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counting mode

In the counting method, one of many methods for A/D converters, the analog input voltage is compared in a comparator

with a stair-stepped comparison voltage. The step values of the staircase voltage correspond to the lowest possible level, which represents the highest resolution. The staircase voltage is stepped up by a counter

until the comparison voltage equals the input voltage. When the voltage equals the comparator gives a pulse which stops the staircase generator. The number of stair steps is counted and corresponds to the value of the analog input voltage.

Structure of the A/D converter according to the counting method

Structure of the A/D converter according to the counting method

Since the staircase switching is done with the lowest possible level value, the conversion time can be relatively long at higher input levels, because the staircase voltage must pass through all stages. The counting method has a lot of similarity with the slope method, except that in the slope method a sawtooth is used and the time is determined with counting pulses until the input voltage corresponds to the sawtooth voltage.

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Englisch: counting mode
Updated at: 19.12.2008
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