This free online oscilloscope runs in your browser. A built-in signal generator creates a sine, square, sawtooth or triangle wave, and the scope screen displays it live, so you can see how frequency and amplitude change the waveform. It is a learning and demonstration tool: it displays the signal it generates and does not measure external circuits.
How to use the online oscilloscope
- Press ON / OFF to start the generator and the scope.
- Choose a waveform, then move the Frequency and Amplitude sliders.
- Set Time / div so one or two cycles fill the screen, and Volts / div so the wave fits vertically.
- Leave Trigger on for a steady picture. Press Hold to freeze the trace and count divisions.
- Untick Speaker sound if you only want to look at the signal.
How to read frequency and amplitude
Count divisions on the grid and multiply by the control setting:
- Period T = (divisions for one cycle) x (Time/div). Frequency f = 1 / T.
- Peak-to-peak voltage Vpp = (divisions from bottom to top) x (Volts/div). The peak value is half of that.
The readouts under the screen show the same values calculated from the signal, so you can check your own reading.
Waveform formulas
For a wave with peak amplitude A, frequency f and period T = 1/f:
| Waveform | Equation (for the shape) | RMS value (ideal) |
|---|---|---|
| Sine | y(t) = A sin(2 π f t) | A / √2 = 0.707 A |
| Square | y(t) = +A for the first half of T, -A for the second half | A |
| Sawtooth | ramps from -A to +A over T, then drops back | A / √3 = 0.577 A |
| Triangle | ramps -A to +A and back over T | A / √3 = 0.577 A |
Worked example
Set the waveform to Sine, frequency to 1000 Hz, amplitude to 0.5 V, Time/div = 0.2 ms and Volts/div = 0.2 V.
- Period T = 1 / 1000 Hz = 1 ms, which is 1 ms / 0.2 ms = 5 divisions per cycle.
- Vpp = 2 x 0.5 V = 1.0 V, which is 1.0 / 0.2 = 5 divisions from bottom to top (peak = 2.5 divisions above centre).
- Vrms = 0.5 / √2 = 0.354 V, which is what the readout shows for a sine wave. For ideal waveforms a square wave would give 0.5 V and a sawtooth or triangle 0.289 V.
Limits of this tool
- It shows the signal made by its own generator. It cannot probe a real circuit.
- Frequency range is 20 Hz to 2 kHz. The browser audio sample rate (usually 44.1 or 48 kHz) limits what any browser scope can show.
- Square, sawtooth and triangle waves are band-limited by the browser, so small ripples on the edges are normal and the Vrms readout for these waves can be a little below the ideal value in the table.
- Amplitude is normalised: 1.0 on the slider equals 1 V on the screen scale, not a physical voltage.
Frequently asked questions
Is this a real oscilloscope?
No. It is a software simulation that draws the generated waveform on a scope-style screen. It is useful for learning how time/div, volts/div, trigger, frequency and amplitude work.
What is the maximum frequency it can display?
The generator runs up to 2 kHz. Higher frequencies are not useful here because the browser audio sample rate and the screen resolution limit the detail.
Can I measure an external signal from a microphone or line-in?
Not in this version. It displays its own generator. To look at real circuits you need a hardware oscilloscope or a sound-card scope program.
Why does my waveform look unstable or keep moving?
Turn Trigger on. The scope then starts each sweep at the same point of the wave. You can also press Hold to freeze the screen.
Why does the square wave show ripples?
Browsers create square and sawtooth waves with limited bandwidth to avoid aliasing, so you see small overshoots near the edges.