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How to calculate overall gain of AD8232?

Question asked by ANK@123 on Nov 7, 2016
Latest reply on Jan 16, 2017 by Emman.A

Hi ,

 

I am working on one application in which I am interfacing AD8232 with Nordic semiconductor's NRF52 to get ECG signal from body. I am applying 1 mVolt signal from ECG simulator to AD8232. Output of Ad8232, I am applying to ADC of nrf52 having gain of 1/6 , 12 bit resolution and reference of 0.825 volt. The output of ADC I am plotting in lab view.

 

Now at the output of ADC I am getting ECG having peak value of 2000(ADC value) and minimum value as 1100. 

 

As per datasheet of AD8232 overall gain is 1100 V/V. So accordingly, if I am applying 1mVolt as input to AD8232, input to ADC will be 1mVolt * 1100 = 1.1 volt. Now for this input ,ADC output will be calculated as (1.1 volt * 2^(12))/(6 * 0.825)

which is equal to 910.

 

So, Why I am getting ADC output as 2000 ? Can anyone help me to understand this issue? I am attaching the waveform that I got in Lab view. 

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