Improved resistance to digital converter for low-value resistive sensor with lead wire compensation
Gopal Singh, Mangalanathan Umapathy, Uma Gandhi, Shiraz Sohail · 2022 IEEE Region 10 Symposium (TENSYMP) · 2022
Improved resistance to digital converter (RDC) for a low-value resistive sensor with lead resistance compensation is presented. The proposed scheme is based on the dual-slope ADC with three switches and a diode. It completes measurement in one charging-discharging cycle only, hence it provides improvement to existing RDCs, where lead compensation is not available. Moreover, it is faster compared to existing direct microcontroller interfaces (DMI) where 2 or 3 charging-discharging cycles are required. The scheme works by connecting the resistive sensor to the input terminal of the integrator of the dual-slope ADC. In the charging path (or mode), sensor resistance is present along with lead resistance; and in discharging path, sensor resistance is bypassed, and only lead resistance is there. The difference between the RC time constant during these two modes is used to find the sensor resistance. The diode is used to turn on a switch for bypassing the resistive sensor. The diode voltage drop is not there in the charging and discharging path, which is another novelty. The scheme works with low-value resistive sensors (≈ 100 Ω), a feature not found in existing RDCs. The hardware prototype of the proposed scheme on the breadboard shows a maximum error of ±0.87 % in the range of 100 Ω to 180 Ω.