What is the resistance tolerance of the digital potentiometers?
It is either a maximum of ±30% or ±20%. Please see datasheets. If using the pot in the 3-terminal voltage divider mode (without any series resistor), the tolerance is irrelevant because the resistances RWA and RWB are ratiometric. If using the pot in the 2 terminal rheostat mode, you should account for the worst case variation. On the AD525X family and AD5235 digipots resistance tolerance is stored in the EEPROM at factory with an accuracy of 0.1%. Thus users can retrieve the resistance tolerance and calibrate the system accordingly.
