Analog to Digital Converter (Magnitude and Frequency)

[tahir4awan]

We have been studying about analog to digital converter in terms of magnitude that as analog signal magnitude rises the ADC produces binary output with respect to analog signal magnitude. In digital multimeters we talk about analog signal magnitude not frequency if we are measuring voltage or current.

But in the conversion of voice signal to digital binary it is frequency that changes not magnitude if I am right.

Does it mean there are two methods of ADC one for analog signal magnitude and other for analog signal frequency?

 

[BradtheRad]

The methods are the same but the audio must be sampled much faster.

My DMM updates its display twice per second so I guess it takes a sample that often. I find that if I'm reading a changing signal, the display might show a middle value. Absence of signal is supposed to show 0 on the readout.

Audio is sampled thousands of times per second. Absence of signal is assigned the value of the number halfway between 0 and maximum.

 

[tahir4awan]

How ADC determines the increasing and decreasing magnitude of analog signal. I have seen only positive values in steps of ADC.For example if an analog signal increase from 0 to max ADC assign binary values from 0 to max but when analog signal goes from max to 0 then binary values will be used?

 

[BradtheRad]

A common sampling rate for audio ADC is 41.1 kHz. That is fast enough to obtain details of waveforms through the entire audible spectrum (more or less).

Each incoming volt level is converted to a value between -32768 and +32767 (two's complement representation). 16 bit resolution or two bytes is common.