What Is a Cell Phone Digitizer?

By Dan Howard

The touch screen technology featured by modern smartphones allows you to browse the Web, type on-screen and use apps by tapping with your finger or a stylus. Your cell phone uses a device called a digitizer to transform the tap into digital information. This information is stored and analyzed by the phone's CPU to determine and perform the action that your tap indicates.

Definition

A digitizer is defined as any device that detects an analog signal and converts the signal into a digital representation. The most common variety of digitizer operates by detecting when a point on a surface is touched. The digitizer stores the coordinates of the area that is touched as digital data for other devices to process.

Cell Phone Digitizer

In a cell phone with touch screen capabilities, the digitizer is an analog sensor that is placed just below the device's screen. When you touch the screen, the digitizer senses your touch and encodes it as digital information. This information includes the location that you touched. In some cases data regarding how hard you pressed the surface is also recorded.

Data Abstraction

Once the digitizer stores the touch location coordinate information then that data becomes available to the phone's processing core. The processor performs several functions on the raw digitizer data, such as comparing coordinate data over a series of time points to infer fluid movement. The processor also analyzes the coordinate data to determine what icon, button or link that you "meant" to tap on the screen. The processor receives and analyzes a constant stream of digitizer data as long as you continue to touch your cell phone's screen.

Passive Digitizers

There are two primary types of digitizers that are used in cell phones and other touch screen devices. Devices with passive digitizers have two layers of material on top of the screen. The top layer is slightly electrified. When you touch a spot on the screen, an electric charge passes to the bottom layer and is recorded by sensors at each corner of the device. These sensors calculate the location and potency of the touch based on the amount of current received at each of the four sensors. Most cell phones and other devices that don't include a stylus pen utilize passive digitizers.

Active Digitizers

Devices that demand a higher level of precision use active digitizers to capture touch information. Active digitizers generate their own magnetic field. When you touch the screen of a device with an active digitizer then you disrupt that field slightly. The device detects the field disruption and determines the point of contact and intensity of contact with a high degree of accuracy.