Linearity

Linearity is actually a special type of conformity. Linearity refers to how straight the output tracks in a linear fashion as the wiper moves from 0%-output to 100%-output.

Typically, you will get a "wavy" function as you move the wiper from one end to the other.

The linearity spec tells your customer how straight a line he would see if he were to plot the output of the potentiometer. For example, Figure 2.54 shows an actual output curve for one particular potentiometer.

There are four main ways to define linearity.

• Absolute linearity is the maximum permissible deviation of the actual output curve from a fully defined straight reference line. It is the most difficult to achieve. Figure 2.54 shows this type.



Figure 2.54

• Independent linearity is the maximum permissible deviation of the actual output curve from a reference line. This is the linearity measure that is provided for most Bourns precision potentiometers and panel controls. Figure 2.55 shows this type.

Figure 2.55

• Zero-based linearity is a special case of independent linearity in which the zero travel end of the theoretical reference line is specified. Figure 2.56 shows this type.

Figure 2.56

• Terminal-based linearity is the maximum deviation of the actual output from a straight reference line drawn through minimum and maximum endpoints. These points are separated by the actual electrical travel, rather than theoretical electrical travel. Figure 2.57 shows this type.

Figure 2.57

Figure 2.58