Investigation of Digital Potentiometer Networks for Precise and Digital Calibration of Resistive Sensors in Wheatstone Bridges

In the sensor market resistive sensors play a significant role. These types of sensors require accurate electronics for measuring. The sensors and electronics are usually calibrated individually after production. This means that recalibration during operation is not easily possible and leads to inaccurate calibrations due to aging effects over the life cycle or changing environmental influences. Measuring bridges are suitable for measuring resistive sensors. If these are equipped with digital potentiometers, the system can be readjusted via digital communication. This enables repeating calibration of the system in the field, thus eliminating ageing effects during life cycle and environmental influences. A Wheatstone bridge is used as the basis, in which the sensor is installed in one leg. A digital potentiometer network forms the other leg and is used to calibrate the bridge. Digital potentiometers are widely used components that provides a resistance value which can be change via a digital communication interface. This allows the Wheatstone bridge to be adjusted during operation using microcontrollers. One problem that arises is the relatively low resolution of a single digital potentiometer. By this the Wheatstone bridges cannot be calibrated optimally. Various digital potentiometer networks are examined and compared in this paper, achieving a better accuracy and resolution of the calibration.