OSC-2 · FG-2

Operating manual — OSC-2 oscilloscope and FG-2 function generator

The OSC-2 simulates a classic analog dual-trace oscilloscope with a dual (A and delayed B) time base. The FG-2 is a two-channel function generator. Both run in the browser; the scope inputs can also be connected to the computer's or phone's sound card. Panel labels are in English, as on most instruments; this manual names every control exactly as it is printed on the panel.

Quick start

  1. The instrument starts switched on (POWER lamp lit). CH1 shows the sine wave of generator output 1, CH2 the square wave of output 2.
  2. If you see no trace: set trigger MODE to AUTO, check that COUPLING is not at GND, turn INTENSITY up and bring the trace back with POSITION.
  3. Choose VOLTS/DIV so that the signal fills four to six divisions vertically, and A TIME/DIV so that one to three periods are visible.
  4. For a stable picture set the trigger SOURCE to the channel carrying the signal and turn LEVEL until the TRIG'D lamp lights.
  5. The Presets buttons under the instruments set up typical measurements in one click; the readings cards show peak-to-peak value, RMS value, mean value and frequency.

Operating the controls

Rotary knobs
Drag up or to the right to turn clockwise (hold Shift for fine adjustment), use the mouse wheel, or the arrow keys once the knob has focus. Clicking a marking on the scale turns the knob there; a double-click returns it to its default setting. While you turn a knob, a small label shows its exact value.
Rotary switches
VOLTS/DIV, A TIME/DIV, B TIME/DIV and WAVEFORM click into fixed positions (detents). The selected position is printed in red.
Toggle switches
Click a position in the slot to move the lever there; clicking the lever itself moves it one step. You can also drag the lever, use the mouse wheel or the arrow keys, or click the position label. A crossed-out label means that position is not available in this browser or view; the reason appears in a small bubble under the switch.
Push buttons
Latching buttons (MODE, ×10, POWER) stay pressed and light their lamp. SINGLE RESET is momentary.

Display section

INTENSITY
Brightness of the trace. Keep it no higher than needed: on a real cathode-ray tube a bright, stationary spot can burn the phosphor.
FOCUS
Sharpness of the trace (sharp — medium — blurred).
PERSISTENCE
Simulated afterglow of the phosphor (0–97 %). Long persistence shows slow sweeps and the spread of noisy signals; short persistence gives a crisp picture of fast-changing signals.
POWER
Switches the oscilloscope on and off; the trace fades out when switched off.
Z INPUT
Intensity modulation (Z axis). Source: OFF, GEN 1, GEN 2 or AUDIO (mono mix of the audio input). 0 V leaves the brightness unchanged, +5 V blanks the beam completely, negative voltage brightens it (up to twice at −5 V). Works in Y-T and X-Y modes.

The graticule has 10 × 8 major divisions with 0.2-division minor marks on the centre lines. The dashed lines marked 0 %, 10, 90 and 100 lie 2.5 and 2 divisions above and below the centre: they serve rise-time measurements (see Measurement tips).

Vertical system (CH1, CH2)

VOLTS/DIV
Deflection coefficient, 10 mV/div to 5 V/div in 1-2-5 steps. Values printed in dark blue are in volts, light blue ones in millivolts. Turning clockwise makes the channel more sensitive.
POSITION ↕
Vertical shift of the trace, ±4 divisions.
COUPLING
DC: the full signal including its DC component. AC: the DC component (mean value) is removed. GND: the input is disconnected and grounded; the trace shows the 0 V reference line — use it to set the zero level before measuring.
INPUT
Signal source of the channel: GEN 1 or GEN 2 (either generator output; both channels may show the same output), AUDIO IN (microphone or line input) or AUDIO OUT (the sound the computer is playing). See Live audio.
MODE
CH1 or CH2 alone; DUAL: both channels; ADD: the algebraic sum CH1 + CH2, displayed with the VOLTS/DIV and POSITION settings of CH1; X-Y: CH1 deflects horizontally (X), CH2 vertically (Y).

In X-Y mode the horizontal POSITION ↔ shifts the X deflection, and A TIME/DIV sets how long a section of the signals is drawn (ten times its value) — choose it so that at least one full period of the slower signal is drawn. The trigger is not used in X-Y mode.

Horizontal system (time base)

A TIME/DIV
Main time base (time coefficient), 1 µs/div to 0.5 s/div in 1-2-5 steps; dark blue values are milliseconds, light blue ones microseconds. Clockwise is faster. At 20 ms/div and slower the beam is seen travelling across the screen in real time.
B TIME/DIV
Delayed time base. It cannot be set slower than A; the knob stops at the A setting.
DELAY
Delay time position: the B sweep starts this many A divisions (0–10) after the start of the A sweep. While turning, the label shows the delay in time as well.
POSITION ↔
Horizontal shift, ±5 divisions. Moving the trace to the right also reveals part of the signal before the trigger point. (A real analog oscilloscope shows only a few nanoseconds there, thanks to its delay line; the simulation can show more.)
DISPLAY
A: main sweep. A INT: main sweep with the section that B will show intensified (the rest is dimmed). B: only the delayed sweep, i.e. the intensified section expanded to the full screen.
×10 (MAGNIFIER)
Expands the centre division horizontally ten times; the effective time coefficient is the TIME/DIV setting divided by 10. Works with A, A INT and B.

Trigger

The trigger starts each sweep at the same point of the signal, so that successive sweeps lie on top of each other and the picture stands still. The trigger point is the left edge of the screen (with POSITION ↔ at zero).

LEVEL
Trigger level, ±4 divisions on the scale of the source channel (for EXT 0.5 V per scale unit, i.e. ±2 V). Not used with LINE.
SOURCE
CH1, CH2, EXT (the external trigger input) or LINE. On a real instrument LINE synchronizes to the 50/60 Hz mains, to observe mains-related signals such as hum; here it is an internal 50 Hz reference, mainly for completeness.
SLOPE
+ ↑: trigger on the rising edge, − ↓: on the falling edge.
MODE
AUTO: without a valid trigger the sweep free-runs, so a trace (baseline) is always visible — best for unknown signals. NORM: a sweep runs only when a trigger occurs; without trigger the screen stays dark. SINGLE: single sweep — see below.
SINGLE RESET, READY
In SINGLE mode RESET arms the sweep and the READY lamp lights. Only a trigger that comes after arming starts the sweep; after one sweep the time base is locked out and READY goes out, until RESET is pressed again.
EXT TRIG IN
Source of the external trigger signal: GEN 1, GEN 2 or AUDIO (mono mix of the audio input).
TRIG'D
Lights while the sweep is being triggered.

Difference from a real instrument: on an ordinary cathode-ray tube a single sweep flashes up once and fades with the phosphor, so it had to be photographed. The OSC-2 keeps the captured sweep on the screen, as a storage oscilloscope would; turning the knobs does not erase it, only SINGLE RESET or a change of mode does.

FG-2 function generator

Two independent outputs, OUT 1 and OUT 2. Their signals reach the oscilloscope through the INPUT, Z INPUT and EXT TRIG IN switches; the OUTPUT connectors are only a symbol of that connection.

WAVEFORM
Sine, square, pulse (duty cycle 20 %, unipolar from 0 V to the set amplitude), triangle, sawtooth, noise (band-limited to about 20 × the set frequency).
FREQUENCY
0.5 Hz to 100 kHz, logarithmic scale.
AMPLITUDE
0–10 V peak-to-peak (Vpp).
OFFSET
DC offset, −5 V to +5 V.
PHASE
0–360°. Both outputs share the same time origin, so at equal frequencies the phase difference of the two outputs is the difference of the two PHASE settings.
AUDIO (LEFT/RIGHT)
Also sends OUT 1 to the left and OUT 2 to the right loudspeaker or headphone channel. The DC offset is not reproduced.
VOLUME
Loudness of the audio output only; it does not change the signal seen on the oscilloscope. At 100 %, 10 Vpp corresponds to digital full scale; louder signals are clipped.

The red display shows waveform, frequency, amplitude and offset of both outputs; ♪ marks an output that is also sent to the sound card. Sound cards reproduce roughly 20 Hz to 20 kHz: above half the sampling rate (22 or 24 kHz) the audio output is distorted by aliasing, although the oscilloscope still shows the ideal signal.

Live audio inputs

  • AUDIO IN uses the microphone or line input. With a stereo input the left channel goes to CH1 and the right channel to CH2.
  • AUDIO OUT shows the sound the computer is playing. The browser asks which tab or screen to share — tick Share audio. Works in desktop Chrome and Edge, not on phones.
  • Digital full scale corresponds to ±1 V. Sound cards are AC-coupled and band-limited (about 20 Hz–20 kHz), so DC and AC coupling look the same here.
  • The browser asks for permission the first time; live audio needs a secure (https) page. In embedded views — for example the preview inside Claude — microphone and screen sharing are blocked: the affected positions are crossed out. Open the page on its own site (e.g. on Vercel) to use them.
  • The oscilloscope keeps about 11 seconds of audio history; the picture follows the sound with the small latency of the sound card.

Presets and readings

Presets set up a complete measurement: Default, Lissajous 3:2, Beats, Noisy signal, AC coupling, Z modulation, Delayed sweep, Slow sweep. They reset the inputs to the generator but keep the audio-output settings.

The readings cards are calculated from the section currently on the screen (in B mode or with ×10, the expanded section): Vpp peak-to-peak value, Vrms (AC) RMS value of the AC component, Mean mean (DC) value, Frequency (needs more than one full period on the screen). In X-Y mode a card shows the frequency ratio fx : fy and the phase difference of the generators.

Differences from a real analog oscilloscope

  • Unlimited bandwidth: the OSC-2 has no rise time of its own and no bandwidth limit. Real signals taken from the sound card are, however, limited by the sound card.
  • DUAL draws both channels at once; real instruments alternate (ALT) or chop (CHOP) between them.
  • No variable (uncalibrated) VOLTS/DIV, no trigger holdoff, no trace rotation, no probe compensation.
  • AC coupling is ideal (no low-frequency cut-off), LINE uses an internal 50 Hz reference, and a single sweep is stored on the screen.

Terminology in four languages

EnglishDeutschРусскийMagyar
deflection coefficient (VOLTS/DIV)Ablenkkoeffizientкоэффициент отклоненияeltérítési tényező
time coefficient, time base (TIME/DIV)Zeitkoeffizient, Zeitbasisкоэффициент развёртки, развёрткаidőalap (idő/osztás)
division (div)Teil (Div)деление (дел)osztás
graticuleRasterмасштабная сеткаosztásháló
input coupling: DC / AC / GNDEingangskopplung: DC / AC / GNDоткрытый / закрытый вход / вход заземлёнcsatolás: DC / AC / GND (földelt)
dual-trace modeZweikanalbetriebдвухканальный режимkétcsatornás üzemmód
algebraic addition (ADD)Additionsbetriebалгебраическое сложениеalgebrai összegzés
X-Y modeXY-Betriebрежим X-YX-Y üzemmód
triggeringTriggerungсинхронизация (запуск развёртки)indítás (triggerelés)
trigger levelTriggerpegelуровень синхронизацииindítási szint
slope: rising / falling edgeTriggerflanke: steigend / fallendполярность: по нарастанию / по спадуél: felfutó / lefutó
trigger sourceTriggerquelleисточник синхронизацииaz indítójel forrása
external triggerexterne Triggerungвнешняя синхронизацияkülső indítás
line triggerNetztriggerungсинхронизация от сетиhálózati indítás
auto modeautomatische Triggerungавтоколебательный режимautomatikusan indított üzemmód
normal modeNormaltriggerungждущий режимnormál (indított) üzemmód
single sweepEinzelablenkungоднократный режим (однократная развёртка)egyszeri eltérítés
delayed sweep (B)verzögerte Zeitbasis (B)задержанная развёртка (Б)késleltetett eltérítés (B)
A intensified by B (A INT)A hellgetastet durch BА с подсветом участка БA kiemelt B-szakasszal
delay time positionVerzögerungszeitвремя задержкиkésleltetési idő
×10 magnifierX-Dehnung ×10растяжка ×10×10-es nyújtás
Z-axis input, intensity modulationZ-Eingang, Helligkeitsmodulationвход Z, модуляция яркостиZ-bemenet, fényerő-moduláció
intensity, focusHelligkeit, Schärfeяркость, фокусировкаfényerő, fókusz
persistenceNachleuchtdauerпослесвечениеutánvilágítás
rise time (10–90 %)Anstiegszeit (10–90 %)время нарастания (0,1–0,9)felfutási idő (10–90 %)
phase differencePhasendifferenzсдвиг фазfáziskülönbség
Lissajous figureLissajous-Figurфигура ЛиссажуLissajous-ábra
beatSchwebungбиенияlebegés
function generatorFunktionsgeneratorфункциональный генераторfüggvénygenerátor
peak-to-peak value (Vpp)Spitze-Spitze-Wert (Vss)размахcsúcstól csúcsig érték (Vpp)
RMS valueEffektivwertсреднеквадратичное значениеeffektív érték
DC offsetGleichspannungsoffsetпостоянное смещениеegyenfeszültségű eltolás (ofszet)
duty cycleTastverhältnisкоэффициент заполненияkitöltési tényező

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