Dear Chipfryer,
Thanks for your support.
Even though i have configured -Vref and got the response as intended, I failed to fulfil my objective of getting higher resolution of measured parameter for better accuracy.
In my case always processed (Voltage divider network R1&R2) signal voltages varies from 2.6V only. There are multiple signals tapped from the source voltage of 2.6V to 220V. Now i can able to measure @ resolution of 0.0537v.
My intension is achieve better measurement resolution of 0.001V > Vmeasure >0.0001v. (Final goal)
At this step, i planned to improve the resolution from 0.0537v to 0.0268v by means of setting -Vref = 2.5V.
Theoretically everything fine, but real time implementation is not seems to be that much easier. While testing about the ADC result with -Vref = 2.5v, that is okay and good.
While i tried to integrate the measured portion (50%) with escalated portion (2.5V ie 50% certain value for each tapings for ex: 25V for 50V measurement, that node voltage never goes below 25V ) and experienced upto 0.2V deviation from the actuals which is a worst scenario for my objective.
I realized that this deviation due to any one of the following reasons.
1. -Vref is varying slightly (AMS117 2.5V with 1000 uf)
2. System reference (GND) may be slightly differ during these functionality (decoupling 4.7uf ceramic and 2 X 1000 uf)
3. Impact of sampling current (less on low voltage and significantly high on High voltage measurements)
Now decided that -Vref implementation is best for Single parameter measurement or multiple parameters with similar amplitude.
For widely varying parameter (0V to 220V) common ground reference for both ADC and Microcontroller may be the best option.
Now i have only one option to achieve my objective. Increasing ADC bit resolution to 24bits (For one stop solution for a while).
Planning to go with MCP3561 ADC and got hope after go through below links
viewtopic.php?f=76&t=22546&p=104853&hil ... 01#p104853
and FC_Comp_Source_ExternalADC_MCP356X.fcfx for FC8
https://www.flowcode.co.uk/wiki/index.p ... log_Input)
Chipfryer, i hope you can help me to add this component to FC8 (Step by step) and utilize for test the output.