Practical application

AN3023

20/23

Doc ID 16113 Rev 1

4.3

Methods for precision improvement

This section presents some hardware and software methods to minimize errors that can

occur in analog-to-digital conversions.

4.3.1

Hardware methods

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selects reference voltage between input signal ranges

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gives full ADC range – minimum voltage per bit

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White noise added to measured signal

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wobbling of input signal over several bits makes it possible to use averaging (if

input signal is very stable)

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white noise gives independence from sampling frequency

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Hardware design considerations

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grounding

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reference voltage filtering

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supply filtering

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preamplifier usage

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frequency independence

4.3.2

Software methods

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Averaging samples

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averaging decreases speed but can improve accuracy

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Digital filtering (50/60 Hz suppression from DC value)

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proper sampling frequency to be set (trigger from Timer1 is useful in this case)

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software post processing to be performed on sampled data (comb filter)

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Fast Fourier Transform (FFT) for AC measurements

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shows harmonic parts in measured signal

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slower due to more computational power requirements

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Calibration of ADC—offset, gain, bit weight calibration

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decreases internal ADC errors

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internal ADC structure must be known