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Design Note
Potentiometer Taper
Defining the relationship between the mechanical position and its resistance ratio
Potentiometer taper is a fundamental concept in electronic component design, defining the relationship between the mechanical position of the potentiometer and its resistance ratio.
For the majority of variable resistors on the market, this relationship is linear—meaning the relative position directly equals the percentage of the resistance ratio. For example, when a linear pot is set to its middle position, the output voltage is exactly half of the full voltage. However, many specialized applications—particularly audio volume control—require non-linear, logarithmic tapers.
Understanding Different Types of Taper
When we plot a potentiometer’s physical position against its resistance ratio, we can visualize the different position-resistance relationships. It’s important to note that the first and last few percent of a potentiometer’s travel are often purely mechanical, causing no change in resistance. The active region (typically between 5% and 95%) is known as the electrical travel.
Linear Taper (Taper B)
The most common type of variable resistor uses a linear taper. In these components, the change in resistance is directly proportional to the rotation of the shaft. They are ideal for applications where a straightforward, proportional control of voltage or current is necessary.
Audio Taper / Logarithmic Taper (Taper A)
The most widely used non-linear profile is the audio taper (also known as a logarithmic or log taper). Its primary application is in audio volume control, designed specifically to provide a more natural, “linear” perception of sound intensity as you adjust the dial.
Because the human ear processes sound intensity logarithmically, a small change in actual intensity at low volumes is perceived as a significant change in loudness. Conversely, at high volumes, a much larger change is required to perceive the same difference. Audio taper potentiometers feature an exponential curve (the inverse of human hearing) to perfectly compensate for this biological behavior.
Reverse Logarithmic Taper (Taper C)
In certain specialized applications, a reverse logarithmic taper is required. These are most commonly utilized in audio controls that are designed to turn counterclockwise, or in specific analog circuits requiring inverse exponential resistance curves.
Dual Tapers with Center Detent (Taper M/N)
Some advanced applications call for a dual taper design featuring a center detent:
- M Taper: Delivers 0% to 100% output voltage from 0% to 50% rotation (linear), and holds 100% output voltage from 50% to 100% rotation.
- N Taper: The exact opposite. It holds 100% output voltage from 0% to 50% rotation, and scales linearly from 100% down to 0% output voltage between 50% and 100% rotation.
Both the M and N tapers hit their full output exactly at the 50% rotation mark (the center detent).
Source Custom Potentiometers with ISL Products
While many standard variable resistors are available off-the-shelf, specialized applications demand exact specifications. At ISL Products, we offer a wide variety of taper profiles, with a heavy specialization in custom potentiometers and audio tapers.
Over the years, we have manufactured potentiometers featuring over a dozen different types of audio tapers. Furthermore, if your component is destined for an abnormal or harsh environment, our engineering team can design a robust solution tailored to your operational conditions.Don’t settle for “off-the-shelf” limitations. Submit your requirements today to get a detailed specification sheet and quote for your next project.
