User Manual

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Electronic Symbol for pre-set rheostat
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A high power wirewound potentiometer.
Digital potentiometer
Main article: Digital potentiometer
A digital potentiometer (often called digipot) is an electronic component that mimics the functions of
analog potentiometers. Through digital input signals, the resistance between two terminals can be
adjusted, just as in an analog potentiometer. There are two main functional types: volatile, which
lose their set position if power is removed, and are usually designed to initialise at the minimum
position, and non-volatile, which retain their set position using a storage mechanism similar to Flash
memory or EEPROM.
Usage of a digipot is far more complex than that of a simple mechanical potentiometer, and there
are many limitations to observe; nevertheless they are widely used, often for factory adjustment and
calibration of equipment, especially where the limitations of mechanical potentiometers are
problematic. A digipot is generally immune to the effects of moderate long-term mechanical vibration
or environmental contamination, to the same extent as other semiconductor devices, and can be
secured electronically against unauthorised tampering by protecting the access to its programming
inputs by various means.
In equipment which has a microprocessor, FPGA or other functional logic which can store settings
and reload them to the "potentiometer" every time the equipment is powered up, a
multiplying DAC can be used in place of a digipot, and this can offer higher setting resolution, less
drift with temperature, and more operational flexibility.
Membrane potentiometers
A membrane potentiometer uses a conductive membrane that is deformed by a sliding element to
contact a resistor voltage divider. Linearity can range from 0.5% to 5% depending on the material,
design and manufacturing process. The repeat accuracy is typically between 0.1mm and 1.0mm with
a theoretically infinite resolution. The service life of these types of potentiometers is typically 1 million
to 20 million cycles depending on the materials used during manufacturing and the actuation
method; contact and contactless (magnetic) methods are available. Many different material
variations are available such as PET, FR4, and Kapton. Membrane potentiometer manufacturers
offer linear, rotary, and application-specific variations. The linear versions can range from 9mm to
1000mm in length and the rotary versions range from 0° to multiple full turns, with each having a
height of 0.5mm. Membrane potentiometers can be used for position sensing.
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For touch-screen devices using resistive technology, a two-dimensional membrane potentiometer
provides x and y coordinates. The top layer is thin glass spaced close to a neighboring inner layer.
The underside of the top layer has a transparent conductive coating; the surface of the layer beneath