Investigating the noise of logarithmic voltage-to-code converters

Conclusions The output-code dispersion has a tendency to increase with a reduction of the input voltage.Within the input voltage range of 1–10 V, the dispersion varies in the limits of 0.3–0.7. If the maximum deviation of the code at the transducer's output is taken as 3, the error determined by the formula_rlt=3/t_max (t_max is the length of the entire transducer's scale) will amount to_rlt=2.1/10242%.Owing to the fact that at the gently-sloping segment of the exponential curve the nonlinearity becomes more pronounced with the reduction of the voltage quantum value, the distribution of the LVCC output noise passes smoothly from the normal to the logarithmically normal law.The LVCC under consideration is designed on the principle of the piecewise-exponential approximation and, therefore, the conclusion about the noise distribution according to the logarithmically normal law can be extended to all functional voltage-to-code transducers designed on that principle. In applying statistical processing of transformed-data sampling to functional pulse-time voltage-to-code transducer design on the principle of piecewise-exponential approximation it is necessary to bear in mind that the output-code distribution law is asymmetrical, and this means that the mode and median do not coincide (as a result of statistical processing, we obtain the median and not the mode which is a precise measure of the input voltage). This produces a systematic error A=Mo-Me. If the required precision is comparable to this quantity, it becomes necessary to take into account this systematic error.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 54–55, April, 1973.