s to conversion error. To minimize the effect of differences in the capacitor charge and discharge paths, the value ofR should be chosen to be much greater than the value of the pullup resistor. In the voltmeter application, the selected value ofR is 267 kilohms, which exceeds the value of the pullup resistor by more than an order of magnitude. The time constant (RC), which isa function of the desired converter resolution, determines the duration of the capacitorcharge/discharge cycle. The more time required for the capacitor to charge and discharge, the greater the number of samples required in the measurement loop and the greater the number of entries in the lookup table. Figure 2. Typical Capacitor Charge/DIscharge Cycle Figure 3. Capacitor Voltage Variation asa Function of RC Variation
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