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Using the Oscilloscope
The built-in oscilloscope is a two-channel digital storage oscilloscope (DSO) for seeing how voltages change over simulated time.
A multimeter answers “What is the voltage now?” An oscilloscope answers “What shape does this voltage make over time, how often does it repeat, and what happened before and after an edge?”
The scope is available in the full workbench and interactive article embeds. This guide starts with the reason for using one, then explains every control and a practical workflow.
Use the oscilloscope when a single voltage reading does not tell the whole story. Typical uses include:
- confirming that a clock is running
- measuring frequency, period, and duty cycle
- comparing an input with an output
- seeing whether a flip-flop divides a clock correctly
- watching counter stages and pulse trains
- observing RC charge and discharge curves
- finding a pulse that is too short for a multimeter to reveal
- examining propagation relationships between two signals
- locating glitches or unexpected transitions
A logic analyzer is best for many digital channels and state relationships. An oscilloscope is best when voltage shape, timing, level, or the relationship between one or two signals matters.
- Select Oscilloscope in Desk tools.
- Select CH1, then select the first circuit point to observe.
- Select CH2, then select a second point if needed.
- Select Ground and place it on the circuit reference, normally the power-supply negative terminal or breadboard ground rail.
- Press Run.
Both channels are measured relative to the one common Ground probe. A misplaced ground therefore shifts both readings. The yellow, blue, and white probe markers show the exact selected points.
Select any probe button to move that probe. The panel itself can be moved by dragging the Oscilloscope title bar. Instrument state and probe positions are temporary bench tools and are not stored in the project file.
The screen is divided into ten horizontal time divisions and eight vertical voltage divisions.
- Yellow is CH1.
- Blue is CH2.
- The voltage numbers on the left belong to CH1.
- The voltage numbers on the right belong to CH2.
- The colored side markers show each channel's 0 V reference.
- The labels across the top show time.
- The dashed vertical marker identifies the trigger position.
With a valid trigger, 0 s is the trigger event. Negative time occurred before the trigger and positive time occurred after it. In Roll mode, the right edge represents now and older data lies to the left.
The rows below the screen show the latest channel voltages and automatic measurements:
- Vpp: peak-to-peak voltage, or highest value minus lowest value
- Avg: average voltage over the captured record
- Freq: cycles per second
- Period: time required for one cycle
- Duty: percentage of a complete cycle spent above the measurement threshold
Duty cycle is calculated from complete cycles so partial pulses at the edges of the screen do not distort the answer.
Time/div controls how much simulated time one horizontal grid division represents. The whole screen covers ten times that value.
- Select − beside Horizontal to zoom in. Less time is visible and edges spread farther apart.
- Select + to zoom out. More time and more cycles are visible.
- Select an exact value from the time/div menu.
A useful starting point is to show two to five complete cycles. Zoom in to inspect an edge or pulse. Zoom out to compare slow behavior or reveal a waveform that appears to be a flat line.
If the signal is 1 Hz, one cycle takes about one second. At 250 ms/div, the ten-division screen spans 2.5 seconds and should show roughly two and a half cycles.
V/div controls how many volts one vertical division represents.
- Select − beside Vertical to use fewer volts per division and make the waveform taller.
- Select + to use more volts per division and make the waveform shorter.
If a waveform is clipped at the top or bottom, use a larger V/div value or move its vertical position. If it is too short to read, use a smaller V/div value.
Changing V/div changes only the display scale. It does not change the circuit voltage.
Each channel has its own vertical offset field, measured in divisions.
- Positive values move that trace upward.
- Negative values move that trace downward.
Offsets move only the drawing and the channel's colored 0 V marker. They do not change the signal or its measured voltage.
For two overlapping traces, try CH1 at -2 div and CH2 at +2 div, then adjust to taste. Each channel moves independently. You can also clear a channel's checkbox to hide it temporarily.
DC coupling displays the complete voltage, including its DC level. Use DC coupling for logic signals, supply rails, transistor bias, and whenever the absolute voltage matters.
Display-only AC coupling removes the average level so a changing component riding on a large DC offset is easier to see. It does not modify the circuit. Do not use the AC-coupled drawing to determine the original absolute DC level.
Imagine taking many photographs of a repeating waveform at random times. The edge would appear in a different horizontal position in every picture, so the trace would seem to slide or jump.
A trigger tells the scope which recognizable event should be placed at a fixed position. Repeated acquisitions align on that event, making the waveform appear stationary even while the circuit keeps running.
The trigger controls are:
- Source: CH1 or CH2, the signal examined for the trigger
- Edge: rising or falling
- Level: the voltage that the selected edge must cross
- Trigger position: where the event appears horizontally
Moving the trigger position right reveals more history from before the trigger. Moving it left reveals more behavior after the trigger.
For a 0–5 V digital clock, a rising trigger near 2.5 V is a useful starting point. For a TTL output that reaches only about 3.4 V, make sure the trigger level is below the high value and above the low value.
If the scope never obtains a stable trigger:
- Verify that the trigger source is the channel carrying the changing signal.
- Put the trigger level between that signal's low and high voltages.
- Confirm that the chosen rising or falling edge actually occurs.
- Start in Auto mode before trying Normal mode.
Auto is the best starting mode. A valid trigger produces a stable, edge-aligned display. If no trigger arrives, the scope eventually forces a complete free-running acquisition so a DC level or unfamiliar signal is still visible.
Use Auto while connecting probes, finding a signal, and setting the scales.
Normal updates only when the requested trigger occurs. Use it when a specific event matters and you do not want unrelated forced acquisitions.
An incorrect trigger setting can leave Normal mode waiting with no update. That is expected behavior: the requested event has not occurred.
Roll is a continuous chart-recorder view. New data appears at the right while older data moves left.
Roll is useful for slow clocks, RC charge and discharge curves, switch presses, sensor changes, and other low-frequency events where continuous movement is clearer than repeated triggered frames.
Roll motion is refreshed independently from the event-driven electrical sampling. This allows a slow clock to scroll smoothly without inventing transitions between real simulator events.
- Hold freezes the current capture while the circuit continues to run. Select Resume to acquire again.
- Clear removes the captured history and begins a fresh acquisition.
- Auto (the button, not the trigger mode) selects useful time/div and volts/div values from the captured waveform.
- Cursors enables T1/T2 time markers and V1/V2 voltage markers.
Use the cursor delta readouts to measure a pulse width, propagation delay, rise interval, period, or voltage difference manually.
The display frame rate is how often the screen is redrawn. The electrical sampling history is the sequence of simulator events captured by the scope.
Chip Hippo records simulator events, including transitions that occur between display refreshes, and resamples the acquisition into screen columns. A slow or busy display therefore does not determine the electrical sample history.
At very slow signal rates, the waveform itself changes only occasionally. Smooth Roll motion can make time visibly advance, but it should not add electrical edges that did not happen in the simulated circuit.
Open /embed/oscilloscope-demo. CH1 is connected to a nominal 1 Hz clock. CH2 is connected to a 74LS74 flip-flop wired as a divide-by-two stage.
Expected results:
- CH1 is approximately 1 Hz with a period near 1 second.
- CH2 toggles on each selected CH1 edge, so it is approximately 0.5 Hz with a period near 2 seconds.
- CH2 may show a TTL high near 3.4 V under Spice Lite rather than reaching the full 5 V supply.
- Both signals should have a duty cycle near 50%.
- CH2 should complete one cycle for every two CH1 cycles.
Use Auto mode with CH2 as the trigger source for a stationary comparison. Use Roll to watch both traces move continuously. Separate the traces with their independent vertical offsets when they overlap.
- Connect Ground, then CH1 and optionally CH2.
- Run the circuit and begin in Auto trigger mode.
- Set V/div so each waveform fits vertically.
- Set Time/div so two to five cycles are visible.
- Choose the channel and edge that represent the event of interest.
- Put the trigger level between that signal's low and high voltages.
- Separate the traces with channel offsets.
- Use Hold and Cursors for a close measurement.
- Switch to Roll when continuous slow-time movement is more useful than a stationary trigger-aligned waveform.
Run the circuit, verify all three probes, enable the channel, press Clear, and try Auto trigger mode.
The node may truly be DC, the circuit may not be switching, or the time/div setting may show only one portion of a long cycle. Zoom out horizontally and verify the node with the multimeter.
Check trigger source, edge, and level. Make sure the level lies between the signal's low and high voltages. Use Auto mode before Normal.
Zoom out horizontally to include more periods. A square wave cannot look repetitive unless the captured time window contains several edges.
Increase V/div, change that channel's vertical offset, or use Autoscale.
Give CH1 and CH2 different vertical offsets. The movement is display-only and does not change the measurements.
That is intentional. Roll continuously moves through time. A correctly triggered Auto or Normal trace remains stationary so repeated waveforms can be inspected.
The visible acquisition does not contain enough complete edges or cycles. Zoom out or allow the scope to acquire longer.
The scope does not currently model probe loading, input impedance, analog bandwidth, noise, probe compensation, hardware sample-rate selection, XY mode, protocol decoding, or FFT analysis.
Spice Lite supplies calculated node voltages. Digital-only runs fall back to nominal 5 V HIGH and 0 V LOW.
Next: Using the Multimeter