075582814553
An oscilloscope is an electronic test instrument that displays voltage as it changes over time, allowing these details to be seen directly. Most modern oscilloscopes are digital instruments that sample the input signal, store the data, and reconstruct the waveform on the screen. Their measurement capability depends on factors such as bandwidth, sample rate, memory depth, vertical resolution, channel count, and the probe being used. Understanding these factors helps you choose the right oscilloscope and obtain measurements that accurately represent what is happening in the circuit.
Figure 1. Digital Oscilloscope Displaying Multiple Waveforms
An oscilloscope mainly measures voltage as it changes over time. From the displayed waveform, it can also determine important signal characteristics such as amplitude, frequency, period, rise and fall time, duty cycle, pulse width, and phase difference. It can also reveal problems that are difficult to detect with a basic multimeter, including noise, ripple, ringing, overshoot, glitches, and waveform distortion. These measurements help engineers check signal quality, verify circuit operation, and locate faults in electronic systems. [1]
An oscilloscope captures an electrical signal and converts it into a waveform that shows how voltage changes over time. First, the vertical system conditions the incoming signal and adjusts its amplitude using settings such as volts per division. The conditioned signal then reaches the analog-to-digital converter (ADC), which samples the voltage at specific moments and converts those measurements into digital data. [1]
Figure 2. Simplified Digital Oscilloscope Acquisition, Timebase, and Trigger Flow
The horizontal system, or timebase, controls when the ADC takes each sample and how much time is represented across the display. The sampled data is stored in acquisition memory as a waveform record. A suitable sample rate is important because insufficient sampling can miss signal details or cause aliasing. [1,4]
At the same time, the trigger system monitors the signal for a selected event, such as crossing a set voltage level. When that condition occurs, it establishes the waveform’s time-reference point. This helps keep repetitive signals stable on the screen and allows the oscilloscope to capture specific events consistently. [1]
Finally, the processor uses the stored samples to build the waveform shown on the display. Voltage appears on the vertical axis and time on the horizontal axis, allowing the signal’s amplitude, timing, shape, noise, and other characteristics to be examined and measured. [1]
An oscilloscope screen uses a grid called a graticule to display voltage on the vertical axis and time on the horizontal axis. By reading the waveform against this grid and using the volts-per-division and time-per-division settings, you can measure signal amplitude, period, frequency, and timing differences between channels. Figure 3 shows an example with two sine waves, where both channels use a vertical scale of 1 V/div and the timebase is set to 500 µs/div. [1]
Figure 3. Oscilloscope Screen Showing Voltage, Timebase, Amplitude, Period, Frequency, and Channel Delay Measurements
The vertical scale is expressed in volts per division (V/div). It shows how much voltage each vertical grid division represents. In Figure 3, both CH1 and CH2 are set to 1 V/div, so each vertical division corresponds to 1 volt. If a waveform extends three divisions from the zero-reference line to its peak, the peak voltage is:
Vpeak=3x1V=3V
Changing the V/div setting changes only the displayed height of the waveform on the screen. It does not change the actual signal. A smaller V/div value makes the waveform appear taller, which helps when examining small voltage changes.
The horizontal scale is expressed in seconds per division (s/div) and is often shown in milliseconds, microseconds, or nanoseconds per division. It tells you how much time each horizontal grid division represents. In Figure 3, the oscilloscope is set to 500 µs/div, so each horizontal division corresponds to 500 microseconds.
For example, if a waveform spans four horizontal divisions, the time represented is:
t=4×500 μs=2 ms
Reducing the time-per-division value zooms in on a shorter time interval, while increasing it shows a longer portion of the signal.
Waveform amplitude is measured by counting vertical divisions and multiplying by the V/div setting. When measuring from the lowest point of the waveform to the highest point, the result is the peak-to-peak voltage:
Vpp= Nvertical x Vdiv
In Figure 3, the waveform spans six vertical divisions from peak to trough, and the vertical scale is 1 V/div, so:
Vpp= 6 x 1V = 6V
For a symmetrical waveform centered around the zero-reference line, the peak voltage is half of the peak-to-peak voltage:
Vpeak = Vpp2 = 6 V2 = 3 V
This matches the measurement shown in the figure, where the waveform reaches 3 divisions above the center line and 3 divisions below it. In Figure 3, the dashed center line is intentionally defined as 0 V for this example. On a real oscilloscope, use the channel’s ground-reference marker and confirm the probe attenuation, coupling, and offset settings; the center graticule line is not automatically 0 V.
The period is the time required for one complete cycle of a waveform. To find it, measure the horizontal distance between two equivalent points, such as one peak to the next peak, and multiply by the time-per-division setting:
T=Nhorizontal x tdiv
In Figure 3, one complete cycle spans four horizontal divisions, and the timebase is 500 µs/div, so:
T=4×500 μs=2 ms
The frequency is the reciprocal of the period:
f = 1T
So, for the waveform in the figure:
f = 10.002 s = 500 Hz
This means the waveform completes 500 cycles per second. Digital oscilloscopes often calculate this automatically, but reading it manually helps confirm that the displayed measurement is correct. [1]
When two channels are displayed at the same time, you can compare their timing by measuring the horizontal separation between corresponding points on the two waveforms, such as their peaks or rising edges. The time difference is found by multiplying the number of horizontal divisions by the time-per-division setting:
Δt = Nhorizontal × tdiv
In Figure 3, Channel 2 is delayed by one horizontal division relative to Channel 1. Since the timebase is 500 µs/div, the delay is:
Δt=1×500 μs=500 μs
This type of measurement is useful for checking propagation delay, synchronization, and timing relationships between signals. If the signals have the same frequency, the measured time difference can also be converted into phase difference:
φ = ΔtT × 360°
Modern digital oscilloscopes also provide cursors and automatic timing measurements, but understanding the division-based method makes it easier to interpret what the screen is showing. [1]
Oscilloscopes can display many waveform shapes depending on the signal source and circuit behavior. As shown in Figure 4, common examples include sine, damped sine, square, rectangular, sawtooth, triangle, step, pulse, and complex waveforms. The waveform shape shows how voltage changes over time and can help reveal timing behavior, switching activity, distortion, transients, and noise.
Figure 4. Common Waveforms Seen on an Oscilloscope
A sine wave is a smooth periodic waveform commonly seen in AC power systems, oscillators, and many analog circuits. Its shape repeats continuously at a regular frequency. A damped sine wave also oscillates, but its amplitude decreases with time. This type of waveform can appear when a resonant circuit responds to a sudden disturbance or transient.
A square wave switches between two voltage levels with approximately equal high and low durations. It is commonly associated with digital clocks, logic signals, and switching circuits. A rectangular wave also switches between two levels, but the high and low durations are unequal. This difference is usually described by the waveform's duty cycle.
A sawtooth wave changes approximately linearly in one direction and then returns rapidly in the opposite direction. A triangle wave rises and falls at approximately constant rates, producing a more symmetrical shape. These waveforms are often used in timing circuits, waveform generators, modulation systems, and control applications.
A step waveform represents a transition from one steady voltage level to another. Engineers often use step signals to examine how a circuit responds to a sudden input change. A pulse is a temporary transition from one voltage level to another and back again. Oscilloscopes can measure pulse characteristics such as width, amplitude, rise time, fall time, and timing relative to other signals.
The complex waveform in Figure 4 represents a signal with multiple or rapidly changing components rather than one simple repetitive shape. Real electronic signals may contain switching activity, modulation, interference, noise, or several frequency components at the same time. These signals are especially useful to inspect with an oscilloscope because their time-domain behavior may not be obvious from a simple voltage measurement.
Waveform shape alone does not identify its source. Interpret a trace using the measurement location, voltage level, timing, probe loading, and expected circuit behavior.
Oscilloscopes are broadly divided into analog and digital types.
An analog oscilloscope continuously traces the input waveform and is useful for directly observing repetitive analog signals. However, it has limited waveform storage and analysis capability compared with modern digital instruments. A digital oscilloscope converts the input signal into sampled numerical data, allowing waveforms to be stored, processed, measured, and transferred to a computer. Digital instruments are therefore more practical for most present-day troubleshooting, design, and verification tasks. [1]
A digital storage oscilloscope (DSO) is the conventional form of digital oscilloscope. It samples the input signal, stores the samples in acquisition memory, and displays the resulting waveform. Because the waveform is stored digitally, a DSO can capture single-shot events and transients that would be difficult to examine with a traditional analog oscilloscope. DSOs are well suited to general electronics troubleshooting, multichannel measurements, pulse analysis, and observing events that do not repeat continuously. [1]
A digital phosphor oscilloscope (DPO) is designed to provide more information about how often different waveform events occur. It uses intensity or color grading so frequently occurring portions of a waveform appear differently from rare events. This makes DPOs useful for finding intermittent glitches, jitter, timing variations, and other infrequent signal behavior that may be harder to notice on a conventional DSO. [1]
A mixed signal oscilloscope (MSO) combines conventional analog oscilloscope channels with additional digital logic channels. This allows analog and digital signals to be viewed on the same time-correlated display. MSOs are particularly useful for embedded-system debugging, where an engineer may need to compare an analog sensor output or power rail with digital control, clock, or communication signals at the same time. [1]
A mixed domain oscilloscope (MDO) extends mixed-signal analysis into the frequency domain. In addition to analog and digital measurements, an MDO can include a dedicated spectrum-analyzer signal path for examining RF signals. This makes it useful when troubleshooting systems such as wireless devices, embedded radios, and RF-controlled electronics where analog, digital, protocol, and RF events need to be correlated in time.
A digital sampling oscilloscope is intended mainly for very high-bandwidth repetitive signals. Instead of relying on one real-time acquisition to reconstruct the entire waveform, sampling architectures can combine samples obtained from repeated occurrences of the signal. This approach enables extremely high effective timing resolution and bandwidth, making these instruments suitable for applications such as high-speed serial communication, optical testing, jitter analysis, and time-domain reflectometry. They are generally less appropriate for unpredictable single-shot events because the signal must repeat reliably for equivalent-time reconstruction. [1]
A USB or PC-based oscilloscope uses external acquisition hardware connected to a computer, while software on the PC provides the waveform display, controls, measurements, and analysis. These instruments can be compact and portable and can take advantage of a computer's large display, storage capacity, and processing resources. They are useful for laboratory work, education, field measurements, automated testing, and applications where portability is important.
However, USB or PC-based is a form factor and system arrangement rather than a separate acquisition architecture. A PC-based oscilloscope can itself be a DSO, MSO, or even a high-bandwidth sampling instrument, depending on its internal hardware. Current PC-based product families span a wide range of bandwidths, memory depths, channel counts, and sampling architectures.
Figure 6. Digital Oscilloscope with Connected Oscilloscope Probes
An oscilloscope probe is part of the measurement system and can affect both the circuit and the waveform being measured. Probe bandwidth, attenuation, input impedance, capacitance, grounding, and connection method all influence measurement accuracy and signal integrity. [2]
Passive voltage probes are commonly used for general-purpose measurements and normally require no external power. Many use 10X attenuation, which reduces the signal by a factor of ten while typically lowering capacitive loading and increasing the usable voltage range compared with a 1X probe. [2]
Figure 7. Typical 10X Passive Oscilloscope Probe
Passive probes are suitable for many ground-referenced analog and digital measurements. However, their input capacitance can distort fast edges and high-frequency signals, so the probe's bandwidth, voltage rating, and input characteristics must match the application. [2]
Active probes contain powered electronics near the probe tip and are designed mainly for high-speed, low-voltage signals. Their low input capacitance and high bandwidth reduce loading and help preserve fast rise times and small waveform details. [2]
Figure 8. Active Oscilloscope Probe for High-Speed Signal Measurements
Many active FET probes have lower maximum input-voltage and dynamic-range limits than passive probes. Their voltage rating, bandwidth, and operating range should therefore be checked before use. [2]
Figure 9. Differential Oscilloscope Probe and Measurement Accessories
A differential probe measures the voltage difference between two points without referencing either point directly to oscilloscope ground. It is useful for differential buses, high-side switching nodes, and power circuits. The probe should have suitable differential-voltage range, common-mode range, bandwidth, and common-mode rejection. [2]
Figure 10. Clamp-Style Oscilloscope Current Probe
A current probe allows an oscilloscope to display current over time. Some models measure AC only, while others measure both AC and DC. Clamp-style current probes are commonly used in power supplies, inverters, motor drives, and switching circuits without opening the conductor. [2]
Probe attenuation reduces the signal before it reaches the oscilloscope. A 1X probe passes approximately the full signal, while a 10X probe reduces it by a factor of ten. The oscilloscope must use the matching probe setting to display the correct voltage. [2]
Passive probes also need proper compensation. Using the oscilloscope's square-wave calibration output helps check this. Incorrect compensation can make square-wave edges appear rounded or overly peaked. [2]
A clamp current probe measures the net current enclosed by its jaws without electrically disconnecting the circuit. Clamp it around one conductor only; enclosing both the outgoing and return conductors normally causes their magnetic fields to cancel.
Using an oscilloscope correctly requires proper probe connection, scaling, time-base, and trigger settings. The following steps describe a basic ground-referenced voltage measurement using a passive probe.
Connect the probe to the oscilloscope and set the correct attenuation, such as 10X. Connect the ground clip only to circuit ground. On many bench oscilloscopes, the probe ground is connected to protective earth, so attaching it to a live or floating node can cause a short circuit. Use a suitable differential probe for floating or high-side measurements. [2,5,6]
Connect the probe to the oscilloscope's compensation output and observe the square wave. Adjust the probe until the waveform has a flat top and correctly shaped edges. Rounded edges indicate undercompensation, while excessive peaking indicates overcompensation. [2]
Connect the probe tip to the signal and keep the ground connection as short as possible. Long ground leads can add inductance and produce ringing. Make sure the signal remains within the voltage ratings of both the probe and oscilloscope. [2,5,6]
Adjust the V/div setting until the waveform fits clearly on the display. A smaller V/div value enlarges the waveform, while a larger value allows higher-voltage signals to fit on the screen.
Set the time/div control so one or several waveform cycles are clearly visible. Adjust the setting until the waveform is easy to inspect and measure. For manual period and frequency calculations from the graticule, see Section 3.
Select the measured channel as the trigger source and use an edge trigger for basic measurements. Choose the rising or falling edge and adjust the trigger level until the waveform appears stable. [1]
Once the waveform is stable, measure amplitude, peak-to-peak voltage, period, frequency, pulse width, rise time, or channel delay using the graticule, cursors, or automatic measurement functions. [1]
An oscilloscope, digital multimeter (DMM), and logic analyzer can all be used for electrical troubleshooting, but they provide different information.
| Feature | Oscilloscope | Digital Multimeter | Logic Analyzer |
| What it measures | Voltage waveform versus time; with suitable probes, can also measure current and other quantities | Voltage, current, resistance, continuity, and often capacitance, frequency, and other electrical quantities | Digital logic states and their timing |
| Time visibility | Excellent; displays waveform shape and changes over time | Limited; mainly displays numerical readings rather than waveform detail | Excellent for digital timing and state changes |
| Number of signals | Commonly 2–4 analog channels; some models provide more channels or additional digital inputs | Usually measures one primary signal or quantity at a time | Often monitors many digital channels simultaneously |
| Speed | High; suitable for fast edges, pulses, transients, glitches, and repetitive signals | Relatively slow compared with an oscilloscope; best for steady or slowly changing values | High-speed digital acquisition, depending on sample rate and instrument design |
| Measurement accuracy | Good waveform and timing accuracy, but generally not as precise as a quality DMM for steady DC measurements | Typically, best of the three for precise steady voltage, current, and resistance measurements | Optimized for determining digital states and timing rather than precision analog voltage measurement |
| Digital decoding | Many digital oscilloscopes can decode buses such as I²C, SPI, UART, CAN, and others, depending on model and options | Generally, not intended for protocol decoding | A major strength; designed for digital-state analysis and protocol decoding |
| Waveform shape | Shows amplitude, noise, ringing, overshoot, distortion, rise/fall time, and other analog details | Does not normally display the complete waveform | Shows digital high/low states but generally not the detailed analog shape of the signal |
Note: These instruments are complementary rather than direct replacements. A multimeter is best for precise steady-value measurements, an oscilloscope is best for viewing waveform behavior over time, and a logic analyzer is best for monitoring and decoding multiple digital signals.
• Bandwidth – The −3 dB frequency of the oscilloscope’s analog input response. At this frequency, a sine-wave amplitude is displayed at approximately 70.7% of its actual value. The oscilloscope-and-probe measurement system must provide sufficient bandwidth for the signal’s frequency content and edge speed.
• Sample Rate – The number of samples taken per second. A higher sample rate captures more detail from fast-changing waveforms.
• Record Length or Memory Depth – The number of sampled points the oscilloscope can store in one acquisition. More memory allows longer captures at high sample rates.
• Number of Channels – The number of signals that can be measured at the same time. Common oscilloscopes have two or four analog channels, while MSOs may include additional digital channels.
• Vertical Resolution – The ADC resolution, usually expressed in bits. Higher resolution can distinguish smaller voltage differences.
• Input Voltage Range – The maximum and minimum voltages the oscilloscope can safely measure. Probe attenuation must also be considered.
• Input Impedance – The electrical load presented by the oscilloscope input, commonly specified as resistance and capacitance.
• Rise Time – The fastest edge the oscilloscope can reproduce. For an approximately Gaussian response, oscilloscope rise time is about 0.35/BW; maximally flat responses may use about 0.4/BW
• Trigger Capability – Determines which signal events can start or stabilize an acquisition. Advanced triggers can capture glitches, pulse widths, protocol events, and other specific conditions.
• Time Base Range – Defines the range of time-per-division settings available for observing very fast or very slow signals.
• Measurement Accuracy – Includes vertical gain accuracy, time-base accuracy, and other specifications that affect the reliability of measured values.
• Probe Compatibility – The oscilloscope should support probes with the required bandwidth, attenuation, voltage rating, and interface.
• Connectivity – USB, LAN, Wi-Fi, or other interfaces can support waveform transfer, remote control, automated testing, and data storage.
• Protocol Decoding – Some digital oscilloscopes can decode interfaces such as I²C, SPI, UART, CAN, LIN, and other serial buses.
• Waveform Update Rate – Indicates how quickly the oscilloscope can acquire and display new waveforms. A higher update rate can make intermittent events easier to detect.
• Maximum Input Voltage – The highest permitted input under the specified coupling, impedance, frequency, and measurement-category conditions. Do not exceed the lower rating of the oscilloscope or probe.
• Vertical Sensitivity and Input Range – The available V/div and offset settings used to position and scale a signal. These settings are not the same as the maximum safe input voltage.
Most conventional bench oscilloscopes have their input ground connected to protective earth through the power cord. This means the probe ground clip is not equivalent to an isolated multimeter lead. Attaching it to a live or non-ground-referenced node can create a short circuit through earth, which may damage the circuit, probe, oscilloscope, or create a shock hazard. [2,5]
Always check the oscilloscope and probe maximum input ratings before making a measurement. For normal ground-referenced circuits, connect the probe ground only to the circuit ground. For floating nodes, high-side switching points, or measurements across two non-ground-referenced points, use a properly rated differential probe or isolated measurement method. Never disconnect the oscilloscope protective-earth connection as a workaround, because this can make exposed metal parts hazardous. [2,5,6]
Technical References
[1] Tektronix. “XYZs of Oscilloscopes.” Tektronix, 2023. Primer, Document No. 03W-8605-8.
[2] Tektronix. “ABCs of Probes.” Tektronix, 2024. Primer, Document No. 60W-6053-17.
[3] Keysight Technologies. “Evaluating Oscilloscope Bandwidths for Your Application.” Keysight Technologies, 2023. Application Note, Publication No. 5989-5733EN.
[4] Keysight Technologies. “Oscilloscope Sample Rates versus Sampling Fidelity.” Keysight Technologies, 2023. Application Note, Publication No. 5989-5732EN.
[5] International Electrotechnical Commission. “Safety Requirements for Electrical Equipment for Measurement, Control, and Laboratory Use – Part 2-030: Particular Requirements for Equipment Having Testing or Measuring Circuits.” International Electrotechnical Commission, 2023. IEC 61010-2-030:2023, Edition 3.0.
[6] International Electrotechnical Commission. “Safety Requirements for Electrical Equipment for Measurement, Control, and Laboratory Use – Part 031: Safety Requirements for Hand-Held and Hand-Manipulated Probe Assemblies for Electrical Test and Measurement.” International Electrotechnical Commission, 2022. IEC 61010-031:2022, Edition 3.0.
Catalogue
FPGA / CPLD
Memory
MOS 
MCU 
DSP
OCEP
Secondary 
Other