A modified Direct Digital Converter for resistive sensors in bridge form

Direct Digital Converter (DDC) suitable for resistive sensor elements connected in the form of bridge provides a digital output proportional to quantity being sensed. However, such a DDC requires that all the four sensor elements are to be identical. If there is a mismatch between the sensor elements (nominal values of the four resistances not equal) the error in the output of the DDC increases drastically. We now present a modified DDC that can tolerate mismatch between the four sensing elements of a bridge type resistive sensor. While the worst case error observed from the conventional DDC scheme rises from ± 0.07% to ± 1.32 % (simulation studies) for a very low mismatch of 0.03 %, the worst case error observed from the improved DDC scheme proposed here is only ± 0.24%.