POLYSHINEHK / TECHNICAL GUIDE
Rotary potentiometers: a practical technical guide
A rotary potentiometer is a three-terminal variable resistor adjusted by turning a shaft. This guide explains how the parts of a rotary potentiometer work together, which parameters matter when specifying one, and the exact values we manufacture on our 9 mm F09K series.
How a rotary potentiometer works
Two outer terminals connect the ends of a resistive track; the centre terminal connects to a wiper that slides along that track as the shaft rotates. Wired across the full track it works as a voltage divider; wired to one end and the wiper it works as a simple variable resistor.
The resistive track can be carbon film (cost-effective, the usual choice for audio and general control) or conductive plastic. The relationship between shaft angle and output is the taper: B is linear, A and C are logarithmic curves used where human perception is non-linear, such as volume control.
Rotary potentiometers are continuous analogue devices, unlike rotary encoders, which output digital pulses. If you need absolute position sensing with a simple ADC input, a potentiometer is normally the simpler and cheaper answer.
What to specify
- Total resistance and tolerance
- Pick the resistance from the standard range, then check the tolerance band, which widens at the extremes of the range.
- Taper (A, B or C)
- Linear for measurement and set-point control, logarithmic for audio level and anything judged by ear.
- Gang number
- A single gang for mono or single-axis control, dual gang for stereo channels or two tracks driven by one shaft. Rated power and detent availability differ between them.
- Terminal style and mounting
- Top adjust or side adjust, with or without a sleeve bushing. This decides how the part sits relative to the board and the panel.
- Shaft type and length
- Splined, slotted, knurled and flatted shafts each suit different knobs. Shaft length also constrains whether a bushing can be fitted.
- Detents and rotational life
- A centre detent or 21-step detent gives tactile feedback; a long-life build is available where the control is turned frequently.
Typical applications
- Audio volume, tone, balance and gain controls in amplifiers, mixers, guitar pedals and instrument panels
- Set-point and trim adjustment on industrial controllers, power supplies and test equipment
- Speed, brightness and temperature dials on appliances and professional equipment
- Position and angle reference for joysticks, robotics and motion control assemblies
- Front-panel user controls on medical, laboratory and automotive interior modules
General specifications — F09K series
Values below are the published specifications for our 9 mm square insulated shaft rotary potentiometer. Other sizes and custom builds are quoted case by case.
- Total resistance
- 1KΩ ~ 1MΩ
- Total resistance tolerance
- 500Ω < R < 1MΩ: ±20%; R ≤ 500Ω or R ≥ 1MΩ: ±30%
- Resistance taper
- A, B, C
- Max. operating voltage
- AC 50V / DC 20V
- Rated power
- Single unit: 0.05W; Dual unit: 0.03W
- Rotational noise
- Less than 100mV
- Insulation resistance
- More than 100MΩ at DC 250V
- Withstand voltage
- 1 minute at AC 250V
- Residual resistance
- Term. 1~2: less than 20Ω; Term. 2~3: less than 20Ω
- Gang error (dual unit)
- −40dB ~ 0dB ± 3dB
- Gang number
- Single gang (N) / Dual gang (G)
- Detent option
- No detent / center detent (single gang) / 21 detents (single gang)
- Total rotational angle
- 280° ± 10°
- Rotational torque
- 10 ~ 90 gf·cm
- Stopper strength
- 3.0 Kgf·cm Min.
- Push-pull strength
- 5.0 Kgf Min.
- Click torque
- 30 ~ 120 gf·cm
- Rotational life
- Standard: 15,000 cycles Min.; Long life: 100,000 cycles Min.
- Operating temperature range
- −10°C ~ +70°C
Dimensions and construction
- Body size
- 9 mm square
- Terminal & bushing
- H top adjust bushingless / V side adjust bushingless / A top adjust with sleeve bushing / B side adjust with sleeve bushing
- Height (H)
- 0 = N/A (top adjust only), 1 = 6.5 mm, 2 = 10.0 mm, 3 = 12.5 mm (side adjust only)
- Shaft type
- F / N / C / Y / T / D / P / Q / K types (splined, slotted, knurled and more)
- Shaft length
- Specified by code; bushing available only when shaft length exceeds 20 mm
- Full CCW position
- C / A / D group per shaft type, 40° ± 10°
Build the exact part number
The F09K page includes a part-number builder that only allows valid option combinations, so the code you send us is one we can manufacture.