Data Loss in Continuous Conversion Mode with AD7177-2 Eval Software – How to Log Data Without Gaps?

Question

I am working with the AD7177-2 in continuous conversion mode and using the AD7177-2 Evaluation software. I have set the sampling mode to data logging and started sampling, but I am encountering data loss between each conversion. I need to log data continuously for 30 minutes without any loss. How can I mitigate this issue? Any suggestions or settings I should adjust? 
 
 Regards , 
 Srihari

JCCillion · Accepted Answer

Hi srihari7 , 
 It is a limitation in the Eval+ Software wherein there is a bit of an added time delay for the software to output the set # of samples. If your input is rapidly increasing then your input may have increased already before the Eval+ Software starts to gather samples again. I have replicated your setup on my end and the best results I could get is setting the number of samples to '1'. The reason is because setting the number of samples to '1' will give you a finer step change. 
 
 On another note, when a step change occurs on the analog input, the digital filters will need to settle on the new analog input. If the step-change in analog input occurs exactly at the start of a digital filter sampling period then the output code would have settled the third RDY pulse for sinc3 and fifth RDY pulse sinc5+sinc1. Each RDY pulse indicates the end of a conversion. 
 However, a step change on the analog can occur at any point in the interval between two RDY pulses, so in general, the step-change will not occur at the start of the filter sampling period. This means the output code will not have settled by the third RDY pulse but will have settled by the fourth RDY pulse in the case of sinc3. Similar would happen for sinc5+sinc1, the output code will not have settled by the fifth RDY pulse but will have settled by the sixth RDY pulse. If the input is continuously changing then the digital filter would not be able to fully settle on a fixed voltage. 
 You may also check the Virtual Eval | Analog Devices regarding the step response of the ADC. 
 Regards, 
 JC)

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Data Loss in Continuous Conversion Mode with AD7177-2 Eval Software – How to Log Data Without Gaps?