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1. Context of the Experiment

Before starting with all the experiments, it is essential to understand how to use the basic devices to measure any electric circuit: the multimeter and the oscilloscope. This introduction will help you to conduct the other experiments.

2. Learning Goals of this Experiment

• Knowing: Multimeter and oscilloscope.

• Abilities: Handling of multimeter, breadboard, and oscilloscope to measure electric circuits (voltage, current, resistance).

• Understand: Difference between circuits in parallel and series. How an electric signal is defined, utilizing the different functions of the oscilloscope.

3. Literature

[1] How to use a multimeter - Beginner's Guide - Random Nerd Tutorials (most of the following parts regarding the multimeter come from this reference)

[2] Datasheet of the multimeter MS0205

[3] 15 Multimeter Symbols Meaning, Function, and Usage

[4.1] Video on EDUX1052G oscilloscope (by iMEK) ← watch at least this one before attending the experiment!

[4.2] How to Use an Oscilloscope - Mega Guide - Keysight Labs (greater overview, contains sketches)

[5] User's guide for the EDUX1052G

[6] How To Use A Breadboard – The Beginner’s Guide

4. Basics / Fundamentals

4.1. Breadboard

The breadboard is a useful component for tinkering and prototyping. It allows you to quickly build an electrical circuit without soldering components together. It is infinitely reusable.

A breadboard consists of a perforated block in which each hole has a tinned spring clip to make good electrical contact with the tip of the component you are plugging in. Some of these holes are pre-connected to each other in a certain pattern. This makes it easy to connect components without soldering.

The breadboard usually consists of power columns and component areas. Typically, you use the columns on the sides to connect your power supply. And you use the rows in the middle to connect your components. In the power columns, the internal connection is vertical. This means that every hole in a column is connected. By default, the red line is the plus of the power and the blue line is the minus or ground. In the component area, the internal connection is horizontal. This means that for each row, all holes are connected. There is usually a gap in the middle of the board so that the power on the left and right are not connected. Similarly, columns A through E are not connected to columns F through J.

4.2. Multimeter

A multimeter is a measurement tool necessary in electronics. It combines three essential features: a voltmeter, ohmmeter, and ammeter, and in some cases continuity.

A multimeter allows you to understand what is going on in your circuits. Whenever something in your circuit isn’t working, the multimeter will help you troubleshoot. Here are some situations in electronics projects where you may find the multimeter useful:

• is the switch on?

• is this wire conducting the electricity or is it broken?

• how much current is flowing through this LED?

• how much power do you have left on your batteries?

These and other questions can be answered with the help of a multimeter.

You can find a wide variety of multimeters with different functionalities and accuracy. A basic multimeter costs about 5€ and measures the three simplest but most important values in your circuit: voltage, current, and resistance. However, you can guess that this multimeter won’t last longer and isn’t very accurate. The best multimeter for you will depend on what you intend to do, if you’re a beginner or a professional electrician, and on your budget. In this experiment, you will use a multimeter from EnovaLab [2], which costs about 30 €.

A multimeter is composed of four essential elements:

• Display: this is where the measurements are displayed

• Selection knob: this selects what you want to measure

• Ports: this is where you plug in the probes. They can vary depending on the multimeter you’re using, but there will always be at least a “COM” (or “-”) port, a current, and a voltage port.

• Probes: a multimeter comes with two probes. Generally one is red and the other is black. There isn’t any difference between the red and the black probes, just the color. But, assuming the convention:

  • The black probe is always connected to the COM port.

  • The red probe is connected to one of the other ports depending on what you want to measure.

You'll see various symbols around these components indicating the different functions that the multimeter can perform. Below is a table of the main symbols with their meaning.

4.2.1. Voltage measurement

You can measure DC voltage or AC voltage. It is necessary to set the type of voltage you want to measure (DC or AC). Depending on the multimeter, you will have to use the knob or another button for that. For the one you will be using, the position of the knob is the same for AC and DC, but you have to press the “SEL” button to switch from AC to DC or the other way around.

Similarly, some multimeters require you to select the voltage range you want to measure (such as 0.1 V, 1 V, 10 V, 100 V, 1000 V). However, the multimeter you will be using has an automatic range function, so you do not have to worry about that.

Here are the steps to measure a voltage:

1. Connect the black probe to the COM port of the multimeter.

2. Connect the red probe to the V socket of the multimeter.

3. Select the voltage measurement function with the knob. (If necessary: choose the range).

4. Choose the mode between DC and AC by pressing the SEL button.

5. Connect the other side of the red probe to the positive side of your component, which is where the current is coming from.

6. Connect the black probe to the other side of your component.

7. Read the value on the display. Be careful to also read the unit on the display, it can be in mV or V.

8. Disconnect the measuring tips from the measured object and turn off the multimeter.

For multimeters without automatic range: If you have to measure the voltage of something but don't know the range it falls under, test multiple ranges. If the range you picked is lower than the actual value, the display will show 1, indicating that the voltage is higher than the range selected. If you choose a range that is too high, you can often read the voltage value, but with less precision.

4.2.2. Current measurement

On most multimeters, it is necessary to set the range of the current to be measured (for example, μA, mA, or A). There are usually 2 different ports for this purpose and different positions of the knob. The different range settings on the multimeter give you different levels of accuracy. The multimeter can only display a certain number of characters, so the different ranges effectively determine how many characters are before or after the decimal point. You want to use the range that is closest to the measured value for the most accurate measurement, but the value you are measuring should not be greater than the measurement range.

The following table shows the current ranges of the multimeter you will use in your experiments:

Same as with voltage, you can measure current in either DC or AC form. It is therefore necessary to choose the type of current you want to measure. For the multimeter you will be using, the position of the knob is the same for AC and DC, but you have to press the “SEL” button to switch from AC to DC or the other way around.

Here are the steps to measure a current:

1. Connect the black probe to the COM port of the multimeter.

2. Connect the red probe to the μA / mA (up to 600 mA) or 10A socket of the multimeter depending on the range of current you want to measure.

3. Select the corresponding function with the knob:

   1. μA (up to 600 μA)

   2. mA (up to 600 mA)

   3. A (up to 10 A)

4. Choose the mode between DC and AC by pressing the SEL button.

5. Open the circuit at the point where you want to measure the current.

6. Connect the red probe to the lead of the previous component in the circuit (in the direction from positive to negative).

7. Connect the black probe to the lead of the next component in the circuit.

8. Read the value on the display. Be careful to also read the unit on the display.

9. Disconnect the measuring tips from the measured object and turn off the multimeter.

4.2.3. Resistance measurement

The multimeter is also capable of measuring the resistance of a component and in particular of resistors. To identify a resistor you can always check its color code (see table below), but this may take time and does not give the exact value of the resistor but its supposed value (due to the manufacturing tolerance). To check the value of the resistor quickly you can use the multimeter.

Here are the steps to measure resistance:

1. Connect the black probe to the COM port of the multimeter.

2. Connect the red probe to the Ω socket of the multimeter (It is the same as the one for the voltage).

3. Select the resistance measurement function with the knob, the one with the Ω symbol. (If necessary: choose the range).

4. Connect the other side of the red probe to one of the leads of your component.

5. Connect the black probe to the other lead of your component.

6. Read the value on the display. Be careful to also read the unit on the display.

7. Disconnect the measuring tips from the measured object and turn off the multimeter.

4.2.4. Continuity check

Most multimeters have a function that allows you to test the continuity of your circuit. This allows you to easily find faults such as faulty wires. It is also a good way to check if there is a connection between two points on the circuit.

Here are the steps to check for continuity:

1. Connect the black probe to the COM port of the multimeter.

2. Connect the red probe to the continuity socket of the multimeter, the one that looks like a speaker (It is the same as the one for the voltage).

3. Select the continuity function with the knob, the one that looks like a speaker. (The SEL button switches between the continuity check and the diode measurement.)

4. To check if the multimeter is properly set you can touch the two probes together. If it works, you will hear a continuous sound. If not, check your settings.

5. Turn off your system.

6. Connect the probes to the two points on the circuit where you want to check continuity.

7. If you hear a continuous sound, the two points are connected. If not, the two points are not connected. If the sound is not continuous, there is a bad connection.

8. Additionally, the resistance value appears on the display and some LEDs appear on top of it to show the continuity level.

9. Disconnect the measuring tips from the measured object and turn off the multimeter.

4.2.5. Summary

Type of measurement	Voltage	Current	Resistance	Continuity
Circuit configuration	Parallel	Serie	Parallel	Parallel
Ports of the multimeter		10A is used when measuring large currents, greater than 600mA µA / mA is used to measure smaller current
Setting of the multimeter

4.3. Oscilloscope

An oscilloscope is an electronic test instrument that graphically displays varying voltages of one or more signals as a function of time. Their main purpose is capturing information on electrical signals for debugging, analysis, or characterization. Modern devices support the analysis of captured information like amplitude, frequency, and others with a variety of inbuilt features and cursors for manual data range selection.

Depending on the design of the oscilloscope additional features can be found. These are an inbuilt function generator wired to a dedicated output as well as an external trigger input to name just two.

Whether or not an oscilloscope is suited for the desired task is defined by the four main factors:

1. Voltage input range

   1. Defines the maximum voltage levels the device is capable of measuring. If exceeded, the device might get destroyed.

2. Bandwidth

   1. must be at least two times the highest frequency component in your signal.

   2. lowest frequency at which a sampled sine wave is attenuated by 3 dB.

   3. circuits with switching components can require a different approach, see the English oscilloscope user manual (here: datasheets), page 134.

3. Sampling rate

   1. Should be at least four times the oscilloscope's bandwidth.

   2. actual sampling rate defined by the time of acquisition, e.g. 500 µs of data in 50,000 points of memory results in 100 MSa/s actual sampling rate.

4. Memory size

   1. defines how many samples can be stored.

   2. Affects the resolution of a captured signal within a predefined observation window (as explained above in 3.b.)

5. Resolution

   1. Resolution defined by the built-in ADC.

The main factors determining the price of an oscilloscope are the number of input channels, the memory depth, resolution, and the (maximum) sampling rate. The simplest versions at Conrad are available for less than 100 € and can rise to 40.000 € and more with a bandwidth of a few GHz and a maximum sampling rate of 10GSa/s to write millions of data points available in the device's storage.

5. Technical Basics & Preparations

5.1. Material

The following equipment and materials are needed for this experiment:

• Breadboard (general box)

• LED

• Battery

• Resistor

• Arduino (general box)

• Arduino IDE to flash the Arduino

• Jumper wires (general box)

• Multimeter (drawer of the working place)

• Oscilloscope (drawer of the working place)

• Computer (please bring your own laptop if you can)

  • ← download the Arduino code and flash it on the Arduino provided in the general box. You might need to flash it twice before it works properly.

5.2. How to program an Arduino

Unzip the aFunGen.zip and open the aFunGen.ino file.
Next check if the Arduino is detected by your computer and select it for the upcoming upload.
Depending on the version of the installed Arduino IDE, you have to do the following:

5.2.1. IDE version 2.x

1. The window in the top displays the type of the detected Arduino.

2. Click the drop down and select the Arduino. The Arduino is selected, as soon as it becomes written in bold letters:

3. Use the button with the arrow to upload the program to the Arduino:

4. You will get a notification in the right bottom of the IDE as soon as the upload is completed:

5.2.2. IDE version 1.x

In older versions, you need to select “Tools” (“Werkzeuge”)
1. The board is connected as soon as its name shows up next to the Port entry:

2. If it does not show, you need to select it from the list of available ports:

3. Upload the code to Arduino using the arrow button (“Upload” / “Hochladen”) in the top left corner:

4. You will get a notification as soon as the upload is done.

6. Experiment Procedure

Take your box and check its content.

6.1. Measure a battery’s voltage

To check if a battery is still working, you can check its voltage.

6.1.1. Set the multimeter to measure a voltage as explained before. Note: A battery provides a DC voltage.
6.1.2. Measure the voltage of the battery in your box. If you have a set of 2 batteries, please measure the voltage of the set and not of a single battery. ( 💾 save in app in the lab)

6.2. Measure a resistor’s resistance

6.2.1. Set the multimeter to measure a resistance as explained before.
6.2.2. Measure the resistance of the resistor in your box. ( 💾 save in app in the lab)

You can check the coherence of the value you measured with the color code of your resistor (see figure in the fundamentals part).

6.3. Check the continuity on a breadboard

6.3.1. Set the multimeter to check for continuity as explained before.
6.3.2. Check the continuity between different points on the breadboard. As the probes of the multimeter are too thick to go into the holes, you can make use of the wires available in the general box.

( 💾 save in app in the lab)

6.4. Measure the voltage in a circuit

Now you will measure the voltage drop across a resistor in a simple circuit. This example circuit lights up an LED.

6.4.1. Wire the circuit by connecting an LED to a battery through a resistor, as shown in the schematic:

The anode lead has to be connected to the rest of the circuit where the current comes from.

6.4.2. You should see the LED turning on. If not, your circuit is wrong, the LED is broken or the battery level is too low.
6.4.3. Set the multimeter to measure a voltage as explained before.
6.4.4. Measure the voltage drop across the resistor. ( 💾 save in app in the lab)

6.5. Measure the current in a circuit

6.5.1. Open the circuit you just built at a point where you will measure the current. The LED should turn off.
6.5.2. Set the multimeter to measure a current as explained before. Hint: the current is expected to be in the range of 20 mA.
6.5.3. Measure the current in the circuit. ( 💾 save in app in the lab)

6.6. Detect your first signal

6.6.1. Connect the Probe tip to the Demo terminal below the screen and the probe’s ground lead to the ground terminal next to it.
6.6.2. Use the white “Auto Scale” button on the top left of the control panel. You should see the following on the screen:

6.6.3. What is the maximum voltage of the signal? (💾 save in app in the lab)
6.6.4. What is the width of one peak? (💾 save in app in the lab)

6.7. Measure the switching behavior on the digital pin of an Arduino

In this task, you will determine the time it takes for two consecutive pin commands to be executed by the Arduino. Pin 7 will change from its initial state (LOW) to a logical 1 (HIGH) and back (check Arduino Code if you like to).

6.7.1. Connect the digital pin 7 to the oscilloscope using jumper wires from the general box. Don’t forget to connect the ground (labeled “GND” on the Arduino) to the ground clip of the probe.
6.7.2. Set the trigger to 3 volts to detect a signal (right bottom side of the control panel). Make sure the correct trigger source is set.
6.7.3. Use the “Single” knob in the top right area of the control panel to automatically freeze the screen as soon as a trigger event occurs. You will need to zoom into the lower µs/ on the horizontal axis before you see the desired signal. If you changed the zoom after the trigger event occurred, trigger the signal once more. You will see the resolution increase.
If you succeed, the signal below should show up on the scope.

6.7.4. What is the time it takes the Arduino to execute two consecutive commands on pin 7 (measure the first burst)? (💾 save in app in the lab)
6.7.5. What is the duration of the second “HIGH” signal?

6.8. Use the in-build Math function to determine the delay of switching processes

This task is set up to display a simple use of the math function to highlight differences in signals and how those could be measured. You will determine the delay of consecutive commands executed on the pins 7 and 8.

6.8.1. Connect a second probe to the digital pin 8 as done before (pin 7 remains connected to the first probe!).
6.8.2. Now switch the trigger source to pin 8 (if pin 8 is connected to input 2, a “2” should be selected as the trigger source) and trigger the signal.
6.8.3. Activate the “Math” function by pressing the transparent knob on the bottom left of the control panel (purple in the picture of the front panel above).
6.8.4. Select “-” as the operator you want to use to highlight areas where the signals from pin 7 and pin 8 are different. If everything is set up correctly you should see two rectangles of the same size (see below).

6.8.5. What is the time it takes the Arduino to execute two consecutive commands for pin 7 and pin 8 (delay between the two rising edges of pin 7 and pin 8)? (💾 save in app in the lab)

6.9. Read and evaluate PWM signals on an Arduino

You are going to capture and analyze two PWM signals from the pins 3 and 5.

6.9.1. Deactivate the “Math” function by pressing the purple button and connecting the probes to pins 3 and 5. The connection of one probe ground clip to the ground of the Arduino is of utmost importance as you will have disturbances on your signal otherwise. It might be wise to shift the signals vertical for better reading:

You now need to measure the periods of the two PWM signals as well as the duty cycle (percentage of a “high” signal compared to the duration of one cycle).

6.9.2. What is the frequency and the duty cycle of the PWM on pin 3? (💾 save in app in the lab)
6.9.3. What is the frequency and the duty cycle of the PWM on pin 5? (💾 save in app in the lab)

6.10. Read out digital communication using the analysis function of the oscilloscope

The final task shows how to use the “Analyze” functions built into the oscilloscope. You will use the “Serial Bus” feature to extract information on data sent via UART from the “0->RX” pin of the Arduino.

6.10.1. First, you can deactivate the measure functions and cursors as they are not used in this section.
6.10.2. Connect pin 0 (labeled “0->RX” on the Arduino) to one probe and Pin 1 (labeled “1<-TX”) to the other probe.
6.10.3. Set up the serial bus analyzer

6.10.3.1. Activate the “Serial Bus” feature using the “Analyze” button next to the previously used “Meas” and “Cursors” buttons. Now use the menu to set the following:
6.10.3.2. Features → “Serial Bus”
6.10.3.3. Mode → “UART/RS232“ (we are going to analyze a UART transmission)
6.10.3.4. Bus Config → “#Bits“: 8 | “Parity“: “None” | “Baud Rate”: “9600 b/s” | “Polarity”: “Idle high” | “Bit Order”: “LSB”
6.10.3.5. Settings → “Base“: Hex

6.10.4. Set up the trigger to display the UART signal coming from the Arduino.

If everything is set up correctly, you should get a similar view as below, if you don’t, try to set the vertical and horizontal zoom to the same as in the picture (top row above the table in the picture):

6.10.5. What is the first hex number transmitted after the 1-2-3 sequence? (💾 save in app in the lab)
6.10.6. What is the hex number transmitted after the second 1-2-3 sequence? (💾 save in app in the lab)

7. Evaluation of Experiment Results

App

Just as an information, you can see here an overview of the app where you will have to enter your results: