Appraisal of the Effective Number of Bits of the ADC for Sensors with Account for Dynamic Errors

Abstract

The static maximum relative error of the ADC for sensors is determined by the value of its least significant bit. During the input signal conversion in the ADC the information delay causes the dynamic error, which is added to the static error and actually reduces the effective number of bits. This decrease can be estimated by the effective number of bits, which illustrates the qualitative and quantitative assessment of the additional error. The article demonstrates that the effective bits rate is defined by the delay period of information in the ADC, as well as the sampling rate of the input signal. This, in turn, requires setting the spectrographic density (SD) for the converted signal, as well as an algorithm for selecting the sampling rate. It is recommended that the delay time of the ADC includes the delay in the analog storage and amplitude multiplexer, which are located at the ADC input and are directly involved in the conversion process. The article draws attention to the fact that the real sampling rate of analog signals, chosen from the point of view of the straight task of errors distribution in the automatic control system, significantly exceeds the sampling rate according to the sampling theorem. This requires the correction of the obtained results using the sampling theorem, in the direction of reduction of effective number of bits.