How to use an oscilloscope

Максим Исаев
Reading time: 12 min
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An oscilloscope is a digital or analog device designed to visually monitor the waveform of voltage and currents. Any electronics repair technician or engineer should be able to use the Oscilloscope to perform diagnostics.

The purpose of the oscilloscope

For the development and repair of modern electronic equipment, specialized knowledge in the field of electronic circuit design is needed. When designing or researching any circuit, it is necessary to take measurements. Since most circuits have a pulsed mode of operation, the devices must correspond to the technique under study. 

If before that we could freely manage with a multimeter, measuring the necessary values ​​\u200b\u200bof currents and voltages, then this will not be enough when diagnosing modern electronics. Since, in addition to the values ​​measured by the multimeter, it is necessary to visually control the signal shape of the device or circuit section that is being studied. 

In this case, a device called an oscilloscope is used. This device visually shows what processes occur in the electrical circuit at a certain point in the study. In practice, you can learn how to use the Oscilloscope by completing full-time training in the Electronics and Circuit Engineering program at Bgacenter.

sualization of processes using AKIP-4115/4A
Visualization of processes using AKIP-4115/4A

Oscilloscopes are of two types:

  • analog
  • digital

The development of electronic technology has supplanted analog, and digital has gained particular popularity among electronics engineers and novice radio amateurs. Due to their ease of use, as well as minimal preparation for work. These devices have great functionality, many useful features that are not available in analog devices. When repairing and tuning the APW8 power supply, it is necessary to use an Oscilloscope to visually control the amplitude and duration at the inputs of the field-effect transistors of the PFC stage and the final stage.

An oscilloscope is practically the same voltmeter where voltage is measured, so the device is connected in parallel to the section of the measured circuit, or in parallel to the power source. If you apply Ohm’s law, you can see the shape of the current. To do this, it is necessary to apply a resistance of 1 ohm, and when dividing the voltage by a resistance of 1 ohm, we get the current strength and its shape.

Setting up the oscilloscope

In this manual, we will consider all examples using the AKIP-4115/4A digital oscilloscope.

To use the device, it must be connected to the mains using the power cord supplied with the device.

Next, on the top of the case, you must press the button, wait for a while when the oscilloscope program loads. A screen saver with the name of the device will appear on the screen. After loading the operating system of the device, the display will light up (horizontal line on the screen of the device).

АКИП-4115/4А
AKIP-4115/4A

Since the Oscilloscope is a two-channel instrument, the first channel is enabled by default. Key CH 1 on the front panel, marked in yellow. The channel is highlighted, and the yellow line is also lit on the device screen. 

At the bottom of the control panel there is a high-frequency BNC connector (Bayonet Neill-Concelman), also yellow, which corresponds to the highlighted line on the oscilloscope screen. For the second channel, blue color is used, this is due to the convenience in operation while simultaneously observing the signal in the device under study with an oscilloscope.

Channel 1
Channel 1

For further work, you need to go to certain settings of AKIP-4115/4A. By default, a certain mode of operation can be set, for example, set by the manufacturer (interface language, time, settings values). To do this, this device has a specialized menu that has 6 independent function buttons located in the upper part of the tuning block in two rows.

The top row has keys:

  • Cursors
  • Collection of information
  • Zap. call
Top row of menu buttons 
Top row of menu buttons 

The bottom row has keys:

  • Measurement
  • Display
  • Utilities
Bottom row of menu buttons
Bottom row of menu buttons

To the left of this menu is the “SETUP” knob, which is necessary for setting the necessary parameters of the device in the corresponding MENU.

 Control knob
Control knob

When you press the “Utilities” button on the right side of the instrument screen, a 4-page menu appears. The topmost key “Menu On/Off” can remove the menu from the instrument screen when pressed. At the bottom of the block of buttons located on the screen panel, there is a “Print” button. With which you can write data from the oscilloscope screen to a flash drive.

Pressing the Menu On/Off key again will reappear the menu on the screen. 4-page menu, you can switch by pressing the fifth key from the top.

Menu Button ON/OFF
Menu Button ON/OFF

When you select the first page of the menu, you can use the “1” key to turn on the “STATUS” submenu, while information about the status of the device appears on the oscilloscope screen. This submenu can be exited by pressing the “Single” key.

 Device status
Device status

The submenu key “2” controls the muting and enabling of the beeper.

Key “3” displays the frequency of the measured signal.

Button “4” allows you to select the interface language.

Pressing the “5” key turns on the second page of the submenu. In this tab, by pressing the “1” button, self-calibration is performed. 

In Self Calibration mode, disconnect all probes and cables from the instrument. Then press the “Single” button, and a green scale appears, which is filled. After completion of Self-calibration, press the “Single” button. To exit the Self-calibration mode, press the “START/STOP” key.

Button Once
Button Once

“Self-test” mode. Pressing the “2” key opens a submenu corresponding to the buttons:

  • 1 – Screen Test. When this key is pressed, the screen turns red. Further pressing the “Single” button, the screen color can change to green and blue. This function helps to control the presence of primary colors RGB (red, green, blue). Exit this menu by pressing the “START/STOP” button.
  • 2 – Keyboard Test. By pressing this key, you can test the operation of all keys. In this case, the corresponding button on the screen will change color to green. What does it say about the correctness of the keys.
  • 3 – Test LED (LED Test). Checking the functionality of the button illumination.

Exit this submenu by pressing the “Utilities” button.

Utilities
Utilities

Page 3 submenu. Correspondence of buttons to settings:

  • 1 – Software update
  • 2 – “Advanced / Contra” using additional settings
  • 3 – “Record” – writes data to the required media, in accordance with the selected submenu
  • 4 – “Port settings”

Page 4 submenu. Correspondence of buttons to settings:

  • 1 – LED longevity mode
  • 2 – Registrar

Display” – main menu key

Pressing this button displays the following submenu items:

  • 1 – “Vector”
  • 2 – “Afterglow”
  • 3 – “Beam brightness”
  • 4 – “Grid brightness”

By pressing the “1” key, we can see the oscilloscope line either as dots or as a straight line (vector).

By pressing the “2” key, we select the duration of the screen glow after the measurement. From 1 second to infinity.

By pressing the “3” key, we can adjust the brightness of the beam with the “Setting” knob.

By pressing the “4” key, we can adjust the brightness of the coordination grid, for ease of use.

Exit this menu by pressing the “Utility” key

Measurements” – main menu key

Clicking this button opens five kinds of submenus:

  • 1 – Voltage. Channel source selection. Select the type of voltage measurement.
  • 2 – Time. Also channel source selection and duration type (frequency)
  • 3 – Delay.
  • 4 – All measurements. Channel, voltage and time. Three characteristics are simultaneously displayed on the screen.
  • 5 – Delete measurements.

Cursors” – main menu key

Sets measurement limit lines for amplitude and frequency

Information collection” – main menu key

Sample mode is used

Record/Recall” – main menu key

Switches the oscilloscope mode when the first key is pressed to the factory settings.

Initial settings” takes the oscilloscope to the user’s initial settings

Help” – pressing this button brings up the help menu. The movement is carried out using the buttons 1-5.

Start/Stop” – used to stop the signal under test. To measure its duration and amplitude.

AUTO” – automatically finds the investigated signal applied to the probes of the oscilloscope, for its further study.

The vertical sweep control of the first channel (yellow) is designed to select the optimal amplitude value for signal research.

Beam offset slider in vertical direction.

What does an oscilloscope measure?

An Oscilloscope is used to fully diagnose an electronic device.

Using an oscilloscope, you can measure the following parameters:

  1. The maximum amplitude of any signal
  2. View voltage and current plot
  3. Measure signal frequency
  4. View signal phase
  5. Measure DC voltage

The amplitude of the signal is the maximum value that is given by the generator during its operation. If we measure with a multimeter, then we see the effective value of current or voltage. Which is often not enough when designing or repairing electronic devices. 

Therefore, in this case, it is advisable to use a multimeter that measures the maximum amplitude values. An oscilloscope is often used for this purpose. For example, when considering a sinusoidal voltage of an electrical network through a step-down transformer at the output of a diode bridge without a smoothing filter capacitor.

Signal amplitude
Signal amplitude

A voltage or current diagram is an oscillogram, that is, an image on the oscilloscope screen applied to the input of the device of any electrical signal under study. Measurements can be carried out at any control point of interest to us and compared with the manufacturer’s data.

Plot of sinusoidal mains voltage
Plot of sinusoidal mains voltage

Signal frequency – the value of the signal under investigation in the time range along the X axis of the oscilloscope. Since this signal is measured in time (sec, milliseconds, microseconds), the frequency is the reciprocal of time. Therefore, to find the frequency, it is necessary to apply the formula: 

f = 1/T 

where: 

f is the frequency, in Hz

T – time, in S

Square waveform frequency
Square waveform frequency

Signal phase – measured using two channels. One signal under study is fed to one input, another signal is fed to the second input at the same frequency. The shift of signals on the screen of the device in time is the phase.

DC voltage measurement. Using the device, you can measure not only the amplitude variable value, but also the constant component of the voltage.

Oscilloscope without input signal
Oscilloscope without input signal

Measure the voltage of a DC source. The photo shows a noticeable rise of the horizontal bar up relative to the original value. According to the coordination grid Volts/div on the Y-axis, you can calculate the actual voltage at the output of the power supply.

DC voltage measurement
DC voltage measurement

How an oscilloscope works

The sequence of work with the oscilloscope:

  1. Connect the Oscilloscope to the mains.
  2. According to the instructions, select the appropriate settings in the menu items (language, time, etc.).
  3. Calibrate the instrument.
  4. Connect the high frequency BNC test leads to the appropriate connectors as marked.
  5. Start taking measurements by attaching the probe to the test point on the electronic board.
  6. If the signal under test is not displayed on the oscilloscope screen in manual mode, you must press the “AUTO” button. In this case, the device will show the signal under study.
  7. In the case when the signal diagram does not fit on the screen, it must be held with the “START / STOP” button, then, using the vertical and horizontal gain controls, bring the picture to the optimal display.
  8. When working with the oscilloscope, observe safety precautions. This is especially true when repairing the hot part of the switching power supply, tied to the electrical network. In this case, for complete safety, it is better to use an isolating transformer.

How to use an oscilloscope

Before you start using the Oscilloscope, it is important to determine what signal can be measured by the device in amplitude at a given point. This is necessary in order to avoid damage to the device. According to the instructions, set the maximum value of the voltage V / Division on the device according to the Y sweep. And according to the X sweep, the expected signal frequency. 

Only after that we connect the device to the appropriate control point for measurements. Then analyze the resulting stress diagram. For ease of reference, there are offset knobs:

  • along the Y axis – vertical deviation
  • X-axis – horizontal deviation

Use these controls to shift the resulting image to the origin, for ease of reference. There is a coordinate grid along the ordinate and abscissa (Y,X) axes. It is tied to the corresponding conditional values. According to the selected values, you can calculate the resulting voltage value in volts and time in seconds. To find the frequency, it is necessary to convert time into frequency, according to the formula f = 1/T.

Measuring a signal from a PWM controller (video)

For example, let’s take a board from a working TV and see the output pulses from the PWM controller in various operating modes:

  • in standby mode – when the TV is turned on, before pressing the power buttons
  • in operating mode – after pressing the power button (or what is the same under load)

 

It is convenient to use an oscilloscope to study the electrical circuit in the case when the PWM controller would be out of order. If there was power on the PWM controller, there would be no output pulses. And there would be some tension. And this, in turn, indicates a malfunction of the PWM controller itself or its circuits.

Findings

  • Learning how to use an oscilloscope is necessary for every electronics engineer and novice radio amateur involved in the development, production, configuration, diagnostics and repair of electronic devices.
  • It is important to be able to analyze the results obtained, based on an understanding of the operation of electronic components.
  • An oscilloscope is a complex device, but learning how to use it is not difficult.
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