Amplitude Quantization Error
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Quantization Error - SummaryThis article explains what amplitude quantization error is and what can be done to avoid it. Typically quantization error is caused during acquisition of data. It is synonymous to rounding error. In order to
Uniform Quantization
explain this, a real time signal has been artificially modified to an extreme to show quantization example the difference between a signal sampled with adequate amplitude resolution and the same signal sampled with insufficient amplitude resolution. Also, this quantization error formula example was taken into the frequency domain to demonstrate how quantization error can affect the spectrum of the signal.The ProblemAmplitude Quantization Error is typically caused by not having sufficient amplitude resolution to accurately capture the exact
What Is Quantization
amplitude of the signal. With the modern ADC’s using 24 or even 16 bit resolution this is not typically a problem, however measurement systems with fewer bits of amplitude resolution can compromise the data.The cause of this insufficient resolution is based on the sampling of the level of a signal, or in other words, having too few bits to accurately define the signal level during the sampling process. Typically analog to digital converters
Sampling And Quantization In Digital Image Processing
have a specified voltage range which they can accept. The Prosig hardware ADC range is ±10 Volts. The ADC’s in these systems are 24-bit which means the total range of 20 Volts (±10 Volts) are 16777216 (224) different levels. This should be more than sufficient number of levels to adequately define the signal level from most transducers. To demonstrate this, I have sampled a signal with adequate amplitude resolution (Figure 1).Figure 1: Data sampled with adequate amplitude resolutionHowever, under rare circumstances if the transducer used has a very low sensitivity (e.g. 1µV/EU) and and the system gain is not adjusted to use the full ADC range, this can lead to the amplitude not having adequate resolution to accurately described the signal. If only ±1 V or less of the ±10 V available of the ADC range is used there are far fewer levels which can be used to define the signal level.Now the same data artificially modified introducing an extreme amount of rounding error is shown in Figure 2. The levels of approximately -15 EU to +12.5 EU as displayed in Figure 1 has been rounded to quantized levels of -12, -8, -4, 0, 4, 8, and 12.Figure 2: Extreme quantization (rounding error)This, of course, is an exaggeration, but it becomes visually apparent that the
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