ADS1115-Q1: The sampling data error is relatively large

Hi Neal,

thanks a lot for your question.
I believe the diagram which shows the error didn't come through. Would you mind trying to attach it again?

Regards,

Hi,

Hi Neal,

I am sorry, I think I have some issues understanding what your question is. I thought you wanted to show a diagram or table that shows what type of data error you are seeing between the measurements with the different FSR settings.
Could you please explain in more detail what error you are seeing? Or what is the input voltage you are applying and what data do you read from the ADC?

Regards,

Hi,

sorry,

Vb is sampling a negative pressure,
Initially, FSR was 101: FSR = ±0.256 V for measurement and sampling, and the data error was relatively small (ADC input voltage < 0.256V).
Now the sampling ADC input voltage is 0.7v, and FSR is configured as: 011: FSR = ± 1.024v for sampling,
but the sampling data error is large;Can't find the reason, What could have caused it?

Thanks!

Hi Neal,

could you quantify what 'relatively small' and 'large' means? E.g. do you measure 0.9V instead of 0.7V for example when you configure FSR=+/-1.024V?

The only reason that I could think of right now without knowing more specifics about the size of the error is that the input impedance of the ADC changes when changing the FSR setting as described in the Electrical Characteristics table in the datasheet. Therefore the ADC inputs will 'load' the resistive bridge differently for the different FSR settings. This could then cause different amount of measurement errors.

Regards,

Hi,

'relatively small' and 'large' is big error, small error,in test.

Thanks!

Hi Neal,

yes, that is understood. But I will need more specific information on how small or large the error is in order to help you. E.g. how many mV, codes, LSBs or % is the error in the two cases?

Regards,