Resolution

Resolution is one of the parameters that is unique to wirewound elements. There are three types of resolution, and each is a measure of the step changes in output as the wiper moves across the resistive element. For non-wirewound elements, output smoothness reflects resolution effects. Typically, non-wirewound elements are considered to have infinite resolution.

Figure 2.52

Travel resolution refers to the number of degrees it takes to rotate the shaft of the device to achieve the next incremental increase of voltage.

Voltage resolution is the greatest incremental change in output voltage in any portion of the resistance element when moving the wiper in one direction.

Figure 2.52 compares travel resolution and voltage resolution.

The typical output of a wirewound potentiometer is a staircase pattern in which the output voltage remains relatively constant for a small amount of wiper travel, then it suddenly changes.

The third type of resolution is theoretical resolution. Theoretical resolution calculates output changes with wiper movement by using the following formula:

Theoretical Resolution

In this formula, N equals the number of active turns of wire in the element.

For example, if you have an element with 10 turns, its theoretical resolution is 10%. In another example, for a TR value of 1,000 Ωs, there are approximately 172 turns of wire in the element, so the theoretical resolution is 0.58%.

Resolution is always a maximum specification.