The symbol for potentiometer depends entirely on your regional drafting standard: the US-based IEEE/ANSI standard uses a zigzag resistor line with an arrow pointing to the center, while the international IEC standard uses a rectangular box with an arrow. Regardless of the schematic symbol, the physical pinout remains universal across almost all 3-terminal variable resistors: Pin 1 is the counter-clockwise (CCW) end, Pin 2 is the wiper, and Pin 3 is the clockwise (CW) end.
Below is the complete reference data you need to read, draw, and wire these components correctly, followed by a decision framework for selecting the exact physical part for your next build.
Potentiometer Symbol and Pinout Reference Table
Use this table to cross-reference schematic symbols with physical wiring. This covers the standard 3-terminal pot, the 2-terminal rheostat configuration, and the trimpot (preset) variant.
| Component / Config | IEEE/ANSI Symbol (US) | IEC 60617 Symbol (Global) | Physical Pinout (1-2-3) | Primary Use Case |
|---|---|---|---|---|
| Standard Potentiometer | Zigzag line, arrow from center | Rectangle, arrow from center | 1: CCW, 2: Wiper, 3: CW | Voltage divider, user input |
| Rheostat (Variable Resistor) | Zigzag line, arrow to one end, 2 terminals shown | Rectangle, arrow to one end, 2 terminals shown | 1 & 2 tied (or 2 & 3 tied) | Current limiting, analog dimming |
| Trimpot (Preset) | Zigzag line, arrow with a T-bar or box | Rectangle, arrow with a T-bar or box | 1: CCW, 2: Wiper, 3: CW | One-time calibration, bias setting |
| Ganged Pot (Dual) | Two parallel pot symbols, dashed line linking wipers | Two parallel rectangles, dashed line linking wipers | Two independent 1-2-3 sets on one shaft | Stereo audio volume control |
Regional Standards: IEEE 315 vs. IEC 60617
Understanding which symbol applies to your region prevents schematic misinterpretation, especially when ordering parts or collaborating across borders.
IEEE/ANSI Y32.2 (North America): Governed by the standard resistor symbols familiar to US engineers, the potentiometer is drawn as a zigzag line. The zigzag represents the resistive carbon or cermet track, and the arrow represents the wiper. This standard is dominant in US universities, legacy military schematics, and North American hobbyist circles.
IEC 60617 (Europe, UK, Asia, Global): The International Electrotechnical Commission replaced the zigzag with a simple rectangular box to represent all fixed and variable resistors. The potentiometer is a rectangle with an arrow touching the side. If you are reading modern European equipment manuals (like Behringer audio gear or Siemens industrial panels), you will exclusively see the IEC box symbol.
The Grounded Terminal Convention: In both standards, if the potentiometer is used strictly as a voltage divider (e.g., a volume knob), the schematic will typically show Pin 1 (CCW) tied to circuit ground, Pin 3 (CW) receiving the input signal, and Pin 2 (Wiper) outputting the divided voltage. However, always verify this against the specific circuit's signal flow, as reverse-wiring a linear pot works fine electrically but reverses the mechanical user experience.
Rows and Markings People Get Wrong
The schematic symbol only tells half the story. The physical silkscreen markings on the potentiometer casing dictate its electrical behavior, and misinterpreting these is a primary cause of prototype failure.
The Taper Code Trap (A vs. B vs. C)
The most critical marking on a pot is the taper code, usually stamped right after the resistance value (e.g., 10kΩ B). Here is where builders get burned:
- B Taper (Linear): The resistance changes at a constant rate relative to shaft rotation. 50% rotation = 50% resistance. Used for voltage dividers, sensor scaling, and synthesizer LFO rate controls.
- A Taper (Logarithmic / Audio): The resistance changes exponentially. This matches human hearing perception, making it mandatory for audio volume controls. 50% rotation might only yield 10% of the total resistance.
- The Regional Flip: In modern US and Asian manufacturing, A = Log and B = Linear. However, in vintage European equipment (and some modern European replacements), the codes are flipped: A = Linear and B = Log. Always verify the taper with a multimeter if working on vintage Euro gear.
Trimpot Orientation (Top-Adjust vs. Side-Adjust)
When reading a Bill of Materials (BOM) for a PCB layout, the symbol for potentiometer won't tell you the physical orientation. A Bourns 3296W is top-adjust (screw on top), while a 3296Y is side-adjust. Ordering the wrong variant means your tuning screwdriver won't reach the adjustment slot once the enclosure is closed.
Safe Interpretation When Markings Are Faded or Missing
On salvaged boards or heavily used audio equipment, the silkscreen taper codes and pin numbers are often rubbed off. Do not guess the wiring. Use this 3-step digital multimeter (DMM) procedure to safely map the pins and determine the taper.
- Identify the Total Resistance (End Pins): Set your DMM to the appropriate Ohms range (e.g., 20kΩ). Probe the outer two pins. The reading should match the nominal value (e.g., ~10,000Ω for a 10k pot) within a ±20% tolerance. The middle pin is your wiper.
- Identify the Wiper and Direction: Place one probe on the identified wiper and the other on one of the outer pins. Turn the shaft. If the resistance increases as you turn clockwise, the pin under your stationary probe is Pin 1 (CCW). If it decreases, it's Pin 3 (CW).
- Determine the Taper (Linear vs. Log): Set the shaft to the exact mechanical center (50% rotation). Measure the resistance between the wiper and Pin 1.
- If the reading is approximately 50% of the total resistance (e.g., ~5kΩ on a 10k pot), it is a Linear (B) taper.
- If the reading is roughly 10% to 15% of the total resistance (e.g., ~1kΩ to 1.5kΩ on a 10k pot), it is a Logarithmic/Audio (A) taper.
Decision Path: Selecting the Right Potentiometer for Your Circuit
Use this decision tree to terminate your design phase with a concrete, purchasable part number. The Bourns 3296 datasheet and Alps catalog remain the industry benchmarks for these selections.
| Application Scenario | Required Specs | Concrete Part Recommendation |
|---|---|---|
| PCB Calibration / Bias Setting (e.g., setting op-amp offset, trimming LED current) |
Multi-turn for precision, cermet track for thermal stability (up to 125°C), through-hole. | Bourns 3296W-1-103LF (10kΩ, 25-turn, top-adjust cermet trimpot) |
| Audio Volume Control (e.g., guitar pedal, preamp, mixer channel) |
Audio (Log) taper, carbon track for low wiper noise, dual-ganged for stereo. | Alps Electric RK27 10kA (Dual-gang 10kΩ Audio taper, 9mm shaft) |
| Microcontroller Analog Input (e.g., ESP32 ADC dimmer dial, Arduino sensor threshold) |
Linear taper, single turn, panel mount, low cost. | TT Electronics P231-FC20BR10K (10kΩ Linear, single-turn, PCB mount) |
| High-Power Motor Speed Control (e.g., analog DC motor throttle, 12V/24V systems) |
Wirewound track (handles >0.5W), high current rating, rheostat wiring. | Vishay 534B1103JC (10kΩ Wirewound, 2W power rating) |
By matching the correct schematic symbol to your regional standard and verifying the physical taper and pinout before soldering, you eliminate the most common points of failure in analog control circuits. When in doubt, default to a linear (B) cermet trimpot for prototyping; it is the most forgiving and universally useful component on the bench.
