Application of the Combined Method for the Estimation of the RMS Measurement Error Caused by ADC Nonlinearity

Currently, digital methods are applied to measure the root mean square (RMS) of the signal in most cases. To obtain instantaneous values of the input signal in digital form, an analog-to-digital converter (ADC) is applied. Real ADCs have deviations (errors) of the conversion function from the linear one. These deviations can be presented as additive, multiplicative and nonlinear. Additive and multiplicative errors can be eliminated by zero adjustment and calibration of the measurement channel, respectively. To eliminate the nonlinearity of the ADC transfer function requires individual adjustment of the measurement channel of each device. This significantly increases the cost of the device. This article describes a technique ("combined" method of representation of the ADC nonlinearity), which allows to estimate of the RMS measurement error caused by the nonlinearity of the ADC transfer function. The analytical relations allowing to perform calculation of the error estimation are obtained. The proposed approach is compared with existing techniques. Simulation mathematical modeling is performed in Matlab and Simulink software packages. This allows to evaluate the correctness of the obtained analytical relations.