> For the complete documentation index, see [llms.txt](https://docs.sevenpens.com/drawtab/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.sevenpens.com/drawtab/core/pressure.md).

# Pressure

## Overview

**Pressure** is the physical force exerted on the pen tip. The pen and tablet translate that physical pressure into a logical number sent to the tablet (that is, the pressure level).

## Key concepts

* **The pen senses pressure**, not the tablet. The pen communicates the pressure it detects to the tablet.
* **Physical Logical** - The tablet and pen work with two systems for describing pressure
  * physical pressure - the actual force a tthe tip of the pen in an absolute unit like gram-force (gf).
  * logical pressure - an abstract number representing the relative amount of pressure that does not have a unit. This could be considered to be a number between 0.0 and 1.0 or equivalently a number between 0% and 100% or even a pressure level number.
* The [pressure range](broken://pages/SpXfHs0XHkS6Dnt4279C) is the range of physical force the pen can sense.
  * The lower bound is the [Initial Activation Force (IAF)](/drawtab/core/pressure/iaf.md).
  * The upper bound is the [maximum physical pressure](/drawtab/core/pressure/maximum-physical-pressure.md).
* A tablet splits the pressure range into logical segments called [Pen pressure levels](/drawtab/core/pressure/pen-pressure-levels.md).
* The [Pen's pressure response](/drawtab/core/pressure/pen-pressure-response.md) is the pen hardware's pressure behavior. It describes how a specific pen maps physical pressure to the logical pressure number sent to your computer.
* A [pressure curve](/drawtab/core/pressure/pressure-curves.md) processes the pressure response of a pen. You can use it to solve or mitigate some pressure problems, or to achieve certain creative effects.

## "Under pressure" video series

If you prefer to watch, the "Under Pressure" YouTube series explores how pressure works. It covers these concepts in detail.

{% embed url="<https://www.youtube.com/playlist?list=PLp1wHemgDmJ2kCUS7-fzfxt4d7FETdSui>" %}

## Pressure handling: pen vs tablet

* Pen:
  * Contains the pressure sensing mechanism&#x20;
* Tablets:
  * Does NOT sense pressure.
  * Determines the number of pressure levels.
  * Translates pressure information from the pen into those levels.
  * May process pressure data before sending it to the computer.&#x20;

## Pressure units

When measuring pressure, or force applied to the tip, the standard unit is **gram-force**, abbreviated as **gf**. You may occasionally see this force described as **grams** and see the unit **g** used. This is technically incorrect, since grams are a unit of mass, not force.

## Disabling pressure

Sometimes it is useful to disable pen pressure. For options, go here: [Disabling pen pressure](/drawtab/core/pressure/disable-pen-pressure.md).

## How EMR pens measure pressure

There are two different techniques. The newer one uses a pressure sensor in the pen. More here: [EMR pressure detection](/drawtab/tech/emr/emr-pressure-detection.md).

## Notes

* Pens, even of the same model, differ a little in their pressure sensitivity.&#x20;
* Pressure sensors are subject to wear. Over time, a pen may become less sensitive than it used to be. In practice, I have never noticed this in a meaningful way.