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ADC sampling rate selection

Other Parts Discussed in Thread: ADS131A04

Hi,

I am going to to design a AC mains voltage measurement system.Tthe input specifications are as given below

Input Voltage- 230Vrms 50Hz

Harmonics to be measured- up to 15th Harmonics

I need to know what should be my sampling rate to measure AC signal of 50HZ with up to 15th Harmonics.

The max input frequency is 50*15= 750Hz

As per nyquist criteria Fs min = 750*2= 1500Hz

But what should be the optimum sampling rate-  is it as per nyquist criteria or more than that.

How to find out optimum sampling frequency ? (Minimum and maximum) and how to select adc as per sampling rate specification.

Thanks and Regards,

Swaminath

  • Hi Swaminath,

    This is a very open ended question and I don't think that I can tell you what the "optimum" sampling rate would be with only the frequency of the input signal in mind as it depends on a number of factors. 

    What are the performance goals of the design? 

    How often do you need to check this measurement? (output datarate)

    How cost sensitive is the application? 

    Do you require isolation as well? 

    If you have a fixed output datarate, the advantage of increasing the sampling frequency is that the OSR (over sampling ratio) increases and leads to less noise in the measurement. For some customers, sampling at Nyquist (2x input speed) is enough, some customers want to sample at 10x, and some customers even go to 100x. 

    You can find tables that demonstrate this in many of our datasheets, table 1. of the ADS131A04 datasheet for example: http://www.ti.com/lit/ds/symlink/ads131a04.pdf