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Voltage Divider on ADC Differential Pi

145 Views - Created 21/06/2021

21/06/2021

Posted by:
jevers99

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Hi,

When using the ADC Differential Pi, do you have any suggestions for reading voltages outside of -2.048 - 2.048? Is it possible to add a voltage divider for examplke?

Thanks,

 

Jon

22/06/2021

Posted by:
andrew

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Location:
United Kingdom

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Hi Jon

There are two methods you can use to reduce the voltage level to work on the ADC Differential Pi.

You can use a voltage divider with the positive side going through the R1 resistor before connecting to the ADC + input and the negative connecting directly to the ADC - input. The R2 resistor connects between ADC + and ADC -.   We have a calculator you can use to get the values for R1 and R2 based on your input voltage. https://www.abelectronics.co.uk/tools/resistor-voltage-divider

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The second method is to use a fully-differential amplifier.  An op-amp circuit is more complicated than a resistor divider but it does have the advantage of a higher impedance between the + and - inputs.  Texas Instruments has a good article explaining how to use fully-differential amplifiers at https://www.ti.com/lit/an/sloa054e/sloa054e.pdf

AB Electronics UK Tech Support

39 days ago

Posted by:
BriggTrim

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Hi.... that appears reasonably agent yes. So the issue is with respect to the differential nature of the voltage perusing I'm attempting to take - the tall end of this perusing must be underneath 5v add up to (and here is 11.1v aprox.). I'm understanding that now. So, would the arrangement here be the swapping the arrange of the resistors (and the ADC examined tests) so that the 11.1v to begin with has got to pass through the bigger resistor?

39 days ago

Posted by:
andrew

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Location:
United Kingdom

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Hi

With an 11.1v input you would need resistor values of 10K for R1 and 2.2K for R2 which would give you an output voltage of 2.002V.

With this voltage divider setup you can have a positive or a negative input voltage.  A -11.1V input would give you an output voltages of -2.002V.

AB Electronics UK Tech Support

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