User Manual

it has a transparent resistive coating. A finger or stylus deforms the glass to contact the underlying
layer. Edges of the resistive layer have conductive contacts. Locating the contact point is done by
applying a voltage to opposite edges, leaving the other two edges temporarily unconnected. The
voltage of the top layer provides one coordinate. Disconnecting those two edges, and applying
voltage to the other two, formerly unconnected, provides the other coordinate. Alternating rapidly
between pairs of edges provides frequent position updates. An analog-to digital converter provides
output data.
Advantages of such sensors are that only five connections to the sensor are needed, and the
associated electronics is comparatively simple. Another is that any material that depresses the top
layer over a small area works well. A disadvantage is that sufficient force must be applied to make
contact. Another is that the sensor requires occasional calibration to match touch location to the
underlying display. (Capacitive sensors require no calibration or contact force, only proximity of a
finger or other conductive object. However, they are significantly more complex.)
Potentiometer applications
Potentiometers are rarely used to directly control significant amounts of power (more than a watt or
so). Instead they are used to adjust the level of analog signals (for example volume controls
on audio equipment), and as control inputs for electronic circuits. For example, a light dimmer uses a
potentiometer to control the switching of a TRIAC and so indirectly to control the brightness of
lamps.
Preset potentiometers are widely used throughout electronics wherever adjustments must be made
during manufacturing or servicing.
User-actuated potentiometers are widely used as user controls, and may control a very wide variety
of equipment functions. The widespread use of potentiometers in consumer electronics declined in
the 1990s, with rotary encoders, up/down push-buttons, and other digital controls now more
common. However they remain in many applications, such as volume controls and as position
sensors.
Audio control
Linear potentiometers ("faders")
Low-power potentiometers, both linear and rotary, are used to control audio equipment, changing
loudness, frequency attenuation, and other characteristics of audio signals.
The 'log pot' is used as the volume control in audio power amplifiers, where it is also called an "audio
taper pot", because the amplitude response of the human earis approximately logarithmic. It ensures
that on a volume control marked 0 to 10, for example, a setting of 5 sounds subjectively half as loud
as a setting of 10. There is also an anti-log pot or reverse audio taper which is simply the reverse of
a logarithmic potentiometer. It is almost always used in a ganged configuration with a logarithmic
potentiometer, for instance, in an audio balance control.
Potentiometers used in combination with filter networks act as tone controls or equalizers.