigger on other channels as well. Triggering may be
marked A / B channel, or equivalent
External source: On most scopes there is the possibility of selecting an external trigger
source. This can be very useful when a system is synchronised to an external signal. It is
normally possible to have the same control of trigger voltage and slope for these external
signals.
Video: The video trigger was widely used for analogue video and television applications.
The trigger circuit extracted the synchronisation, sync pulses that were embedded in the
analogue video signal and used this.
•
Line: Using the line trigger facility, the scope would trigger on the power input, or line
voltage waveform. This form of triggering was useful for detecting line associated issues.
Trigger hold-off
One capability that is particularly useful when triggering more complicated waveforms is
known as the trigger hold-off control.
It is probably easiest to explain the operation of the trigger hold-off in terms of analogue
scopes.
Probe calibrations:
1. Menguji probe osiloskop dalam keadaan baik
2. Menguji osiloskop juga dalam keadaan baik dengan menghasilkan
gelombang segiempat berfrekuensi 1kHZ dan Vpp =05V
Comparison between analogue & digital osiloskop
Analogue oscilloscope
Digital oscilloscope
Need a calibration before each experiment
No need calibration
User need to manipulate all the required
Automatic measurement for time, frequency
volt.div, time /div, vertical and horizontal
and voltage
knob to obtain suitable wave on screen
Reading accuracy depend on user ability to
More precise reading and Suitable for
collect and calculate final measurement
professional usage
Much cheaper than digital oscilloscope
Expansive
oscilloscope
LATIHAN:
Capacitance meter
A capacitance meter is a piece of electronic test equipment whose purpose is to measure
capacitance, mostly of discrete capacitors. The capacitance meter works based off of the
directly proportional relationship between capacitance and a time constant.
LCR meter
An LCR meter is a type of electronic test equipment used to measure
the inductance (L), capacitance (C), and resistance (R) of an electronic componenT
ESR meter
ESR meter is a two-terminal electronic measuring instrument designed and used primarily to
measure the equivalent series resistance (ESR) of real capacitors; usually without the need
to disconnect the capacitor from the circuit it is connected to
TRANSISTOR TESTERS
transistor testers are instruments for testing the electrical behavior of transistors and solidstate diodes.
There are three types of transistor testers each performing a unique operation.
•
•
•
Quick-check in-circuit checker
Service type tester
Laboratory-standard tester
FREQUENCY COUNTER
1. A frequency counter is an electronic instrument, or component of one, that is used for
measuring frequency. Frequency counters usually measure the number of cycles of
oscillation, or pulses per second in a periodic electronic signal
2. Frequency counters are test instruments used to provide very accurate
measurements of the frequency of a signal.
DC power supply
1. A direct current (DC) power supply is a device that converts alternating current (AC) to
direct current (DC), or from one voltage to another. Most electronic devices and circuits are
powered by a DC power supply.
2. The majority of DC power supplies are in the form of wall adapters. It plugs into a standard
AC outlet and outputs a fixed quantity of DC voltage, typically 5 or 12 volts.
3. Small electronic devices such as cell phones, digital cameras, and portable music players
are powered by wall adapters. Most computers and televisions use a type of DC power
supply known as an internal power supply. The device's internal power supplies convert AC
voltages to DC voltages, which are subsequently utilized to power the device's various
elements.
4. Precautions for using DC Power Supply:
a) Make sure the DC power supply is turned off and unplugged before attempting to
clean or service it.
b) Never use water or other liquids to clean the DC power supply. Use only a dry, lintfree cloth.
c) Do not attempt to open or disassemble the DC power supply. Doing so could result in
electric shock or personal injury.
d) Do not operate the DC power supply if it appears damaged or malfunctioning.
Contact the manufacturer for assistance.
e) Keep the DC power supply away from children and pets to prevent accidental
injuries.
f)
Store the DC power supply in a cool, dry place when not in use.
g) Follow all manufacturer's instructions when using the DC power supply.
h) Do not use the DC power supply if you are not familiar with its operation. Seek
professional assistance if needed.