Toward the end of the drop life, there is little change in the surface area which diminishes the contribution of capacitance changes to the total current.

It measures very small capacitance changes, due to a finger's proximity, among electrodes in a grid buried beneath the insulating surface of the pad.

As the capacitance changes, the charge across the capacitor does change very slightly, but at audible frequencies it is sensibly constant.

As the slider moves the capacitance changes in a linear fashion and in a repeating pattern.

Long-term frequency changes are caused by changes in the oscillator elements that determine frequency, such as crystal drift, inductance changes, and capacitance changes.

For instance, a Z5U capacitor will operate from +10 C to +85 C with a capacitance change of at most +22% to 56%.

An X7R capacitor will operate from 55 C to +125 C with a capacitance change of at most 15%.

The capacitance change at every individual point on the grid can be measured to accurately determine the touch location by measuring the voltage in the other axis.

Most discrete capacitor types have more or less capacitance changes with increasing frequencies.

The capacitance changes can then be measured and correlated with the material's thickness.