Source: https://fullstackelectronics.com/reference/function-generator

# The Function Generator

The four things any generator must do for this course, and the exact keystrokes to do them on the reference instrument.

Any function generator will serve this course, provided it can do four things: produce a **ramp or triangle waveform**, set the exact **high and low voltage levels** the circuit will see, set the **frequency**, and be told it is driving a **high-impedance load** rather than 50 Ω. The keystrokes below are for the course's reference instrument, the Siglent SDG1062X; read them for their intent and translate to whatever is on your bench.

## Know your instrument

- **Two channels, 60 MHz maximum**, 14-bit. The 4.3″ screen is **not a touchscreen**: everything happens through the softkeys under the screen, the numeric keypad, the knob, and the arrow keys.
- Two Output keys sit on the right of the front panel, one per channel. A lit backlight means a signal is flowing.
- Output range: up to ±10 V into a high-impedance load (±5 V into 50 Ω).

## The start-of-session ritual

Run these five steps, in order, every time you sit down. Keep this page open for the first few bench sessions.

1.  **Set the load to HiZ first.** Utility → Output Setup → Load → select **HiZ**. Shortcut: **hold the channel's Output key for about two seconds** to toggle between 50 Ω and HiZ. The generator's output impedance is always physically 50 Ω; this setting only tells the readout maths what load to assume. Left at "50 Ω" while driving a breadboard, every voltage on screen arrives *doubled* at the circuit.
2.  **Pick the waveform.** Waveforms → Ramp. There is no "Triangle" button: a **triangle is a Ramp at Symmetry 50%** (50% is the power-on default; check it under Symmetry; 100% would give a sawtooth). A slow triangle is an even sweep of every input voltage, which is exactly what you want for hunting a threshold.
3.  **Set the frequency.** Press Frequency, type the value on the keypad, and finish with the unit softkey (e.g. Hz). Pressing Frequency again toggles to Period entry; the active mode shows in inverse colour.
4.  **Set the levels the circuit-thinking way.** Press Amplitude *twice* and it switches to **HighLevel** (shown in inverse colour); press Offset *twice* and it becomes **LowLevel**. Now you enter what the circuit actually sees (low 0 V, high 2 V) instead of converting to "2 Vpp with a 1 V offset" in your head. This is the difference between dialling a clean **0–5 V** logic swing in two presses and getting it subtly wrong by setting amplitude alone.
5.  **Connect, then enable.** Cables on first, then press Output for the channel. The backlight lights and the signal flows. Press it again to kill the output.

**If the circuit sees twice what you dialled in:** the load setting has fallen back to 50 Ω. Hold the channel's Output key for two seconds to flip it to HiZ. This is probably the most common gotcha with this generator, and some level-entry operations quietly reset it, so check it at the start of every session, and again after any level entry.

## Read back before you trust the breadboard

When a measurement looks wrong, the generator is as likely a suspect as the circuit. Before you start probing the breadboard, glance at the channel summary on the generator's screen and confirm all four things at once:

- **Load** reads **HiZ** rather than 50 Ω.
- **HighLevel** and **LowLevel** are the numbers you meant (not an amplitude/offset pair you have to convert).
- The **frequency** is right, and it is Frequency rather than Period that is showing.
- The Output backlight is **lit**; a dark key means no signal is leaving the box.

Two seconds of read-back saves ten minutes of chasing a "dead" circuit that was never being driven.

## Standard hookup

One generator output feeds two places: the scope, so it sees the true input, and the circuit. Split it with a BNC T:

| Path | Hardware |
|----|----|
| Generator → scope CH1 | SDG1062X CH1 → BNC cable → **T adapter on scope CH1** (the scope monitors the true input) |
| Generator → circuit | The T's free port → BNC-to-mini-hook lead: red hook = circuit IN, black hook = breadboard GND |
| Circuit → scope CH2 | A scope probe: its hook on the node under test, its ground clip on breadboard GND |
| Grounds | Every black hook and clip to the same ground rail. The generator and scope grounds are both referenced to mains earth; they are already connected to each other behind your back. |

The T-split is sound practice at these frequencies: the scope's 1 MΩ input barely loads the line, so both destinations see the same waveform. And when a trace looks like garbage, suspect a forgotten ground first.

## A worked example: the first sweep (Experiment 3)

The settings that drive the almost-comparator in [Experiment 3](https://fullstackelectronics.com/experiments/03-the-almost-comparator.html.md); copy them exactly the first time, then you will know the moves:

| Setting | Value | How |
|----|----|----|
| Load | HiZ | Hold Output 2 s (or Utility → Output Setup → Load) |
| Waveform | Ramp, Symmetry 50% | Waveforms → Ramp |
| Frequency | 100 Hz | Frequency → 1 0 0 → Hz |
| LowLevel | 0 V | Offset ×2 → 0 → V |
| HighLevel | 2 V | Amplitude ×2 → 2 → V |
| Output | CH1 on | Output (CH1); backlight lit |

## Good to know later

- **You have a second channel.** From [Experiment 4](https://fullstackelectronics.com/experiments/04-the-differential-pair.html.md) onward you can drive a comparator's reference input from CH2 (a fixed DC level) while CH1 sweeps the other input.
- Frequency entry defaults to 1 kHz on power-up, and every setting is stored per channel.

**Sources (verified):** [SDG1000X User Manual (PDF)](https://siglentna.com/wp-content/uploads/dlm_uploads/2024/08/SDG1000X_UserManual_UM0201X-E01H.pdf) · [Quick Start Guide (PDF)](https://siglentna.com/wp-content/uploads/dlm_uploads/2017/10/SDG1000X_QuickStart_QS0201X-E01B.pdf) · [product page](https://siglentna.com/product/sdg1062x/) · video: ["How it Works: SIGLENT SDG1000X Series"](https://www.youtube.com/watch?v=Juf995ZAjqg). Keystrokes verified against Siglent's user manual UM0201X-E01H.