Question

How the minimum sample rate is defined for sampling a signal? What would be the sampling rate for a temperature, voice, and a video signals and why?

Answer 1

How the minimum sample rate is defined for sampling rate ?

Minimum sample rate of any signal is defined by using sampling theorem which states that "If a continuous time signal does not contain frequency component higher than W Hz ,Then it can be determined by the uniform samples taken at rate f_s samples per second

Where

OR

.

The sampling rate 2 W is also known as Nyquist rate .

What would be the sampling rate for a temperature ?

Sampling rate is determined by using Nyquist criteria which states that the sampling rate must be as twice as the highest frequency component of the input signal .

But in most of the embedded control application while reading analog sensors we can not use nyquist criteria.Therefore reconstruction of input signal requires significant computational power . Thus digital signal processors are used .

For these type of applications, the maximum rate of change is  specified as a maximum slope, such as “one degree per second” for a digital thermometer.

which is converted as   (ADC units per second) through simple scaling based on the range of the ADC.Where

= Sampling rate

= difference between two successive ADC readings

is the specification of maximum slope which is also define as G

E be the maximum allowable error

What would be the sampling rate for a Voice  ?

To record Audio signal (Voice ),we use digital systems which take measurements of sound wave at certain interval.and they do this certain number of time per second and all of the discrete measurements is sample .

Therefore, the audio sample rate is the number of these measurements taken per second of audio recorded.more the samples per second higher the voice quality .Because more number of measurements give more accuracy .

Generally sample rate is determined in Hz .And the standard sample rate of audio signal is 44,100 Hz.

Speech signal sampling rate, Generally human speech,are sampled at a much lower rate almost 100 Hz–4 kHz range allowing a sampling rate of 8 kHz.

What would be the sampling rate for a Video signal ?

Sampling rate for a video signal is rather define as frame rate or field rate.The sampling frequency of image  is the repetition rate of the sensor integration period.Here integration period will be  shorter than the time between repetitions,therefore sampling frequency may be different from the inverse of sample time

For PAL video - sampling frequency = 50 Hz

For N T S C video - sampling frequency = 59.94 Hz

common pixel sampling rate is 13.5 MHz for C C I R 601 ,D 1 video .