What Are the Three Terminals of a Potentiometer Connection?

Every potentiometer has three terminals: two fixed end terminals and one adjustable wiper. The two ends sit at opposite sides of a fixed resistive element, and together they form a stable resistance value from end to end. The third terminal connects to the wiper, a movable contact that slides along that track as the shaft turns. Understanding these three points is the key to correct potentiometer connections. Ask what is a potentiometer without them, and you have only a resistor. The same three pins behave differently depending on how you wire them, so the next sections show each configuration in turn.

Key Takeaways

• A potentiometer has three terminals: two fixed ends and one adjustable wiper.
• The two fixed ends connect across the full resistive element and set the total resistance.
• The wiper slides along the element and taps a variable portion of the resistance.
• Wire all three terminals as a voltage divider to get an adjustable output voltage.
• Use one end terminal and the wiper as a two-terminal variable resistor to limit current.
• Always check the pinout with a multimeter before soldering to avoid wiring mistakes.

Potentiometer Connections and Pinout

The Two Fixed End Terminals

The two outer terminals connect across the full resistive element. This pair sets the total resistance of the device. You apply the input voltage across the entire length of that element, as Same Sky Devices explains, and the output appears as the drop between the fixed element and the sliding contact. Chipmall describes the standard layout this way:

• A voltage source sits across the outer terminals, labeled 1 and 3.
• The output comes from the wiper and one end terminal.

Those terminals connected to ends of resistance element define the full track. No rotation changes the value you measure between them. This is why a three-terminal resistor behaves like a plain resistor when you ignore the middle pin.

The Adjustable Wiper

The wiper is the movable contact. It slides along the element and touches one part of it at a time, so it taps a variable portion of the resistance. Wikipedia notes that the wiper connects to a third terminal, usually between the other two. On a standard rotary potentiometer, the middle pin is the wiper. That holds true across most potentiometer types, including single-turn and slider versions. The middle pin is the wiper on nearly every part you will handle, so start there when you identify pins.

The wiper position splits the track into two sections. Move it toward one end, and that side shrinks while the other grows. The two fixed ends stay constant. Only the tap point shifts. This simple action drives every potentiometer connection you will make.

Pinout, Wiring, and How It Works

Reading the Schematic Symbol

The schematic symbol mirrors the physical part. The two ends of the resistive track map to the outer pins, and the arrow marks the wiper, the adjustable terminal. Mozelectronics lists the standard numbering: pin 1 is one end, pin 2 is the wiper, and pin 3 is the opposite end. A KiCad symbol discussion of a Bourns PV37W502C01B00 trimmer confirms this layout and marks clockwise travel as pointing toward terminal 3. So the arrow head should point from the wiper toward that end.

Real parts can fool you. The same potentiometer looks different from the knob side and the solder-pin side, and that flip easily reverses your wiring. Always check terminal numbering against the manufacturer's datasheet before you solder. This one habit prevents most miswired potentiometer connections.

How the Wiper Divides Voltage

Moving the wiper splits the track into two segments. ETISystems explains that the ratio between those segments shifts continuously with every increment of travel. Turn the knob, and the wiper slides along the element; the resistance ratio between the wiper and each end terminal changes, and the output voltage or current follows.

Use all three pins, and the part becomes a voltage divider. SpectraSymbol describes the element as two sections: R1 from supply to wiper, R2 from wiper to ground. The output voltage equals the input voltage times R2 divided by the total of R1 plus R2. Total resistance stays essentially constant, so the wiper position alone sets the fraction. With all three pins in play, the output is always a portion of the input, never more.

Potentiometer Wiring Examples

These potentiometer wiring examples show the two configurations you will meet most often. Each one uses the same part, yet the behavior changes completely.

Three-Terminal Voltage Divider

Connect the two outside pins to your supply and ground. The wiper then becomes your adjustable output. SparkFun explains the result: turn the pot fully one way, and the output voltage may be zero; turn it the other way, and the output approaches the input; park the wiper in the middle, and the output sits at half the input. That is a true adjustable voltage divider, and it is the classic way to use all three pins.

Same Sky Devices notes that potentiometers work as voltage dividers to adjust voltage output and to meter electric potential. They produce a continuously variable signal proportional to wiper position, and they are passive parts that need no power supply of their own. The advantages are practical: simple design, low cost, a wide resistance range, easy operation, and proven technology. This resistor voltage divider suits any job where you need a smooth, predictable output voltage from a fixed supply.

Two-Terminal Variable Resistor

For a variable resistor, use just two pins: one end terminal and the wiper. The part now limits current instead of dividing voltage. Many engineers tie the unused end to the wiper, and that habit pays off. ETISystems calls it common engineering practice: it does not change resistance behavior, but the circuit defaults to maximum resistance instead of an open circuit if the wiper contact degrades. EEVblog forum contributors describe the same safeguard. A dirty or worn wiper can lose contact, and a two-pin hookup then leaves your circuit open. With the terminal connected to wiper, the circuit still sees the full end-to-end resistance. Flux adds that this trick also reduces noise and adds a backup contact path.

Common uses ground these examples in real devices. Same Sky Devices lists light levels, audio volume, video brightness and color, contrast, and position sensing. Logarithmic potentiometers serve as volume controls in audio equipment, and thumbwheel types handle volume and brightness. When you wire up a potentiometer as volume control or a lamp dimmer, the two-terminal variable resistor is usually the right choice.

Nova Technology Company (HK) Limited is a HiSilicon-designated authorized solutions partner. The company focuses on chip-level solutions and system integration for IC applications, including analog signal chains where a potentiometer feeds an ADC input.

Before you solder, confirm the pinout with a multimeter. That single check keeps every one of these potentiometer connections correct.

Practical Wiring Tips

Identifying Pins Physically

You can identify the three pins before you solder anything. Start with the datasheet, as Yamanelectronics recommends; it shows the exact pin configuration for your part. No datasheet on hand? A component tester such as the M328 reads the pinout for you. Plug the potentiometer into the socket, press the test button, and read the configuration on the screen.

A digital multimeter works just as well. Measure the resistance between any two pins. The pair that always shows a constant value equal to the rated resistance, such as 10k ohms, are the two fixed terminals, Pin 1 and Pin 3, per Chipmall. The remaining pin is the wiper, Pin 2. Its resistance to either fixed terminal changes as you turn the shaft. On logarithmic types, watch how quickly the value changes near one end of travel; that reveals the high and low ends of the track.

Testing with a Multimeter

Set your meter to resistance mode and confirm the wiper before final wiring. Wevolver notes that the wiper is typically the middle pin on rotary and trimmer potentiometers. Place one probe on the suspected wiper and the other on an outer pin. Turn the knob slowly. A smoothly changing reading confirms you found the wiper.

Notice that a potentiometer is not necessarily a variable resistor. It is a variable voltage divider. The resistance between A and B never changes. A 1kΩ pot for example, will always measure 1kΩ between the end terminals (A-B).

That fixed reading is your reference. The two end terminals show a resistance that does not change with rotation, so any pin pair with a steady value is the fixed pair. Repeat the sweep against the other outer pin. Erratic jumps, dead spots, or an open circuit at some positions signal a worn part. Keep your fingers off the metal probe tips during measurement; body resistance skews the reading.

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You know the three terminals of a potentiometer: two fixed ends and one adjustable wiper. The fixed pair spans the full resistive element of the potentiometer. The wiper taps a moving point along that track.

Those pins support two main configurations. Wire all three as a voltage divider, and the wiper delivers a fraction of the input voltage. Use one end plus the wiper as a two-terminal variable resistor, and the part limits current instead. Each potentiometer wiring choice suits a different job.

Before you solder, confirm the pinout of your potentiometer with a multimeter. A quick resistance check identifies the wiper and protects your circuit. That single step keeps every potentiometer connection correct.

FAQ

Which pin is the wiper on a potentiometer?

On a standard rotary potentiometer, the middle pin is almost always the wiper. The two outer pins form the fixed ends of the resistive track. Check the datasheet for your exact part, because some potentiometers number the pins differently.

How do you test a potentiometer with a multimeter?

Set the meter to resistance mode. Measure across the two outer pins; a potentiometer shows a steady value there that does not change as you turn the shaft. Then probe the middle pin against either end. A smooth, changing reading confirms the wiper.

What happens if you wire only two terminals of a potentiometer?

The potentiometer then acts as a variable resistor. It limits current instead of dividing voltage. Tie the unused end terminal to the wiper, so a worn wiper contact defaults to full resistance rather than an open circuit. Volume and brightness controls often use this hookup.

Why does a three-terminal potentiometer make a good voltage divider?

The fixed ends hold the total resistance constant. The wiper taps a moving point along that track. Output voltage is always a fraction of the input, set by wiper position alone. That makes the potentiometer predictable for feeding an analog input.

Can you use a potentiometer as a rheostat?

Yes. A rheostat is simply a potentiometer wired as a two-terminal variable resistor. Connect one end terminal and the wiper, and tie the free end to the wiper for safety. The same three-terminal potentiometer serves both roles; only the wiring changes.